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Testing for accuracy?

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  • Armand
    On my Homier Mini-Lathe I tested the spindle runout with a dial indicator to see how accurate it is (I know this is only one test)....I just bought a HF
    Message 1 of 12 , Jan 22, 2004
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      On my Homier Mini-Lathe I tested the spindle runout with a dial
      indicator to see how accurate it is (I know this is only one
      test)....I just bought a HF Mini-Mill (I'm new to machining all
      together) and was wondering if I could use the same test to check the
      Mini-Mill? It seems kind of on the wobbly side and with a dial gauge
      the collet holder is over .001. Is this normal or is there a
      different way to test the machine? The gears and motor seem much
      noiser than the Lathe, but I'm assuming this is normal.

      Thanks. Sorry if this is a stupid question!
    • Dave Jarzyna
      Mount an end mill in the correct sized collet with enough full round shank below the collet to set your test indicator on. you need to test the concentricity
      Message 2 of 12 , Jan 23, 2004
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        Mount an end mill in the correct sized collet with enough full round
        shank below the collet to set your test indicator on. you need to
        test the concentricity of the collet bore - not the outside of the
        collet holder. Also- drill chucks are generally not extremly
        concentric unless purchased as very expensive precision accessory.
        Dave J

        " THE ONLY STUPID QUESTION IS THE ONE YOU DO NOT ASK.... "

        --- In GrizHFMinimill@yahoogroups.com, "Armand" <ducoar@y...> wrote:
        > On my Homier Mini-Lathe I tested the spindle runout with a dial
        > indicator to see how accurate it is (I know this is only one
        > test)....I just bought a HF Mini-Mill (I'm new to machining all
        > together) and was wondering if I could use the same test to check
        the
        > Mini-Mill? It seems kind of on the wobbly side and with a dial
        gauge
        > the collet holder is over .001. Is this normal or is there a
        > different way to test the machine? The gears and motor seem much
        > noiser than the Lathe, but I'm assuming this is normal.
        >
        > Thanks. Sorry if this is a stupid question!
      • ljack70117@adelphia.net
        This will give you the combined run out of the spindle and collet holder. With nothing in the spindle use a last word indicator and put the end in side the
        Message 3 of 12 , Jan 23, 2004
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          This will give you the combined run out of the spindle and collet
          holder. With nothing in the spindle use a last word indicator and put
          the end in side the spindle and turn the spindle. This will give you
          the run out. I think .001" is very good for these small Chinese
          machines.
          Thank you
          Larry Jackman


          On Friday, January 23, 2004, at 09:36 AM, Dave Jarzyna wrote:

          > Mount an end mill in the correct sized collet with enough full round
          > shank below the collet to set your test indicator on. you need to
          > test the concentricity of the collet bore - not the outside of the
          > collet holder. Also- drill chucks are generally not extremly
          > concentric unless purchased as very expensive precision accessory.
          > Dave J
          >
          > " THE ONLY STUPID QUESTION IS THE ONE YOU DO NOT ASK.... "
        • Armand
          Ok, testing the outside of the spindle I get between .001 -.0015 runout. On the inside bottom lip (R8 spindle) I get no more than .001 runout. On the inside
          Message 4 of 12 , Jan 23, 2004
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            Ok, testing the outside of the spindle I get between .001"-.0015"
            runout.

            On the inside bottom lip (R8 spindle) I get no more than .001" runout.

            On the inside upper (past where the R8 flares out) I get no more
            than .0005" runout

            Using the collet method it varies greatly, some collet/mills give
            me .001, some as much as .005!

            I guess since they say it's the same basic mech as the mini-lathe I
            was hoping to see the .0005 that I get measuring my mini-lathe.

            All in all I guess for the spindle measurements it seems pretty good,
            the collet/mill measurement are no so good though, but I think my
            test shows that variance is coming from the collet/mill.

            I have trammed the mill using the dial supported from the collet
            measuring equal spots on the bed, so I'm not sure if there are any
            other things I can/should to do tighten things up.

            Since I'm new to all of this I might be going about things the wrong
            way, I've use a dial indicator for all my tests so far. I've only
            milled a few blocks of 6061 and what got me wondering was that the
            ends of the 1"x2" blocks were not quite as flat as I hoped, but that
            was before I trammed the mill so I'm off to mill some more 6061 to
            check if things were better.

            Of course tomorrow is the 30 day mark from when I picked up the mill
            at my local HF store so I was just trying to figure out if I had a
            keeper or I should swap it. At this point I think it's a keeper.

            Feedback? or am I just crazy?

