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Re: Alignment on a rotary table

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  • jjfear
    Ed, I ve never tried to do what you are doing, but suspect as you do that the problem is the manual layout. In my experience, it s better to let the machine
    Message 1 of 18 , Apr 7, 2002
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      Ed,
      I've never tried to do what you are doing, but suspect as you do that
      the problem is the manual layout. In my experience, it's better to
      let the machine do the measuring and layout for you (I'm not talking
      about the dials.)

      There are many edge finders available and cheap. I like the one that
      is .200 in size on the working end. When it touches the work and
      stops wobbling, I just have to subtract .100 to locate the exact edge
      of the work. Using a dial indicator I can move the work exactly under
      the spindle center, without so much as making a measurement or mark.
      On square stock, I would then use the other axis to locate the 90%
      edge, subtract .001 and move it to the exact distance I need (say to
      drill a hole) and I have located the center of the hole, again without
      any measurement. Then I center drill, drill and tap without moving the
      work, or having to put a center in the spindle to try find a punch mark.

      Since you are working in the round with a rotary table, locate one
      side as above. Rotate the work 45% and see if the edge measures
      exactly the same, and so on at 90 % and 135%. If it is not the same
      at any of these other positions, then the table or work is not centered.

      Move it the direction its off by 1/2 and try it again. Should get it
      dead on within 2-3 tries.

      This takes longer to explain than to do. Once you have used this
      method a few times, it really becomes easy and much more accurate than
      any measurement with a ruler, square, etc. For only the crudest work,
      do I measure and mark and in woodworking.
      HTH



      --- In GrizHFMinimill@y..., "rabeet00" <rabeet00@y...> wrote:
      > Aligning the work to the spindle seems a lot easier than aligning it
      > to the table, so far as I can tell.
      >
      > What would make this simple is a self-centering chuck mounted on a
      > taper dropped into the hole in the RT. I think. ;)
      >
      > I am going to try one of those center finder widgets next.
      >
      > Ed
      >
      > <snip>
      > > For a complete bullnose, you will have a semicircle just tangent to
      > > the two edges of the work, and at that tangency condition the point
      > > of contact has maximum rate of change. So we need to find a way to
      > > get the work mounted "perfectly" to some extremely fine tolerance!
      > > What do people do to get that right?
      > > Bob Wilson
    • Harvey White
      ... Not that I ve solved this problem but theoretically, still... 1: centering the table first. I have one of those centering gadgets, the one with the dial
      Message 2 of 18 , Apr 7, 2002
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        On Sun, 07 Apr 2002 15:06:38 -0000, you wrote:

        >Aligning the work to the spindle seems a lot easier than aligning it
        >to the table, so far as I can tell.
        >
        >What would make this simple is a self-centering chuck mounted on a
        >taper dropped into the hole in the RT. I think. ;)
        >
        >I am going to try one of those center finder widgets next.
        >
        >Ed

        Not that I've solved this problem but theoretically, still...

        1: centering the table first. I have one of those centering gadgets,
        the one with the dial and variable form feelers. Enco has one on sale
        now, and penn tools had one on sale, and you still might be able to
        get for the 79 dollar price (79.99).

        That allows you to center the table well enough. Which, on further
        thought, buys you nothing.

        However, centering the work is a bit more dicey. You can use a spud,
        which is a cylinder of metal with a blunt point on the work itself,
        The work would be accurately centered, then drilled for the spud
        (center drill is OK), then remounted on the table. The spud is
        lowered, and the workpiece is forced into alignment... Works, but
        leaves you with a hole in the center.

        Another possibility is that you take the same centering indicator, and
        set it for a larger arc. If you have the tangent line for the circle
        drawn, you find the center of that line with the centering indicator.
        Not sure how well that would work, but my mental picture has the
        feeler swinging in free air, then contacting the work on both sides.
        Tangent line might not be important, since you're balancing the
        readings, and you'll find the center regardless.

        Another possibility. Draw a number of lines parallel to the short
        axis of the bar, center by eye, then start to mill. As you do, tweak
        the rotary table x or y a bit to get the tangent lines exact, as
        needed. That sounds like it would work better.


        Begs the question, though..

        Harvey


        >
        ><snip>
        >> For a complete bullnose, you will have a semicircle just tangent to
        >> the two edges of the work, and at that tangency condition the point
        >> of contact has maximum rate of change. So we need to find a way to
        >> get the work mounted "perfectly" to some extremely fine tolerance!
        >> What do people do to get that right?
        >> Bob Wilson
        >
        >
        >
        >
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        >GrizHFMinimill-unsubscribe@yahoogroups.com
        >
        >
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        >
      • rabeet00
        Ah, that makes perfect sense. Thanks, I believe you have given me a good direction to go in. Ed ... that ...
        Message 3 of 18 , Apr 7, 2002
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          Ah, that makes perfect sense.

