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Two new photos

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  • Mitchell
    Hey everyone. I uploaded two new ronchi photo s of my mirror after 7 Hours. Still looks like a very small hill and a bit TUE. If you see anything i don t let
    Message 1 of 27 , Dec 2, 2005
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      Hey everyone. I uploaded two new ronchi photo's of my mirror
      after 7 Hours. Still looks like a very small hill and a bit TUE. If
      you see anything i don't let me know. Mitchell
    • Jerry
      It looks a little better. Can you post a picture (a drawing) of the path the center of the mirror traces over the lap as you polish? Or maybe it is the center
      Message 2 of 27 , Dec 3, 2005
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        It looks a little better.  Can you post a picture (a drawing) of the path the center of the mirror traces over the lap as you polish?

        Or maybe it is the center of the lap over the mirror.

         

        Jerry

         

        -----Original Message-----
        From: atm_free@yahoogroups.com [mailto:atm_free@yahoogroups.com] On Behalf Of Mitchell
        Sent: Friday, December 02, 2005 8:04 AM
        To: atm_free@yahoogroups.com
        Subject: [atm_free] Two new photos

         

             Hey everyone. I uploaded two new ronchi photo's of my mirror
        after 7 Hours. Still looks like a very small hill and a bit TUE. If
        you see anything i don't let me know. Mitchell




      • Mitchell
        ... the path ... Well I don t think I can draw a picture, but here is what my stroke is like... http://www.fvas.net/victor/mirror.htm scroll about 1/3 way
        Message 3 of 27 , Dec 3, 2005
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          --- In atm_free@yahoogroups.com, "Jerry" <wa4guu@b...> wrote:
          >
          > It looks a little better. Can you post a picture (a drawing) of
          the path
          > the center of the mirror traces over the lap as you polish?
          >
          > Or maybe it is the center of the lap over the mirror.
          >
          >
          >
          > Jerry
          >

          Well I don't think I can draw a picture, but here is what my stroke
          is like...

          http://www.fvas.net/victor/mirror.htm

          scroll about 1/3 way down. It's like the polishing stroke there. But
          on the way back (not pictured there) it is the same path
          but "backwards" (as in you criss-cross the old path). Thats how the
          books show it and a couple of friends drew me some pics which are
          like that. I don't know how to really describe it but i'm pretty
          sure i'm doing it correctly. Being sure to keep it 1/4 to 1/3
          diameter too. the Ronchi's don't look too much brighter because i
          had to turn the LED way down becuase it was too bright.

          >
          >
          > -----Original Message-----
          > From: atm_free@yahoogroups.com [mailto:atm_free@yahoogroups.com]
          On Behalf
          > Of Mitchell
          > Sent: Friday, December 02, 2005 8:04 AM
          > To: atm_free@yahoogroups.com
          > Subject: [atm_free] Two new photos

          Mitchell

          >
          >
          > Hey everyone. I uploaded two new ronchi photo's of my mirror
          > after 7 Hours. Still looks like a very small hill and a bit TUE.
          If
          > you see anything i don't let me know. Mitchell
          >
          >
          >
          >
          >
          > _____
          >
        • Mitchell
          ... i found a good picture this time... http://www.johnstelescopes.com/ go to the polishing section and scroll to the bottom. My stroke is like that (but only
          Message 4 of 27 , Dec 3, 2005
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            --- In atm_free@yahoogroups.com, "Mitchell" <Funnybone101@c...>
            wrote:
            >
            > --- In atm_free@yahoogroups.com, "Jerry" <wa4guu@b...> wrote:
            > >
            > > It looks a little better. Can you post a picture (a drawing) of
            > the path
            > > the center of the mirror traces over the lap as you polish?
            > >
            > > Or maybe it is the center of the lap over the mirror.
            > >
            > >
            > >
            > > Jerry
            > >

            i found a good picture this time...

            http://www.johnstelescopes.com/

            go to the polishing section and scroll to the bottom. My stroke is
            like that (but only 1/4 to 1/3 diameter of course).

            Mitchell
          • Jerry
            Hello again Mitchell. The theme of this post will be VARIATION…or a mild dose of randomness. Ok, I think I understand. You do a W and then an M going back
            Message 5 of 27 , Dec 3, 2005
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              Hello again Mitchell.  The theme of this post will be VARIATION…or a mild dose of randomness.

               

              Ok, I think I understand. You do a W and then an M going back and crossing strokes just like an M on top of the W would cross. That is good if you pay that much attention to the stroke path. But you can get the results of not exactly retracing the W on the way back if you don’ pay so much attention to the exact path and just try to average your strokes inside of a box of allowed travel. The box dimensions would be the 1/3D length and ¼ D width for example. The box dimensions can be varied a little.

               

              Do you start with the disk centered, or do you move it to one side then do the W and M back and forth across the center and then come back to center?  Either way is really ok.  And you could start centered and just work to one side and back to center.  And of course you don’t have to limit the number of forward and back strokes to two forward and back for the W and then two forward and back for the M. In fact I would say that is not good practice.  You can put in 9 or 10 forward and back strokes at each step around the barrel. And the number of strokes can vary slightly also. If you do 9 or 10 strokes left to right across the box  and 7 or 8 strokes back to the left you can’t exactly retrace your strokes.

               

              I think since you have made another lap and done some hours of work with it and have much the same shape in the mirror that it may be that you need to insert a little variation into the stroke to “break up” whatever is causing your zones. I suggest now is the time to try smooth the shape as you continue polishing. 

               

              Here are my suggestions on how to do that.  Some variation in the stroke should help minimize the zones you have now. If you concentrate on making your W pattern exactly the same every time it is assured zones will develop. This applies to the M part also but I will just say W from now on and we know that refers to the M also. It is unlikely the aones will go away unless you vary the pattern a little bit. Try not to work at being excessively precise in the length and width of the W.  lets say you are doing 1/3 diameter strokes and the W is ¼ diameter wide or 1/8 diameter off center to each side. If those are the dimensions you have chosen for the W you want that to be the average. Some strokes can be a little longer and some shorter. Occasionally going a little wider than ¼ D is ok too. Fuzz the box boundaries a little.  It won’t hurt to do some trips around the barrel with a W box of a slightly different height and width.  I suspect that you are tapering the length of the sides of the W. On average keep the left and right sides of the W the same length strokes as the center of the W.

               

               

              If you look at the outside center of curve Ronchigram, and for now just single out the center band, where the band is thin is a shorter radius of curve and where the band is wide is a longer radius.  Any two points along the band where the band is the same width also have the same radius of curve. You have a hole about ¾” in diameter in the middle with a raised rim like a crater on the Moon. That is the shortest radius area on the mirror. Work from there outward with the band width in mind and you can see your radius going longer then a little shorter again and then to a rapid change to longer and the the last 3/8 to ½ inch stays the same radius to the edge.  Overall, a parabolic like shape, shorter radius in the center and longer at the edge but with steep zones. Like a drunk trying to drive the parabolic line and weaving from one side of the line to the other. Don’t let me saying parabolic like shape cause you to think you are on your way to a parabola. A smooth oblate curve would be better now than the zoney parabolic like curve you have.   

               

              Here are some things besides extremely regular stroke patterns that could cause those rapid changes of radius. It could be that you have your pitch lap centered with the center of the central facet at the center of the lap.  That would also mean that the 6 facets around the center facet would be in regular positions from the center as would be the channel intersections and then the same for the outer facets. The spacing of your zones at least mildly hint at facet size and centered lap as a cause to me.

               

               

              Another idea to try for a while would be to stay either MOT or TOT for a while without switching. I know that this sounds opposite to variation. But it is a variation to your procedure. I would choose MOT myself, mainly to avoid astigmatism. Also switching back and forth MOT/TOT without using just the right length and width stroke pattern can cause the edge to go longer when TOT and the center to shorten when working MOT, and neither getting enough time to change the entire curve to the same radius.  The result would be similar to the shape you have.