            Thanks for your help.



            --- In GrizHFMinimill@yahoogroups.com, ljack70117@a... wrote:
            > This will give you the combined run out of the spindle and collet
            > holder. With nothing in the spindle use a last word indicator and
            put
            > the end in side the spindle and turn the spindle. This will give
            you
            > the run out. I think .001" is very good for these small Chinese
            > machines.
            > Thank you
            > Larry Jackman
            >
            >
            > On Friday, January 23, 2004, at 09:36 AM, Dave Jarzyna wrote:
            >
            > > Mount an end mill in the correct sized collet with enough full
            round
            > > shank below the collet to set your test indicator on. you need to
            > > test the concentricity of the collet bore - not the outside of the
            > > collet holder. Also- drill chucks are generally not extremly
            > > concentric unless purchased as very expensive precision accessory.
            > > Dave J
            > >
            > > " THE ONLY STUPID QUESTION IS THE ONE YOU DO NOT ASK.... "
          • dds6263
            ... runout. ... good, ... wrong ... that ... mill ... to ... the ... accessory. ... Put a dial indicator up inside the spindle (on the tapered) surface to
            Message 5 of 12 , Jan 24, 2004
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              --- In GrizHFMinimill@yahoogroups.com, "Armand" <ducoar@y...> wrote:
              > Ok, testing the outside of the spindle I get between .001"-.0015"
              > runout.
              >
              > On the inside bottom lip (R8 spindle) I get no more than .001"
              runout.
              >
              > On the inside upper (past where the R8 flares out) I get no more
              > than .0005" runout
              >
              > Using the collet method it varies greatly, some collet/mills give
              > me .001, some as much as .005!
              >
              > I guess since they say it's the same basic mech as the mini-lathe I
              > was hoping to see the .0005 that I get measuring my mini-lathe.
              >
              > All in all I guess for the spindle measurements it seems pretty
              good,
              > the collet/mill measurement are no so good though, but I think my
              > test shows that variance is coming from the collet/mill.
              >
              > I have trammed the mill using the dial supported from the collet
              > measuring equal spots on the bed, so I'm not sure if there are any
              > other things I can/should to do tighten things up.
              >
              > Since I'm new to all of this I might be going about things the
              wrong
              > way, I've use a dial indicator for all my tests so far. I've only
              > milled a few blocks of 6061 and what got me wondering was that the
              > ends of the 1"x2" blocks were not quite as flat as I hoped, but
              that
              > was before I trammed the mill so I'm off to mill some more 6061 to
              > check if things were better.
              >
              > Of course tomorrow is the 30 day mark from when I picked up the
              mill
              > at my local HF store so I was just trying to figure out if I had a
              > keeper or I should swap it. At this point I think it's a keeper.
              >
              > Feedback? or am I just crazy?
              >
              > Thanks for your help.
              >
              >
              >
              > --- In GrizHFMinimill@yahoogroups.com, ljack70117@a... wrote:
              > > This will give you the combined run out of the spindle and collet
              > > holder. With nothing in the spindle use a last word indicator and
              > put
              > > the end in side the spindle and turn the spindle. This will give
              > you
              > > the run out. I think .001" is very good for these small Chinese
              > > machines.
              > > Thank you
              > > Larry Jackman
              > >
              > >
              > > On Friday, January 23, 2004, at 09:36 AM, Dave Jarzyna wrote:
              > >
              > > > Mount an end mill in the correct sized collet with enough full
              > round
              > > > shank below the collet to set your test indicator on. you need
              to
              > > > test the concentricity of the collet bore - not the outside of
              the
              > > > collet holder. Also- drill chucks are generally not extremly
              > > > concentric unless purchased as very expensive precision
              accessory.
              > > > Dave J
              > > >
              > > > " THE ONLY STUPID QUESTION IS THE ONE YOU DO NOT ASK.... "



              Put a dial indicator up inside the spindle (on the tapered) surface
              to determine the circumferential run out, mine was pretty good.
              However that does not determine the total run out of the BASE axis of
              rotation nor the final run out at the cutting point of the tool. You
              must add in the errors of parallax - the additional error resulting
              from the outside and inside axes, not being parallel. It can be, the
              biggest portion of total error because the that part of the error is
              magnified the further away from you get from the spindle seat. The
              ball bearings which are pressed into the housing casting should run
              under a preload (zero clearances) and hence should establish a rigid
              well defined "BASE" axis of rotation. If the spindle, the collet and
              the tool all were perfect the resulting axis of rotation at the
              cutter would have zero run out. But those parts are never perfect.
              Each will add more error, the final total run out at the cutting
              point can be much more than we realize. Buy the most expensive
              collets you can afford - because most of the error is usually in that
              part. The spindle and the tool are usually pretty good.