          Thanks, I believe you have given me a good direction to go in.

          Ed

          > Ed,
          > I've never tried to do what you are doing, but suspect as you do
          that
          > the problem is the manual layout. In my experience, it's better to
          > let the machine do the measuring and layout for you (I'm not talking
          > about the dials.)
          >
          <snip good advice>
        • Barry Young
          Hi Ed: When putting a radius on the end of a bar, it takes very little error to end up with quite a noticeable mismatch. This is called Cosine error I think.
          Message 4 of 18 , Apr 8, 2002
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            Hi Ed:

            When putting a radius on the end of a bar, it takes
            very little error to end up with quite a noticeable
            mismatch. This is called Cosine error I think.

            The solution is fairly simple as these things go. To
            get the thing to make "perfect radii on the ends of
            bars you will almost certainly have to use a test
            indicator. Aligning the center of a bar by eye is a
            hit and miss operation no matter how careful you are.
            On my Minimill, I use an Indicol indicator holder with
            a wooden block drilled to accept the mounting screw.
            The block steps the thing down small enough to fit
            over the chuck body on the minimill. Another option
            would be to make a holding bar for the indicator, I am
            sure the ways to hold one have not been exhausted by
            mankind.

            Once mounted, use the indicator to "dial in" the
            central hole of the rotab. Lining up centers will not
            be precise enough. Lock down the X and Y table
            movements. Then when you have the bar mounted where
            you want it on the rotab, use the downfeed to move the
            indicator probe down along the side of the bar until
            you reach the highest spot. Wiggle the chuck a bit to
            make sure you are on the highest point along the bar
            as well. Lift the head and repeat on the other side of
            the bar. Adjust the position of the bar on the rotab
            until you can see no difference from one side to the
            other. You now have the rod directly under the
            spindle. Not the X handwheel reading so that you can
            return to the center of the table when you want to.
            With the indicator still on the side of the bar, move
            the table in X to determine when the rod is parallel
            with X. Adjust by turning the rotab table. Now the bar
            is centered and parallel. Your radius cut will now be
            equal on both sides.

            Good luck

            Barry Young








            --- rabeet00 <rabeet00@...> wrote:
            > So I have been using my recently obtained rotary
            > table more and more,
            > but I still have yet to have it quite figured out. I
            > bought the 6"
            > horizontal that LMS sells. Seems quite nice to me.
            >
            > Here is an example of one problem I am having:
            >
            > Hunk of 3/4 x 1/2 T6 bar stock. Want to make a half
            > round bull nose
            > on each end.
            >
            > Scribe a line down the center of the bar. Punch
            > marks 3/8 from each
            > end. I use an Inca rule and square for this kind of
            > layout work.
            >
            > Mount the rotary table on the mill. Align the RT
            > with the spindle
            > using a live center in the RT and a dead center in
            > the spindle. Lock
            > X and Y axis.
            >
            > Clamp the work on the table, aligning the punch
            > marks with a dead
            > center in the spindle. I do this sort of work with
            > high power reading
            > glasses on, so I am fairly confident it is close.
            >
            > Unlock the Y axis, and back off enough to start
            > milling the end. I
            > used a 7/16 end mill, but I assume that is
            > irrelevant.
            >
            > Trouble is, I always appear to be not quite on
            > center. I reach the
            > edge on one side before the other.
            >
            > I assume my problem here is the punch mark is not
            > centered on the
            > work. Does this sound like a likely cause or am I
            > missing something
            > in my technique?
            >
            > The funny thing is, I slapped a bit of bar on the RT
            > the other day,
            > aligning the work just by eye over the hole in the
            > center of the RT.
            > Just wanted to practice. It came out within about
            > .005. Sheesh!
            >
            > Thanks,
            >
            > Ed
            >
            >
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          • rabeet00
            Barry, That makes sense. I do have dial and test indicators, but the only spindle mount I have are the inexpensive sort that clamps around the spindle, plus
            Message 5 of 18 , Apr 8, 2002
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              Barry,

              That makes sense. I do have dial and test indicators, but the only
              spindle mount I have are the inexpensive sort that clamps around the
              spindle, plus the ones that came with the 0-30-0. I will have to get
              one of those Indicol widgets.

              Since I posted, I came to the conclusion that asthetic curves such as
              a bull nose are a lot easier if I made the radius a bit larger. This
              hides the point where the curve meets the side of the bar.