               

              That is enough to digest for one post.

               

              It is good that you have had to dim your led. Everything else for the exposure being the same that would mean a better polish.

               

              It might be hard to measure because you might not be able to determine precisely where the center of curve is, but as best you can let me know how far inside and outside of the center of curve your Ronchigrams are. Try to get the same number of bands on the inside and outside pics and let me know how far apart they are and we can figure the center of curve is in the middle.  I can tell which way your curve is changing radius but have no idea how much without knowing how far inside or outside the Ronchigram is. I forgot. How many lines per inch is your grating?

               

              And I just saw your last post with a link to John’s Telescopes. 

               

               

               

              Remember the theme… VARIATION.  Some people call it randomness. What it does is “feather” the changes in curvature across the mirror that result from the edge of the lap or lap facets stopping at the same boundary on every set of Ws that you stroke. Feathering makes the transition in curvature take place over a longer distance.  That boils down to being smoother.

               

              Jerry

               

               

                 

               

              -----Original Message-----
              From: atm_free@yahoogroups.com [mailto:atm_free@yahoogroups.com] On Behalf Of Mitchell
              Sent: Saturday, December 03, 2005 3:40 PM
              To: atm_free@yahoogroups.com
              Subject: [atm_free] Re: Two new photos

               

              --- In atm_free@yahoogroups.com, "Jerry" <wa4guu@b...> wrote:
              >
              > It looks a little better.  Can you post a picture (a drawing) of
              the path
              > the center of the mirror traces over the lap as you polish?
              >
              > Or maybe it is the center of the lap over the mirror.
              >

              >
              > Jerry
              >

              Well I don't think I can draw a picture, but here is what my stroke
              is like...

              http://www.fvas.net/victor/mirror.htm

              scroll about 1/3 way down. It's like the polishing stroke there. But
              on the way back (not pictured there) it is the same path
              but "backwards" (as in you criss-cross the old path). Thats how the
              books show it and a couple of friends drew me some pics which are
              like that. I don't know how to really describe it but i'm pretty
              sure i'm doing it correctly. Being sure to keep it 1/4 to 1/3
              diameter too. the Ronchi's don't look too much brighter because i
              had to turn the LED way down becuase it was too bright.
                

              >
              > -----Original Message-----
              > From: atm_free@yahoogroups.com [mailto:atm_free@yahoogroups.com]
              On Behalf
              > Of Mitchell
              > Sent: Friday, December 02, 2005 8:04 AM
              > To: atm_free@yahoogroups.com
              > Subject: [atm_free] Two new photos

              Mitchell


              >
              >      Hey everyone. I uploaded two new ronchi photo's of my mirror
              > after 7 Hours. Still looks like a very small hill and a bit TUE.
              If
              > you see anything i don't let me know. Mitchell
              >
              >
              >
              >
              >
              >   _____
              >





            • Jerry
              ... From: Jerry Sent: Saturday, December 03, 2005 9:12 PM To: atm_free@yahoogroups.com Subject: RE: [atm_free] Re: Two new photos Hello again Mitchell. The
              Message 6 of 27 , Dec 3, 2005
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                -----Original Message-----
                From:
                Jerry
                Sent:
                Saturday, December 03, 2005 9:12 PM
                To:
                atm_free@yahoogroups.com
                Subject: RE: [atm_free] Re: Two new photos

                 

                Hello again Mitchell.  The theme of this post will be VARIATION…or a mild dose of randomness.

                 

                That would also mean that the 6 facets around the center facet would be in regular positions from the center

                 

                That is a typo. I meant 8 facets, the 4 corners and the 4 in between them.

                 

                Jerry


              • Mitchell
                ... a mild ... crossing ... if you pay ... results of not ... attention to ... box of ... D width ... yup, you got it. I try to keep a little variation in
                Message 7 of 27 , Dec 4, 2005
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                  --- In atm_free@yahoogroups.com, "Jerry" <wa4guu@b...> wrote:
                  >
                  > Hello again Mitchell. The theme of this post will be VARIATION…or
                  a mild
                  > dose of randomness.
                  >
                  >
                  >
                  > Ok, I think I understand. You do a W and then an M going back and
                  crossing
                  > strokes just like an M on top of the W would cross. That is good
                  if you pay
                  > that much attention to the stroke path. But you can get the
                  results of not
                  > exactly retracing the W on the way back if you don' pay so much
                  attention to
                  > the exact path and just try to average your strokes inside of a
                  box of
                  > allowed travel. The box dimensions would be the 1/3D length and ¼
                  D width
                  > for example. The box dimensions can be varied a little.

                  yup, you got it. I try to keep a little variation in there.
                  >
                  >
                  >
                  > Do you start with the disk centered, or do you move it to one side
                  then do
                  > the W and M back and forth across the center and then come back to
                  center?
                  > Either way is really ok. And you could start centered and just
                  work to one
                  > side and back to center.

                  I start with the two centered over each other, go to a side, come
                  back to center then go to the otherside and back to caenter. I do
                  this about 5 times then rotate the lap and mirror in opposite
                  dirrections.

                  And of course you don't have to limit the number
                  > of forward and back strokes to two forward and back for the W and
                  then two
                  > forward and back for the M.

                  I do usually one up then one down then one up and one down then same
                  thing back to center. i'll try to vary a little bit more.

                  In fact I would say that is not good practice.
                  > You can put in 9 or 10 forward and back strokes at each step
                  around the
                  > barrel. And the number of strokes can vary slightly also. If you
                  do 9 or 10
                  > strokes left to right across the box and 7 or 8 strokes back to
                  the left
                  > you can't exactly retrace your strokes.
                  >
                  >
                  >
                  > I think since you have made another lap and done some hours of
                  work with it
                  > and have much the same shape in the mirror that it may be that you
                  need to
                  > insert a little variation into the stroke to "break up" whatever
                  is causing
                  > your zones. I suggest now is the time to try smooth the shape as
                  you
                  > continue polishing.

                  ok. I had too add pitch to the lap becasue it was too thin (just
                  over 1/16". It should be good, for hopefully, the rest of the work
                  to be done.
                  >
                  >
                  >
                  > Here are my suggestions on how to do that. Some variation in the
                  stroke
                  > should help minimize the zones you have now. If you concentrate on
                  making
                  > your W pattern exactly the same every time it is assured zones
                  will develop.
                  > This applies to the M part also but I will just say W from now on
                  and we
                  > know that refers to the M also. It is unlikely the aones will go
                  away unless
                  > you vary the pattern a little bit. Try not to work at being
                  excessively
                  > precise in the length and width of the W. lets say you are doing
                  1/3
                  > diameter strokes and the W is ¼ diameter wide or 1/8 diameter off
                  center to
                  > each side. If those are the dimensions you have chosen for the W
                  you want
                  > that to be the average. Some strokes can be a little longer and
                  some
                  > shorter. Occasionally going a little wider than ¼ D is ok too.
                  Fuzz the box
                  > boundaries a little. It won't hurt to do some trips around the
                  barrel with
                  > a W box of a slightly different height and width. I suspect that
                  you are
                  > tapering the length of the sides of the W. On average keep the
                  left and
                  > right sides of the W the same length strokes as the center of the
                  W.


                  ok, i'll do my best do put some variation like you mentioned above
                  into my stroke.