              The circumferential run out of the inside my Homier spindle is
              about .00015"

              I purchased the most INexpensive collets money can buy and also a 8"
              length of precision ground .5000 diameter bar that is straight
              within .0001"

              When I measure the run out with that bar at 6" away from the spindle
              seat it measures .004". Almost all of which is attributed to the dam
              collet.

              When I put the drill chuck into the spindle and measure the run out
              at 6" away it measures a ridiculous .011" - You can see it wobble!

              And, these measurements are only averages. They change depending how
              much I tighten the draw bar and how far I insert the .5000 dia bar
              into the collett. I was really surprised at the amounts of, and non-
              repeatability of, the runouts. Maybe that is why you gotta pay a
              small fortune for a really accurate machine. Ya think?

              And as far as Tramming the Mini Mill about the spindle axis? That is
              for sure the single most important alignment to make, but there are
              other factors to consider. The spindle axis not only needs to be
              square to the bed, it also needs to be parallel with the "Z" axis
              (the column) in two planes or the cutter will move along the "X"
              or "Y" axis as it is is raised and lowered. The problem is that the
              Mini Mill is notorious for being shipped with the spindle axis not
              being parallel to the "Z" axis and there is no quick way to correct
              for it. For that matter there is no easy way to measure that amount
              of the error. For most of us we are never aware of that type of error
              because it only shows up when we make long cuts in the "Z" direction,
              like drilling a deep hole or attempting to finish the sides of a bar
              at 90 degrees to the "XY" surface. Usually the oversized diameter at
              the top of that deep hole, or the out of squareness of the sides are
              not noticable.
            • Armand
              Thanks for the into, this clears up things quite a bit. I will pick up some precision rod this week and give it a go with that. So much to learn, but it s a
              Message 6 of 12 , Jan 25, 2004
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                Thanks for the into, this clears up things quite a bit. I will pick
                up some precision rod this week and give it a go with that. So much
                to learn, but it's a ton of fun!

                --- In GrizHFMinimill@yahoogroups.com, "dds6263" <jpb62@j...> wrote:
                > Put a dial indicator up inside the spindle (on the tapered) surface
                > to determine the circumferential run out, mine was pretty good.
                > However that does not determine the total run out of the BASE axis
                of
                > rotation nor the final run out at the cutting point of the tool.
                You
                > must add in the errors of parallax - the additional error resulting
                > from the outside and inside axes, not being parallel. It can be,
                the
                > biggest portion of total error because the that part of the error
                is
                > magnified the further away from you get from the spindle seat. The
                > ball bearings which are pressed into the housing casting should run
                > under a preload (zero clearances) and hence should establish a
                rigid
                > well defined "BASE" axis of rotation. If the spindle, the collet
                and
                > the tool all were perfect the resulting axis of rotation at the
                > cutter would have zero run out. But those parts are never perfect.
                > Each will add more error, the final total run out at the cutting
                > point can be much more than we realize. Buy the most expensive
                > collets you can afford - because most of the error is usually in
                that
                > part. The spindle and the tool are usually pretty good.
                >
                > The circumferential run out of the inside my Homier spindle is
                > about .00015"
                >
                > I purchased the most INexpensive collets money can buy and also a
                8"
                > length of precision ground .5000 diameter bar that is straight
                > within .0001"
                >
                > When I measure the run out with that bar at 6" away from the
                spindle
                > seat it measures .004". Almost all of which is attributed to the
                dam
                > collet.
                >
                > When I put the drill chuck into the spindle and measure the run out
                > at 6" away it measures a ridiculous .011" - You can see it wobble!
                >
                > And, these measurements are only averages. They change depending
                how
                > much I tighten the draw bar and how far I insert the .5000 dia bar
                > into the collett. I was really surprised at the amounts of, and non-
                > repeatability of, the runouts. Maybe that is why you gotta pay a
                > small fortune for a really accurate machine. Ya think?
                >
                > And as far as Tramming the Mini Mill about the spindle axis? That
                is
                > for sure the single most important alignment to make, but there
                are
                > other factors to consider. The spindle axis not only needs to be
                > square to the bed, it also needs to be parallel with the "Z" axis
                > (the column) in two planes or the cutter will move along the "X"
                > or "Y" axis as it is is raised and lowered. The problem is that the
                > Mini Mill is notorious for being shipped with the spindle axis not
                > being parallel to the "Z" axis and there is no quick way to correct
                > for it. For that matter there is no easy way to measure that amount
                > of the error. For most of us we are never aware of that type of
                error
                > because it only shows up when we make long cuts in the "Z"
                direction,
                > like drilling a deep hole or attempting to finish the sides of a
                bar
                > at 90 degrees to the "XY" surface. Usually the oversized diameter
                at
                > the top of that deep hole, or the out of squareness of the sides
                are
                > not noticable.
              • jjfear
                I don t have a name so I can t thank you personally for this post, but I really appreciated it. I always suspected tha there was some reason why Hardinge and
                Message 7 of 12 , Jan 25, 2004
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                  I don't have a name so I can't thank you personally for this post, but
                  I really appreciated it. I always suspected tha there was some reason
                  why Hardinge and Monarch lathes and Bridgeport mills cost a magnitude
                  of a hundred or thousand to our $300. lathes and $400. mills. I
                  figured there must be some reason. (sic)