              I also started trying to use indicators to accomplish better results
              when I actually want it to be as perfect as possible. Your method
              sounds like it will work for me.

              One very odd thing I noticed, though. I tried aligning the RT three
              ways:

              1. as before, using a live center in the RT and a dead center in the
              spindle.

              2. using an indicator against the slope of the live center.

              3. using an indicator in the hole in the RT.

              I also tested both centers and the spindle for run out, so I knew
              where I sat there.

              What threw me as I messed around with this was that #1 was very
              different from #2 and 3. And I mean by a good .05 inches. Everything
              tested quite well for runout, so I have no idea where that error is
              coming from. The "manual" method of using the two centers should not
              have been off by more than a few thou.

              Ed

              > Hi Ed:
              >
              > When putting a radius on the end of a bar, it takes
              > very little error to end up with quite a noticeable
              > mismatch. This is called Cosine error I think.
              >
              > The solution is fairly simple as these things go. To
              > get the thing to make "perfect radii on the ends of
              > bars you will almost certainly have to use a test
              > indicator. Aligning the center of a bar by eye is a
              > hit and miss operation no matter how careful you are.
              > On my Minimill, I use an Indicol indicator holder with
              > a wooden block drilled to accept the mounting screw.
              > The block steps the thing down small enough to fit
              > over the chuck body on the minimill. Another option
              > would be to make a holding bar for the indicator, I am
              > sure the ways to hold one have not been exhausted by
              > mankind.
              >
              <snip good advice>
            • rabeet00
              Here is an example of something that uses both cosmetic rounds and one that I wanted to be pretty much spot on. Made this over this past weekend for a friend.
              Message 6 of 18 , Apr 9, 2002
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                Here is an example of something that uses both cosmetic rounds and
                one that I wanted to be pretty much spot on. Made this over this past
                weekend for a friend. It is a handle for lifting a motorcycle onto
                its center stand. The anodized blue part is not made by me.

                http://www.nvxd.com/brackets/apebar_2.jpg

                http://www.nvxd.com/brackets/apebar_3.jpg
              • Barry Young
                Looks can be very deceiving when aligning two tapers. When I first got my 9X20, I tossed dead centers in the spindle and tailstock and was very pleased that
                Message 7 of 18 , Apr 9, 2002
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                  Looks can be very deceiving when aligning two tapers.
                  When I first got my 9X20, I tossed dead centers in the
                  spindle and tailstock and was very pleased that they
                  lined up perfectly. I was able to turn a longish shaft
                  to witin .001 BEFORE I adjusted the tailstock setover
                  to make it within limits I was able to measure. It
                  wasn't until several months later when I was making
                  something that needed to be as perfect as I could make
                  it that I swept the top of a bar I had turned. I was
                  amazed that there was .010 difference in height from
                  spindle to tailstock even though the bar was the
                  desired diameter the entire length. Duh!!!! Although
                  the centers were on the spindle axis along the X axis,
                  the tailstock was .010 higher than the spindle. After
                  surface grinding the base of the taistock body,
                  everything is now in line. I just could not believe I
                  didn't check it. I guess I figured that if the
                  diameter of the test bar was good, I must be lined up.
                  The funny thing is that I could not see the .010 error
                  by looking at the points of the centers. I now use an
                  indicator only for aligning anything.

                  Barry Young
                  --- rabeet00 <rabeet00@...> wrote:
                  > Barry,
                  >
                  > That makes sense. I do have dial and test
                  > indicators, but the only
                  > spindle mount I have are the inexpensive sort that
                  > clamps around the
                  > spindle, plus the ones that came with the 0-30-0. I
                  > will have to get
                  > one of those Indicol widgets.
                  >
                  > Since I posted, I came to the conclusion that
                  > asthetic curves such as
                  > a bull nose are a lot easier if I made the radius a
                  > bit larger. This
                  > hides the point where the curve meets the side of
                  > the bar.
                  >
                  > I also started trying to use indicators to
                  > accomplish better results
                  > when I actually want it to be as perfect as
                  > possible. Your method
                  > sounds like it will work for me.
                  >
                  > One very odd thing I noticed, though. I tried
                  > aligning the RT three
                  > ways:
                  >
                  > 1. as before, using a live center in the RT and a
                  > dead center in the
                  > spindle.
                  >
                  > 2. using an indicator against the slope of the live
                  > center.
                  >
                  > 3. using an indicator in the hole in the RT.
                  >
                  > I also tested both centers and the spindle for run
                  > out, so I knew
                  > where I sat there.
                  >
                  > What threw me as I messed around with this was that
                  > #1 was very
                  > different from #2 and 3. And I mean by a good .05
                  > inches. Everything
                  > tested quite well for runout, so I have no idea
                  > where that error is
                  > coming from. The "manual" method of using the two
                  > centers should not
                  > have been off by more than a few thou.
                  >
                  > Ed