                  >
                  > If you look at the outside center of curve Ronchigram, and for now
                  just
                  > single out the center band, where the band is thin is a shorter
                  radius of
                  > curve and where the band is wide is a longer radius. Any two
                  points along
                  > the band where the band is the same width also have the same
                  radius of
                  > curve. You have a hole about ¾" in diameter in the middle with a
                  raised rim
                  > like a crater on the Moon. That is the shortest radius area on the
                  mirror.
                  > Work from there outward with the band width in mind and you can
                  see your
                  > radius going longer then a little shorter again and then to a
                  rapid change
                  > to longer and the the last 3/8 to ½ inch stays the same radius to
                  the edge.
                  > Overall, a parabolic like shape, shorter radius in the center and
                  longer at
                  > the edge but with steep zones. Like a drunk trying to drive the
                  parabolic
                  > line and weaving from one side of the line to the other. Don't let
                  me saying
                  > parabolic like shape cause you to think you are on your way to a
                  parabola. A
                  > smooth oblate curve would be better now than the zoney parabolic
                  like curve
                  > you have.
                  >
                  >
                  >
                  > Here are some things besides extremely regular stroke patterns
                  that could
                  > cause those rapid changes of radius. It could be that you have
                  your pitch
                  > lap centered with the center of the central facet at the center of
                  the lap.

                  no the facets are off set.


                  > That would also mean that the 6 facets around the center facet
                  would be in
                  > regular positions from the center as would be the channel
                  intersections and
                  > then the same for the outer facets. The spacing of your zones at
                  least
                  > mildly hint at facet size and centered lap as a cause to me.
                  >
                  >
                  >
                  >
                  >
                  > Another idea to try for a while would be to stay either MOT or TOT
                  for a
                  > while without switching. I know that this sounds opposite to
                  variation. But
                  > it is a variation to your procedure. I would choose MOT myself,
                  mainly to
                  > avoid astigmatism. Also switching back and forth MOT/TOT without
                  using just
                  > the right length and width stroke pattern can cause the edge to go
                  longer
                  > when TOT and the center to shorten when working MOT, and neither
                  getting
                  > enough time to change the entire curve to the same radius. The
                  result would
                  > be similar to the shape you have.
                  >
                  >
                  >
                  > That is enough to digest for one post.
                  >
                  >
                  >
                  > It is good that you have had to dim your led. Everything else for
                  the
                  > exposure being the same that would mean a better polish.
                  >
                  >
                  >
                  > It might be hard to measure because you might not be able to
                  determine
                  > precisely where the center of curve is, but as best you can let me
                  know how
                  > far inside and outside of the center of curve your Ronchigrams
                  are. Try to
                  > get the same number of bands on the inside and outside pics and
                  let me know
                  > how far apart they are and we can figure the center of curve is in
                  the
                  > middle. I can tell which way your curve is changing radius but
                  have no idea
                  > how much without knowing how far inside or outside the Ronchigram
                  is. I
                  > forgot. How many lines per inch is your grating?

                  ok. I'll perform that test today and get back to you tonight. My
                  grating is 85 L/per inch.

                  >
                  >
                  >
                  > And I just saw your last post with a link to John's Telescopes.
                  >
                  >
                  >
                  >
                  >
                  >
                  >
                  > Remember the theme… VARIATION. Some people call it randomness.
                  What it does
                  > is "feather" the changes in curvature across the mirror that
                  result from the
                  > edge of the lap or lap facets stopping at the same boundary on
                  every set of
                  > Ws that you stroke. Feathering makes the transition in curvature
                  take place
                  > over a longer distance. That boils down to being smoother.

                  i understand.

                  >
                  >
                  >
                  > Jerry

                  Clear Dark skies,

                  Mitchell
                • Mitchell
                  ... a mild ... would be in ... between them. ... actually that might be a bit differen t because my new lap only has 4 channels each way. Before when there was
                  Message 8 of 27 , Dec 4, 2005
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                    --- In atm_free@yahoogroups.com, "Jerry" <wa4guu@b...> wrote:
                    >
                    >
                    >
                    >
                    >
                    > -----Original Message-----
                    > From: Jerry
                    > Sent: Saturday, December 03, 2005 9:12 PM
                    > To: atm_free@yahoogroups.com
                    > Subject: RE: [atm_free] Re: Two new photos
                    >
                    >
                    >
                    > Hello again Mitchell. The theme of this post will be VARIATION.or
                    a mild
                    > dose of randomness.
                    >
                    >
                    >
                    > That would also mean that the 6 facets around the center facet
                    would be in
                    > regular positions from the center
                    >
                    >
                    >
                    > That is a typo. I meant 8 facets, the 4 corners and the 4 in
                    between them.
                    >
                    >
                    >
                    > Jerry
                    >
                    > _____
                    >

                    actually that might be a bit differen't because my new lap only has
                    4 channels each way. Before when there was 5 the edge ones were so
                    far to the edge i was nearly beveling so i didn't add a 5th one each
                    way this time. i'll put a pic up soon. Mitchell
                  • zway2bisfancyfree
                    ... Hi Mitchell; You are doing a good job with the polishing. The contrast and definition of the Ronchi screen is really starting to show up well. Your
                    Message 9 of 27 , Dec 7, 2005
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                      --- In atm_free@yahoogroups.com, "Mitchell" <Funnybone101@c...> wrote:
                      >
                      > Hey everyone. I uploaded two new ronchi photo's of my mirror
                      > after 7 Hours. Still looks like a very small hill and a bit TUE. If
                      > you see anything i don't let me know. Mitchell
                      >


                      Hi Mitchell; You are doing a good job with the polishing. The
                      contrast and definition of the Ronchi screen is really starting to
                      show up well. Your folder just has the two latest images in it. I
                      didn't save the first set so its hard to judge how the surface is
                      changing.

                      I got a little confused with your polishing description. Are you
                      using the Normal stroke. 1/4 to 1/4 center over center back and
                      forth with no side to side motion? I think this is the best for
                      getting a sphere and removing any zoning. I would think after 7
                      hours yours would be a little closer but it is hard to tell without
                      seeing the progression of pictures.

                      Are you using mirror on top? Tool on top? Or both?
                      How hard are you pushing down? Is the weight of the mirror/tool
                      doing all the work or are you using downward force?

                      You will get a sphere faster with some down pressure but the more
                      pressure you use the higher the chance of getting scratches.



                      Good Luck
                      Dave
                    • Mitchell
                      ... mirror ... If ... I ... without ... sorry, i deleted the originals to save space i ll put them back up soon. I m using the 1/4 stroke WITH side to side
                      Message 10 of 27 , Dec 7, 2005
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                        --- In atm_free@yahoogroups.com, "zway2bisfancyfree"
                        <dmhakenewerth@n...> wrote:
                        >
                        > --- In atm_free@yahoogroups.com, "Mitchell" <Funnybone101@c...>
                        wrote:
                        > >
                        > > Hey everyone. I uploaded two new ronchi photo's of my
                        mirror
                        > > after 7 Hours. Still looks like a very small hill and a bit TUE.
                        If
                        > > you see anything i don't let me know. Mitchell
                        > >
                        >
                        >
                        > Hi Mitchell; You are doing a good job with the polishing. The
                        > contrast and definition of the Ronchi screen is really starting to
                        > show up well. Your folder just has the two latest images in it.
                        I
                        > didn't save the first set so its hard to judge how the surface is
                        > changing.
                        >
                        > I got a little confused with your polishing description. Are you
                        > using the Normal stroke. 1/4 to 1/4 center over center back and
                        > forth with no side to side motion? I think this is the best for
                        > getting a sphere and removing any zoning. I would think after 7
                        > hours yours would be a little closer but it is hard to tell
                        without
                        > seeing the progression of pictures.

                        sorry, i deleted the originals to save space i'll put them back up
                        soon. I'm using the 1/4 stroke WITH side to side motion. i'll try
                        with out side to side maybe.
                        >
                        > Are you using mirror on top? Tool on top? Or both?
                        > How hard are you pushing down? Is the weight of the mirror/tool
                        > doing all the work or are you using downward force?

                        i do both MOT and TOW, 15 min each then press. I apply a bit of
                        weight to which ever is on to but not all that much.

                        >
                        > You will get a sphere faster with some down pressure but the more
                        > pressure you use the higher the chance of getting scratches.

                        true. Thanks alot for your help!
                        >
                        >
                        >
                        > Good Luck
                        > Dave
                        >

                        thanks.

                        P.S. sorry i didn't get back to you jerry was working on a science
                        project (newtons three laws, presented it today, got an A :). I need
                        a day to rest (really tired) then i'll preform those tests you were
                        gracious enough to type up.

                        Mitchell
                      • Richard F.L.R. Snashall
                        ... Newton s Law. The mirror ground you down... so now you re going to stay at rest!;-(
                        Message 11 of 27 , Dec 7, 2005
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                          Mitchell wrote:

                          >
                          >
                          >P.S. sorry i didn't get back to you jerry was working on a science
                          >project (newtons three laws, presented it today, got an A :). I need
                          >a day to rest (really tired) then i'll preform those tests you were
                          >gracious enough to type up.
                          >
                          Newton's Law. The mirror ground you down... so now you're going
                          to stay at rest!;-(
                        • zway2bisfancyfree
                          ... Hi Mitchell, I think you will see a big improvement to the sphere if you just use a back and forth motion. Try I session and see what you think. You the
                          Message 12 of 27 , Dec 8, 2005
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                            > i do both MOT and TOW, 15 min each then press. I apply a bit of
                            > weight to which ever is on to but not all that much.
                            >


                            Hi Mitchell, I think you will see a big improvement to the sphere if
                            you just use a back and forth motion. Try I session and see what you
                            think.

                            You the same amount of pressure. Don't change anything except the
                            motion.

                            Good Luck
                            Dave
                          • talquence
                            Mitchell When you press your mirror especially with the tool on top you might try this: take a wooden disk and one of those freezer jell bags; place the jell
                            Message 13 of 27 , Dec 9, 2005
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                              Mitchell
                              When you press your mirror especially with the tool on top you might
                              try this: take a wooden disk and one of those freezer jell bags; place
                              the jell bag on the mirror/tool;place the disk on top of it; and your
                              weight on top of that. This arrangement distributes the preasure evenly
                              over the surface of the mirror. For larger mirrors I take two disks of
                              ten mil plastic, tape the outer edges together with a straw tapped in,
                              fill them with water through the staw and seal the straw. Sometimes I
                              get leaks. The disk must be stabalized to centre over the mirror-tool.
                              Make sure the bottom item is evenly supported on a realy flat surface
                              (rubber backed carpet?) during pressing. If your weight is small and
                              centred on your mirror when removed the lap will spring back creating a
                              hill in the centre when you polish.
                              talquence
                            • Mitchell
                              ... might ... place ... your ... evenly ... disks of ... in, ... Sometimes I ... tool. ... surface ... and ... creating a ... thanks for the advice. I will try
                              Message 14 of 27 , Dec 11, 2005
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                                --- In atm_free@yahoogroups.com, "talquence" <talquence@y...> wrote:
                                >
                                > Mitchell
                                > When you press your mirror especially with the tool on top you
                                might
                                > try this: take a wooden disk and one of those freezer jell bags;
                                place
                                > the jell bag on the mirror/tool;place the disk on top of it; and
                                your
                                > weight on top of that. This arrangement distributes the preasure
                                evenly
                                > over the surface of the mirror. For larger mirrors I take two
                                disks of
                                > ten mil plastic, tape the outer edges together with a straw tapped
                                in,
                                > fill them with water through the staw and seal the straw.
                                Sometimes I
                                > get leaks. The disk must be stabalized to centre over the mirror-
                                tool.
                                > Make sure the bottom item is evenly supported on a realy flat
                                surface
                                > (rubber backed carpet?) during pressing. If your weight is small
                                and
                                > centred on your mirror when removed the lap will spring back
                                creating a
                                > hill in the centre when you polish.
                                > talquence
                                >

                                thanks for the advice. I will try pressing like that. I make sure
                                the surface (some grip mat table stuff) is level. I'm uploading some
                                pictures right now. after 20 min of A Lot of "random ness" jerry
                                recomended the mirror looks much better (to me anyway.

                                Thanks Again!

                                Mitchell
                              • Jerry
                                I think it looks a little better. Do some more. ... From: atm_free@yahoogroups.com [mailto:atm_free@yahoogroups.com] On Behalf Of Mitchell Sent: Sunday,
                                Message 15 of 27 , Dec 11, 2005
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                                  I think it looks a little better.  Do some more.

                                   

                                   

                                   

                                  -----Original Message-----
                                  From: atm_free@yahoogroups.com [mailto:atm_free@yahoogroups.com] On Behalf Of Mitchell
                                  Sent: Sunday, December 11, 2005 12:43 PM
                                  To: atm_free@yahoogroups.com
                                  Subject: [atm_free] Re: Two new photos

                                   

                                  --- In atm_free@yahoogroups.com, "talquence" <talquence@y...> wrote:
                                  >
                                  > Mitchell
                                  > When you press your mirror especially with the tool on top you
                                  might
                                  > try this: take a wooden disk and one of those freezer jell bags;
                                  place
                                  > the jell bag on the mirror/tool;place the disk on top of it; and
                                  your
                                  > weight on top of that. This arrangement distributes the preasure
                                  evenly
                                  > over the surface of the mirror. For larger mirrors I take two
                                  disks of
                                  > ten mil plastic, tape the outer edges together with a straw tapped
                                  in,
                                  > fill them with water through the staw and seal the straw.
                                  Sometimes I
                                  > get leaks. The disk must be stabalized to centre over the mirror-
                                  tool.
                                  > Make sure  the bottom item is evenly supported on a realy flat
                                  surface
                                  > (rubber backed carpet?) during pressing. If your weight is small
                                  and
                                  > centred on your mirror when removed the lap will spring back
                                  creating a
                                  > hill in the centre when you polish.
                                  > talquence
                                  >

                                  thanks for the advice. I will try pressing like that. I make sure
                                  the surface (some grip mat table stuff) is level. I'm uploading some
                                  pictures right now. after 20 min of A Lot of "random ness" jerry
                                  recomended the mirror looks much better (to me anyway.

                                  Thanks Again!

                                  Mitchell






                                • Mitchell
                                  ... will do. Also figured out why the mirror and lap were sticking, forgot to wash the turpentine residue off the mirror and it was on the tool, came off when
                                  Message 16 of 27 , Dec 11, 2005
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                                    --- In atm_free@yahoogroups.com, "Jerry" <wa4guu@b...> wrote:
                                    >
                                    > I think it looks a little better. Do some more.

                                    will do. Also figured out why the mirror and lap were sticking,
                                    forgot to wash the turpentine residue off the mirror and it was on
                                    the tool, came off when i rubbed it with my fingers under some water
                                    for a bit. all set to go now. But first i'm going down to tinton
                                    falls tomarrow for the ATM meeting there (guys name is gordon..
                                    always forget the last name, but you may know who i mean). I was
                                    supposed to go last week but it got cancelled due to the snow here.
                                    talk to you all soon.