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                • Barry Young
                  Nice work, and great photography Barry Young ... __________________________________________________ Do You Yahoo!? Yahoo! Tax Center - online filing with
                  Message 8 of 18 , Apr 9, 2002
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                    Nice work, and great photography

                    Barry Young


                    --- rabeet00 <rabeet00@...> wrote:
                    > Here is an example of something that uses both
                    > cosmetic rounds and
                    > one that I wanted to be pretty much spot on. Made
                    > this over this past
                    > weekend for a friend. It is a handle for lifting a
                    > motorcycle onto
                    > its center stand. The anodized blue part is not made
                    > by me.
                    >
                    > http://www.nvxd.com/brackets/apebar_2.jpg
                    >
                    > http://www.nvxd.com/brackets/apebar_3.jpg
                    >
                    >
                    >
                    >
                    > ------------------------ Yahoo! Groups Sponsor
                    >
                    > To unsubscribe from this group, send an email to:
                    > GrizHFMinimill-unsubscribe@yahoogroups.com
                    >
                    >
                    >
                    > Your use of Yahoo! Groups is subject to
                    > http://docs.yahoo.com/info/terms/
                    >
                    >


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                  • catboat15@aol.com
                    In a message dated 4/8/02 6:44:33 PM Pacific Daylight Time, ... I know it is not a machine tool, but a file and filing buttons does this job just fine and
                    Message 9 of 18 , Apr 10, 2002
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                      In a message dated 4/8/02 6:44:33 PM Pacific Daylight Time, barryjyoung@... writes:


                      When putting a radius on the end of a bar, it takes
                      very little error to end up with quite a noticeable
                      mismatch.


                      I know it is not a machine tool, but a file and filing buttons does this job just fine and usually faster than making a set up on the mill.
                      John Meacham
                      High Desert of California, Palmdale, Littlerock.
                    • Derek
                      ... Someone else suggested that a few days ago. Seems a good idea to me. Derek __________________________________________________ Do You Yahoo!? Yahoo! Tax
                      Message 10 of 18 , Apr 10, 2002
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                        > I know it is not a machine tool, but a file and filing buttons does
                        > this job
                        > just fine and usually faster than making a set up on the mill.


                        Someone else suggested that a few days ago.
                        Seems a good idea to me.
                        Derek






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                      • rabeet00
                        What is a filing button? Ed ... this job
                        Message 11 of 18 , Apr 11, 2002
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                          What is a filing button?

                          Ed

                          > > When putting a radius on the end of a bar, it takes
                          > > very little error to end up with quite a noticeable
                          > > mismatch.
                          >
                          > I know it is not a machine tool, but a file and filing buttons does
                          this job
                          > just fine and usually faster than making a set up on the mill.
                          > John Meacham
                          > High Desert of California, Palmdale, Littlerock.
                        • rabeet00
                          Thing is I am trying to learn the principle here, not the best way to make a bull nose. I need to be able to do precision RT work for making clamps and other
                          Message 12 of 18 , Apr 11, 2002
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                            Thing is I am trying to learn the principle here, not the best way to
                            make a bull nose. I need to be able to do precision RT work for
                            making clamps and other fitted parts. I have made those by hand, but
                            it took some doing to get the fit well.

                            Still, I'd like to know what filing buttons are... ;)

                            Ed

                            > > I know it is not a machine tool, but a file and filing buttons
                            does
                            > > this job
                            > > just fine and usually faster than making a set up on the mill.
                            >
                            >
                            > Someone else suggested that a few days ago.
                            > Seems a good idea to me.
                            > Derek
                          • Barry Young
                            Hi John: Good point, just depends on the need for precision, and how many are being made. Barry Young ... __________________________________________________ Do
                            Message 13 of 18 , Apr 11, 2002
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                              Hi John:

                              Good point, just depends on the need for precision,
                              and how many are being made.

                              Barry Young


                              --- catboat15@... wrote:
                              > In a message dated 4/8/02 6:44:33 PM Pacific
                              > Daylight Time,
                              > barryjyoung@... writes:
                              >
                              >
                              > > When putting a radius on the end of a bar, it
                              > takes
                              > > very little error to end up with quite a
                              > noticeable
                              > > mismatch.
                              >
                              > I know it is not a machine tool, but a file and
                              > filing buttons does this job
                              > just fine and usually faster than making a set up on
                              > the mill.
                              > John Meacham
                              > High Desert of California, Palmdale, Littlerock.
                              >


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