                                    Thanks again

                                    Mitch

                                    >
                                    >
                                    >
                                    >
                                    >
                                    >
                                    >
                                    > -----Original Message-----
                                    > From: atm_free@yahoogroups.com [mailto:atm_free@yahoogroups.com]
                                    On Behalf
                                    > Of Mitchell
                                    > Sent: Sunday, December 11, 2005 12:43 PM
                                    > To: atm_free@yahoogroups.com
                                    > Subject: [atm_free] Re: Two new photos
                                    >
                                    >
                                    >
                                    > --- In atm_free@yahoogroups.com, "talquence" <talquence@y...>
                                    wrote:
                                    > >
                                    > > Mitchell
                                    > > When you press your mirror especially with the tool on top you
                                    > might
                                    > > try this: take a wooden disk and one of those freezer jell bags;
                                    > place
                                    > > the jell bag on the mirror/tool;place the disk on top of it; and
                                    > your
                                    > > weight on top of that. This arrangement distributes the preasure
                                    > evenly
                                    > > over the surface of the mirror. For larger mirrors I take two
                                    > disks of
                                    > > ten mil plastic, tape the outer edges together with a straw
                                    tapped
                                    > in,
                                    > > fill them with water through the staw and seal the straw.
                                    > Sometimes I
                                    > > get leaks. The disk must be stabalized to centre over the mirror-
                                    > tool.
                                    > > Make sure the bottom item is evenly supported on a realy flat
                                    > surface
                                    > > (rubber backed carpet?) during pressing. If your weight is small
                                    > and
                                    > > centred on your mirror when removed the lap will spring back
                                    > creating a
                                    > > hill in the centre when you polish.
                                    > > talquence
                                    > >
                                    >
                                    > thanks for the advice. I will try pressing like that. I make sure
                                    > the surface (some grip mat table stuff) is level. I'm uploading
                                    some
                                    > pictures right now. after 20 min of A Lot of "random ness" jerry
                                    > recomended the mirror looks much better (to me anyway.
                                    >
                                    > Thanks Again!
                                    >
                                    > Mitchell
                                    >
                                    >
                                    >
                                    >
                                    >
                                    >
                                    >
                                    >
                                    > SPONSORED LINKS
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                                  • Mitchell
                                    ... Well i went down to tinton falls last night to gordons shop. Being he is a mirror maker by profession he has all the goodies :) Anyway, we tester my mirror
                                    Message 17 of 27 , Dec 13, 2005
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                                      --- In atm_free@yahoogroups.com, "Jerry" <wa4guu@b...> wrote:
                                      >
                                      > I think it looks a little better. Do some more.

                                      Well i went down to tinton falls last night to gordons shop. Being
                                      he is a mirror maker by profession he has all the goodies :)

                                      Anyway, we tester my mirror on his tester. There is a camera with
                                      adjustable zoom lens where your eye goes so you view it on a
                                      television where you can ajust contrast, gain, etc.

                                      The diagnosis...

                                      Large hole in the center. around 1 wave of TDE. He showed me what i
                                      was doing wrong with my stroke and i'll correct.

                                      This includes not using enough pressure, that why AFTER 7 HOURS, i'm
                                      only about 1/4 way polished out, the lazer doesn't lie.

                                      A friend of mine who has put in 30 hours of polishing on his 12" has
                                      to go back to 120. Astigmatism, alot, and some other stuff. They
                                      figured out why.

                                      We were joking though the whole night about our nice "ash trays" :P

                                      Mean while someone brought and old comercial mirror, can't remeber
                                      the company off hand, but it tested to around 1/95 wave! with a
                                      buffer of 10% or so i think it was 1/40, the best was 1/125. Quite
                                      amazing.

                                      Anyway, i'll see you guys in another seven hours :)

                                      I'll be down stairs like a hermit till i'm near done :)

                                      Mitch
                                    • Jerry
                                      Well, it sounds like you are doing OK Mitchell. Yep! You sure have a hole in the middle... and a TDE but on the other hand you could look at the shape as being
                                      Message 18 of 27 , Dec 13, 2005
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                                        Well, it sounds like you are doing OK Mitchell.

                                         

                                        Yep! You sure have a hole in the middle….. and a TDE but on the other hand you could look at the shape as being two raised rings. One just outside the hole and one just inside the edge.  But it is too soon to worry about the shape except for knowing that it is within range to fix by polishing. One wave of TDE or other error is no problem at this stage.

                                         

                                        It is good that you have someone to give advice in person. Did you take your pitch lap with you to show Gordon?  That would be helpful.  At least maybe he could show you pitch of the correct hardness.

                                         

                                        Encourage your friend to stick with the 12 inch.  It can be discouraging to put 30 hours of polishing in to find that you have to go back to grinding. Don’t let him use that thing for an ashtray until he finishes it.  Hey!  How old are you?  Aren’t you too young to be smoking?

                                         

                                        Put some hours of polishing in, but do post a picture now and then.  I would like to see how fast the shape changes when you do the stroke Gordon showed you.

                                         

                                         Jerry

                                         

                                         

                                        -----Original Message-----
                                        From:  Mitchell

                                        Well i went down to tinton falls last night to gordons shop. Being
                                        he is a mirror maker by profession he has all the goodies :)

                                        Anyway, we tester my mirror on his tester. There is a camera with
                                        adjustable zoom lens where your eye goes so you view it on a
                                        television where you can ajust contrast, gain, etc.

                                        The diagnosis...

                                        Large hole in the center. around 1 wave of TDE. He showed me what i
                                        was doing wrong with my stroke and i'll correct.

                                        This includes not using enough pressure, that why AFTER 7 HOURS, i'm
                                        only about 1/4 way polished out, the lazer doesn't lie.

                                        A friend of mine who has put in 30 hours of polishing on his 12" has
                                        to go back to 120. Astigmatism, alot, and some other stuff. They
                                        figured out why.

                                        We were joking though the whole night about our nice "ash trays" :P

                                        Mean while someone brought and old comercial mirror, can't remeber
                                        the company off hand, but it tested to around 1/95 wave! with a
                                        buffer of 10% or so i think it was 1/40, the best was 1/125. Quite
                                        amazing.

                                        Anyway, i'll see you guys in another seven hours :)

                                        I'll be down stairs like a hermit till i'm near done :)

                                        Mitch


                                         

                                      • Mitchell
                                        ... other hand ... outside the ... about the ... polishing. One ... take your ... least maybe ... yup I brought my lap. He confirmed all our discussion, it s
                                        Message 19 of 27 , Dec 13, 2005
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                                          --- In atm_free@yahoogroups.com, "Jerry" <wa4guu@b...> wrote:
                                          >
                                          > Well, it sounds like you are doing OK Mitchell.
                                          >
                                          >
                                          >
                                          > Yep! You sure have a hole in the middle... and a TDE but on the
                                          other hand
                                          > you could look at the shape as being two raised rings. One just
                                          outside the
                                          > hole and one just inside the edge. But it is too soon to worry
                                          about the
                                          > shape except for knowing that it is within range to fix by
                                          polishing. One
                                          > wave of TDE or other error is no problem at this stage.
                                          >
                                          >
                                          >
                                          > It is good that you have someone to give advice in person. Did you
                                          take your
                                          > pitch lap with you to show Gordon? That would be helpful. At
                                          least maybe
                                          > he could show you pitch of the correct hardness.

                                          yup I brought my lap. He confirmed all our discussion, it's Acculap.
                                          Speaking of my lap, since it appears i will have to do atleast
                                          another 7 hours, what about a lap mold? like the ones sold here...

                                          http://www.pitchlaps.com/


                                          > Encourage your friend to stick with the 12 inch. It can be
                                          discouraging to
                                          > put 30 hours of polishing in to find that you have to go back to
                                          grinding.
                                          > Don't let him use that thing for an ashtray until he finishes it.
                                          Hey! How
                                          > old are you? Aren't you too young to be smoking?

                                          We encourage each other, we won't give up. I find as my mirror
                                          progresses, so does my patience :) As for the smoking, it was just a
                                          joke, we don't smoke :)
                                          >
                                          > Put some hours of polishing in, but do post a picture now and
                                          then. I would
                                          > like to see how fast the shape changes when you do the stroke
                                          Gordon showed
                                          > you.

                                          the stroke i was refering to was basically 1/3 coc, with no side to
                                          side movement that i was doing before, someone else here also
                                          suggested it.

                                          Mitch

                                          >
                                          >
                                          >
                                          > Jerry
                                        • Jerry
                                          Some people use those molds. I don t think you can re-channel with the mold, so you would have to trim the lap anyway. The facet dimensions will change as
                                          Message 20 of 27 , Dec 13, 2005
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                                            Some people use those molds. I don’t think you can “re-channel” with the mold, so you would have to trim the lap anyway.  The facet dimensions will change as you work and press.  So I think you can only use the mold when you make the lap.

                                             

                                            I used a similar thing 30 years ago.  It was a hard rubber grid.  I used it once.  I didn’t like it. I channel and trim with a single edge razor.  I’m good at it so see no reason to do it any other way. It gives me more control over depth of channel and size of facet. I’ll bet I am one of only a few still doing it with a razor blade.

                                             

                                            I would say wait until you are making a larger mirror, say 10 or 12 inches or larger. If there were an advantage to using it you would not realize it on a 6 inch lap. Even a 10 inch does not require much work to cut channels.

                                             

                                            Spend the money on pitch.  You can really make a lap with that.

                                             

                                             

                                            -----Original Message-----
                                            From:  Mitchell
                                             
                                            yup I brought my lap. He confirmed all our discussion, it's Acculap.
                                            Speaking of my lap, since it appears i will have to do atleast
                                            another 7 hours, what about a lap mold? like the ones sold here...

                                            http://www.pitchlaps.com/

                                             

                                            Yep! And he recommended more pressure too.

                                             

                                            the stroke i was refering to was basically 1/3 coc, with no side to
                                            side movement that i was doing before, someone else here also
                                            suggested it.

                                            Mitch

                                             

                                            After you do a couple of hours of polishing take another picture.  And one of your new lap also. 

                                             

                                            Jerry

                                             

                                          • Bob May
                                            I ve got access to one off those laps and they do work well for making pitch laps. Just pour the pitch on the lap, covering the mold and put it on the mirror
                                            Message 21 of 27 , Dec 13, 2005
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                                              I've got access to one off those laps and they do work well for
                                              making pitch laps. Just pour the pitch on the lap, covering the
                                              mold and put it on the mirror to get the shape and then put the
                                              lap base on top and wait for it to cool. The lap does need to be
                                              warmed again to make an exact match to the mirror and then you're
                                              ready to go.
                                              Bob May
                                              bobmay at nethere.com
                                              http: slash /nav.to slash bobmay
                                              http: slash /bobmay dot astronomy.net
                                              Replace the obvious words with the proper character.
                                            • Mitchell
                                              ... with the ... dimensions will ... mold when you ... hm. Ok, i ll definitly ponder this. When i was there they were sort of showing me the afvantages of a
                                              Message 22 of 27 , Dec 14, 2005
                                              • 0 Attachment
                                                --- In atm_free@yahoogroups.com, "Jerry" <wa4guu@b...> wrote:
                                                >
                                                > Some people use those molds. I don't think you can "re-channel"
                                                with the
                                                > mold, so you would have to trim the lap anyway. The facet
                                                dimensions will
                                                > change as you work and press. So I think you can only use the
                                                mold when you
                                                > make the lap.

                                                hm. Ok, i'll definitly ponder this. When i was there they were sort
                                                of showing me the afvantages of a mold. I thought it would be nice
                                                for a larger lap, like you said, but since i still have another
                                                seven hours or so...
                                                >
                                                >
                                                >
                                                > I used a similar thing 30 years ago. It was a hard rubber grid.
                                                I used it
                                                > once. I didn't like it. I channel and trim with a single edge
                                                razor. I'm
                                                > good at it so see no reason to do it any other way. It gives me
                                                more control
                                                > over depth of channel and size of facet. I'll bet I am one of only
                                                a few
                                                > still doing it with a razor blade.

                                                I usually use a soldering iron with a large brass (clean) screwhead
                                                to melt through the pitch, works quite well.
                                                >
                                                >
                                                >
                                                > I would say wait until you are making a larger mirror, say 10 or
                                                12 inches
                                                > or larger. If there were an advantage to using it you would not
                                                realize it
                                                > on a 6 inch lap. Even a 10 inch does not require much work to cut
                                                channels.

                                                hm.
                                                >
                                                >
                                                >
                                                > Spend the money on pitch. You can really make a lap with that.
                                                >

                                                lol, yes i suppose you can.

                                                Mitch

                                                >
                                                >
                                                > -----Original Message-----
                                                > From: Mitchell
                                                >
                                                > yup I brought my lap. He confirmed all our discussion, it's
                                                Acculap.
                                                > Speaking of my lap, since it appears i will have to do atleast
                                                > another 7 hours, what about a lap mold? like the ones sold here...
                                                >
                                                > <http://www.pitchlaps.com/> http://www.pitchlaps.com/
                                                >
                                                >
                                                >
                                                >
                                                >
                                                > Yep! And he recommended more pressure too.
                                                >
                                                >
                                                >
                                                > the stroke i was refering to was basically 1/3 coc, with no side
                                                to
                                                > side movement that i was doing before, someone else here also
                                                > suggested it.
                                                >
                                                > Mitch
                                                >
                                                >
                                                >
                                                > After you do a couple of hours of polishing take another picture.
                                                And one
                                                > of your new lap also.
                                                >
                                                >
                                                >
                                                > Jerry
                                                >
                                              • talquence
                                                Mitchell I tried a square facet mold but ended up using a knife to channel until I obtained the following book. I obtained good results using this type of
                                                Message 23 of 27 , Dec 14, 2005
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                                                  Mitchell
                                                  I tried a square facet mold but ended up using a knife to
                                                  channel until I obtained the following book. I obtained good results
                                                  using this type of mold.
                                                  The following article from MAKING YOUR OWN TELESCOPE by Lllyn
                                                  J. Thompson publishedin1947 may be of interest to you and others.
                                                  A Better Lap. The channeled pitch lap just discussed is the
                                                  conventional one used by both amateur and professional mirror makers
                                                  in the past. The one about to be described (Fig. 28) originated at
                                                  Pennsylvania State College. Introduced into the Amateur Astronomers
                                                  Association workshop at the Hayden Planetarium by the author, it has
                                                  been coming into general favor. The amount of effort involved in
                                                  making the rubber mold may appear to be unreasonably out of
                                                  proportion to the result, but experience has demonstrated that the
                                                  time spent will pay dividends.

                                                  Fig. 28. The molded lap. At left is the perforated rubber mat centered

                                                  on the fine-ground face of the mirror, ready for the pitch to be
                                                  poured.

                                                  At right is a- finished lap.

                                                  Contact is easily made and kept; the lap polishes faster than the
                                                  channeled lap; and it responds more agreeably to the figuring
                                                  strokes. The reservoir of water and polishing agent surrounding the
                                                  facets tends to equalize temperatures and retard evaporation, with
                                                  the result that turneddown edge rarely occurs. Because of the
                                                  considerably smaller areas of the individual facets, a somewhat
                                                  harder pitch than that used for the conventional lap is employed.
                                                  Less than a third of the usual amount of pitch is needed, and the
                                                  rubber mold will make innumerable laps.
                                                  Sheet rubber, about 7" square and 1/16" thick, will do for the mold,
                                                  the pattern for which is shown in Fig. 29. A saddler's punch, of 3/g"
                                                  to 7/16" diameter, or a No. 4 cork borer, is a good size for making
                                                  the holes. The radius of the horizontal arcs shown is 24", but
                                                  straight lines, rather than curved, might just as well be used. The
                                                  separations given are for 3/8" holes, and should be suitably varied
                                                  for a punch of different size. The pattern is first laid out on a
                                                  sheet of thin paper, and a 6" circle then drawn, encompassing as many
                                                  whole small circles as possible. The pattern is then pasted to the
                                                  rubber mat with mucilage. When dry, the mat is laid on a thick
                                                  magazine and the holes are punched out. To cut out the partial holes
                                                  on the periphery of the 6" circle, lay the mat over the edge of a
                                                  board, with the periphery of the circle and the board's edge
                                                  coincident. By placing the punch carefully over a circle there, an
                                                  arc of any size can be cut, and the segment of rubber cut out with a
                                                  knife or razor blade. Trim the mat to within I/~" of the holes.
                                                  Remnants of the paper pattern can be removed by soaking the mat in
                                                  water.

                                                  Fig. 29. The pattern of the mat for a 6" lap, with 3/8" perforations.

                                                  Vertical lines are spaced 7/32" apart. Figures at the right indicate
                                                  separations between horizontal arcs (straight lines will do as well)
                                                  in 64ths of an inch.
                                                  top to bottom
                                                  23,23,24,25,26,27,28,30,30,28,27,26,25,23,23

                                                  The operation of making the lap is best done on top of a scrap piece
                                                  of windowpane or other sheet glass. So that the facets will not
                                                  squeeze down quickly, the pitch for this lap should be on the hard
                                                  side. When melted, the pitch should be removed from the stove and
                                                  allowed to cool briefly, and be thoroughly stirred before pouring.
                                                  Have the mirror and tool in a pail of hot water while the pitch is
                                                  melting. Lay the mat on the clean sheet of glass, and paint it all
                                                  over with a light creamy mixture of rouge' and water. While the pitch
                                                  is cooling, remove the mirror from the hot water and dry it, then
                                                  place it on the sheet of glass, face up, and paint its surface and
                                                  sides with rouge. Lay the rouge-coated rubber mat on it, carefully
                                                  centered. Take the tool from the hot water, dry it and place it
                                                  nearby, convex side down. Quickly pour the hot pitch over the mat,
                                                  starting at the center and spiraling outward nearly to the edge.
                                                  Then, carefully centering the warm tool convex side down over the
                                                  mirror, set it onto the pitch and press it firmly down to the rubber
                                                  mat, squeezing the excess pitch out over the sides. After about a
                                                  minute, invert the disks, and after a similar wait, slide the mirror
                                                  off. Allowing sufficient time for the pitch to harden, lift the mat
                                                  from the lap with a gentle stretching and pulling, carefully, so as
                                                  not to break any edges off the facets. Trim around the edge of the
                                                  lap with a sharp knife, flush it clean of rouge and pitch fragments,
                                                  dry it and coat the surfaces of the facets with smoking hot beeswax.
                                                  All of this takes about 15 minutes, less than half the time and fuss
                                                  needed for the conventional. lap. By working on a sheet of glass,
                                                  messiness is avoided, and the surplus pitch can be recovered and
                                                  returned to the pot.
                                                  The theory of the graduated spacing (see diagram) is that an oblate
                                                  spheroid can be brought spherical by concentrating the strokes on the
                                                  diameter of greatest facet density, and that a spherical mirror can
                                                  be similarly parabolized. There would be no walking around the
                                                  barrel, but necessity for rotating the mirror and pressing frequently
                                                  to maintain a surface of revolution on the lap. But therein lies the
                                                  rub; a similar surface must be present on the mirror. And so, because
                                                  of the ever-present danger of an astigmatic surface resulting from
                                                  this method, the above theoretical practice is not recommended. Used
                                                  in the normal way, the graduated spacing permits a wider range of
                                                  stroke than is possible on the channeled lap; thus "zones" are almost
                                                  entirely eliminated, and the spherical and paraboloidal figures are
                                                  more easily obtained.
                                                  THE PITCH LAP
                                                  57

                                                  Making Contact. Before polishing can begin, the newly made lap must
                                                  be immersed in hot water for three or four minutes (five minutes or
                                                  more for the channeled lap) in order that the pitch may be slightly
                                                  softened. In the meantime, the barrel top should be fitted with three
                                                  wooden cleats (Fig. 27) ; and a clean sheet of paper, with cutouts to
                                                  fit over the cleats, might be placed on top. Put a spoonful or two of
                                                  rouge or other polishing agent in a clean jar, add water and stir.
                                                  Use a small paint brush to apply the mixture (a creamy application
                                                  for the initial charge) to the face of the mirror. (Watch out for
                                                  loose bristles.) Remove the lap from the hot water and wedge it
                                                  firmly between the cleats. Immediately place the charged mirror on
                                                  top and work it back and forth with pressure for a few seconds in
                                                  order to embed the polishing compound in the waxed surface of the
                                                  lap. Then, with the mirror centered on the lap, place a weight of
                                                  about 20 pounds on top of it, and allow it to press for about 15
                                                  minutes, or until all of the heat has gone out of the tool. This
                                                  process is known as hot-pressing, and should precede each day's
                                                  polishing operation, the purpose being to bring the surfaces of lap
                                                  and mirror into contact at every point.
                                                  Incongruous results in figuring sometimes occur, traceable to a
                                                  temporary deformation or bending of the mirror induced by unequal
                                                  loading during the pressing period. The deformation is impressed into
                                                  the lap, and therein lies a source of unforeseen trouble. To avoid
                                                  this and insure equal distribution of the weights, they should rest
                                                  on a 6" square or round board which has three pegs, such as rubber-
                                                  head tacks, driven into it 120̊ apart in a centrally inscribed circle
                                                  of 21/g" radius. The pegs, in turn, rest on the mirror.
                                                  In putting the lap away for the night, the free polishing compound
                                                  should be flushed off, and a cover placed over the lap. Nothing, not
                                                  even the finger tips (save perhaps a clean sheet of paper intended as
                                                  a cover), should be allowed to come into contact with the surface of
                                                  the lap.
                                                  I'm sorry I cannot give you the images in the fig.

                                                  Talquence
                                                • Ken Hunter
                                                  ... Is it just me or are we beginning to accept that you will have to rechannel a lap numerous times during the polishing of a small optic? I ve used these lap
                                                  Message 24 of 27 , Dec 14, 2005
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                                                    --- In atm_free@yahoogroups.com, "Mitchell" <Funnybone101@c...>
                                                    wrote:
                                                    >
                                                    > --- In atm_free@yahoogroups.com, "Jerry" <wa4guu@b...> wrote:
                                                    > >
                                                    > > Some people use those molds. I don't think you can "re-channel"
                                                    > with the
                                                    > > mold,

                                                    Is it just me or are we beginning to accept that you will have to
                                                    rechannel a lap numerous times during the polishing of a small optic?

                                                    I've used these lap molds over the years and have made channels the
                                                    old fashioned way too... I can't accept that the pitch will flow so
                                                    much that the lap has to be trimmed every time you have a polishing
                                                    session. I've made many, many mirrors over the past 40 years and
                                                    have polished several 6 inch diameter mirrors on the same lap
                                                    without trimming at all. I've done this numerous times.

                                                    I posted a couple years back about the amount of flow the lap needs
                                                    to keep up with the changing surface of the glass. Any more flow
                                                    than that and the optician is just trying to catch up with the lap's
                                                    ever changing surface which extends the polishing time, causes zones
                                                    and necessitates retrimming and remaking of the lap. All this is
                                                    totally unnecessary to polish an optic.

                                                    Slightly softer pitch is desirable during the figuring stage but
                                                    polishing to a spherical shape can best be done with harder pitch as
                                                    long as the lap remains well pressed between sessions.

                                                    Ken Hunter
                                                  • Jerry
                                                    I accept that some people will. If Mitchell doesn t harden up his pitch or get a new supply he will have to re-trim several times. If I give advice on
                                                    Message 25 of 27 , Dec 14, 2005
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                                                      I accept that some people will.

                                                       

                                                      If Mitchell doesn’t harden up his pitch  or get a new supply he will have to re-trim several times. 

                                                       

                                                      If I give advice on polishing I always start out by stating my belief that the pitch hardness and working at a proper temperature are very important. That being said I know that only experience will convince someone. And when they become convinced they still don’t know how to control the hardness.

                                                       

                                                      I could sure polish out one 6 inch without trimming. I haven’t tried several because I never had several at one time. My experience has been that softer pitch polishes faster but does make a relatively ugly shape. Our difference of opinion there might be in the degree of softness/hardness. If I had to re-trim every half hour I would make a new harder lap.  I would consider that pitch “too soft to use”, so it wouldn’t even rate to be called soft pitch.

                                                       

                                                      I am not pro or anti mold.  There are so many ways to make a lap.  I don’t claim my way to be best or easiest.  It is just that “I” find no difficulty making it my way, and I like the results.  I don’t think there is anything wrong with the soldering Iron technique of channeling or a mold or a wood dowel, as long as you take care not to contaminate the lap.  But really… on a small mirror I just can’t see the expense when that money could go to some good pitch.

                                                       

                                                      I was hoping Gordon had advised Mitchell on his pitch.  But maybe the temperature was different than when Mitchell is working his glass. An ATM in person can be much better help than 50 ATMs on line.

                                                       

                                                      Jerry

                                                       

                                                       

                                                       

                                                       

                                                      -----Original Message-----
                                                      From: On Behalf Of
                                                      Ken Hunter
                                                       


                                                      Is it just me or are we beginning to accept that you will have to
                                                      rechannel a lap numerous times during the polishing of a small optic?

                                                      I've used these lap molds over the years and have made channels the
                                                      old fashioned way too... I can't accept that the pitch will flow so
                                                      much that the lap has to be trimmed every time you have a polishing
                                                      session. I've made many, many mirrors over the past 40 years and
                                                      have polished several 6 inch diameter mirrors on the same lap
                                                      without trimming at all. I've done this numerous times.

                                                      I posted a couple years back about the amount of flow the lap needs
                                                      to keep up with the changing surface of the glass. Any more flow
                                                      than that and the optician is just trying to catch up with the lap's
                                                      ever changing surface which extends the polishing time, causes zones
                                                      and necessitates retrimming and remaking of the lap. All this is
                                                      totally unnecessary to polish an optic.

                                                      Slightly softer pitch is desirable during the figuring stage but
                                                      polishing to a spherical shape can best be done with harder pitch as
                                                      long as the lap remains well pressed between sessions.

                                                      Ken Hunter






                                                    • Richard Schwartz
                                                      The razor blade is really the best way to channel. There is no molten pitch to accidentally spill into the carpets in your house, and the crumpled pitch that
                                                      Message 26 of 27 , Dec 15, 2005
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                                                        Message
                                                        The razor blade is really the best way to channel.  There is no molten pitch to accidentally spill into the carpets in your house, and the crumpled pitch that you cut out with the razor is easy to clean up.  The razor has other uses:
                                                         
                                                        1. Use it in your foucault tester.
                                                         
                                                        2. Use it to channel and maintain your pitch lap.
                                                         
                                                        3. Use it to cut your wrist arteries when you want to stop making mirrors.
                                                         
                                                        -----Original Message-----
                                                        From: atm_free@yahoogroups.com [mailto:atm_free@yahoogroups.com] On Behalf Of Jerry
                                                        Sent: Tuesday, December 13, 2005 8:08 PM
                                                        To: atm_free@yahoogroups.com
                                                        Subject: RE: [atm_free] Re: Two new photos

                                                        Some people use those molds. I don’t think you can “re-channel” with the mold, so you would have to trim the lap anyway.  The facet dimensions will change as you work and press.  So I think you can only use the mold when you make the lap.

                                                         

                                                        I used a similar thing 30 years ago.  It was a hard rubber grid.  I used it once.  I didn’t like it. I channel and trim with a single edge razor.  I’m good at it so see no reason to do it any other way. It gives me more control over depth of channel and size of facet. I’ll bet I am one of only a few still doing it with a razor blade.

                                                         

                                                        I would say wait until you are making a larger mirror, say 10 or 12 inches or larger. If there were an advantage to using it you would not realize it on a 6 inch lap. Even a 10 inch does not require much work to cut channels.

                                                         

                                                        Spend the money on pitch.  You can really make a lap with that.

                                                         

                                                         

                                                        -----Original Message-----
                                                        From:  Mitchell
                                                         
                                                        yup I brought my lap. He confirmed all our discussion, it's Acculap.
                                                        Speaking of my lap, since it appears i will have to do atleast
                                                        another 7 hours, what about a lap mold? like the ones sold here...

                                                        http://www.pitchlaps.com/

                                                         

                                                        Yep! And he recommended more pressure too.

                                                         

                                                        the stroke i was refering to was basically 1/3 coc, with no side to
                                                        side movement that i was doing before, someone else here also
                                                        suggested it.

                                                        Mitch

                                                         

                                                        After you do a couple of hours of polishing take another picture.  And one of your new lap also. 

                                                         

                                                        Jerry

                                                         


                                                      • Jerry
                                                        And! .. advanced ATM be the ladies rave when you use em And your finished mirror to shave. Burma Shave! Jerry ... From: Richard Schwartz The razor blade is
                                                        Message 27 of 27 , Dec 15, 2005
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                                                          Message

                                                          And! …… advanced ATM

                                                          be the ladies rave

                                                          when you use em

                                                          And your finished mirror

                                                          to shave.

                                                           

                                                          Burma Shave!

                                                           

                                                           

                                                           

                                                          Jerry

                                                           

                                                           

                                                          -----Original Message-----
                                                          From:
                                                          Richard Schwartz
                                                           

                                                          The razor blade is really the best way to channel.  There is no molten pitch to accidentally spill into the carpets in your house, and the crumpled pitch that you cut out with the razor is easy to clean up.  The razor has other uses:

                                                           

                                                          1. Use it in your foucault tester.

                                                           

                                                          2. Use it to channel and maintain your pitch lap.

                                                           

                                                          3. Use it to cut your wrist arteries when you want to stop making mirrors.

                                                           

                                                          -----Original Message-----
                                                          From:
                                                          Jerry

                                                          Some people use those molds. I don’t think you can “re-channel” with the mold, so you would have to trim the lap anyway.  The facet dimensions will change as you work and press.  So I think you can only use the mold when you make the lap.

                                                           

                                                          I used a similar thing 30 years ago.  It was a hard rubber grid.  I used it once.  I didn’t like it. I channel and trim with a single edge razor.  I’m good at it so see no reason to do it any other way. It gives me more control over depth of channel and size of facet. I’ll bet I am one of only a few still doing it with a razor blade.

                                                           

                                                          I would say wait until you are making a larger mirror, say 10 or 12 inches or larger. If there were an advantage to using it you would not realize it on a 6 inch lap. Even a 10 inch does not require much work to cut channels.

                                                           

                                                          Spend the money on pitch.  You can really make a lap with that.

                                                           

                                                           

                                                          -----Original Message-----
                                                          From:  Mitchell
                                                           
                                                          yup I brought my lap. He confirmed all our discussion, it's Acculap.
                                                          Speaking of my lap, since it appears i will have to do atleast
                                                          another 7 hours, what about a lap mold? like the ones sold here...

                                                          http://www.pitchlaps.com/

                                                           

                                                          Yep! And he recommended more pressure too.

                                                           

                                                          the stroke i was refering to was basically 1/3 coc, with no side to
                                                          side movement that i was doing before, someone else here also
                                                          suggested it.

                                                          Mitch

                                                           

                                                          After you do a couple of hours of polishing take another picture.  And one of your new lap also. 

                                                           

                                                          Jerry

                                                           

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