                  In my experience, new machine owners generally have unrealistic
                  expectations of the accuracy of machinery, and discount the role
                  operator skill plays. This writer is included. When I bought a
                  Unimat 40 years ago, I was so dismayed at "its' lack of accuracy,"
                  that I sold it and didn't buy another lathe for 10 years. Woodworking
                  taught me that such accuracy does not really exist and is not
                  necessary.

                  I have posted several times on this list about what I consider a
                  pursuit of accuracy which is unrealistic, in these machines. In
                  manufacturing, where parts have to be interchangable, operating with
                  tolerances is a requirement, but in one-off operations, it's generally
                  not necessary. A cut and try fit is usually sufficient.

                  There is an Engineering Design Theory that goes something like this,
                  "Only as good as necessary to meet the minimum requirement." Beyond
                  that, the cost of any product is too high.

                  These machines are wonderfully designed and manufactured to meet the
                  minimum requirements of a home machinist's one-off projects. And it's
                  surprising how the machines accuracy improves with the machinist's
                  skill.

                  My advice is to worry less about runout than running the damn thing
                  and cutting metal. The last .001 comes off with emory paper anyhow.
                  Focus more on the accuracy of the machinist than on the accuracy of
                  the machine.

                  Sorry for the rant, but thanks for the post.

                  Jerry Fear
                  Denver, CO






                  --
                  a
                  > >
                  >
                  > Put a dial indicator up inside the spindle (on the tapered) surface
                  > to determine the circumferential run out, mine was pretty good.
                  > However that does not determine the total run out of the BASE axis
                  of
                  > rotation nor the final run out at the cutting point of the tool.
                  You
                  > must add in the errors of parallax - the additional error resulting
                  > from the outside and inside axes, not being parallel. It can be,
                  the
                  > biggest portion of total error because the that part of the error
                  is
                  > magnified the further away from you get from the spindle seat. The
                  > ball bearings which are pressed into the housing casting should run
                  > under a preload (zero clearances) and hence should establish a
                  rigid
                  > well defined "BASE" axis of rotation. If the spindle, the collet
                  and
                  > the tool all were perfect the resulting axis of rotation at the
                  > cutter would have zero run out. But those parts are never perfect.
                  > Each will add more error, the final total run out at the cutting
                  > point can be much more than we realize. Buy the most expensive
                  > collets you can afford - because most of the error is usually in
                  that
                  > part. The spindle and the tool are usually pretty good.
                  >
                  > The circumferential run out of the inside my Homier spindle is
                  > about .00015"
                  >
                  > I purchased the most INexpensive collets money can buy and also a
                  8"
                  > length of precision ground .5000 diameter bar that is straight
                  > within .0001"
                  >
                  > When I measure the run out with that bar at 6" away from the
                  spindle
                  > seat it measures .004". Almost all of which is attributed to the
                  dam
                  > collet.
                  >
                  > When I put the drill chuck into the spindle and measure the run out
                  > at 6" away it measures a ridiculous .011" - You can see it wobble!
                  >
                  > And, these measurements are only averages. They change depending
                  how
                  > much I tighten the draw bar and how far I insert the .5000 dia bar
                  > into the collett. I was really surprised at the amounts of, and non-
                  > repeatability of, the runouts. Maybe that is why you gotta pay a
                  > small fortune for a really accurate machine. Ya think?
                  >
                  > And as far as Tramming the Mini Mill about the spindle axis? That
                  is
                  > for sure the single most important alignment to make, but there
                  are
                  > other factors to consider. The spindle axis not only needs to be
                  > square to the bed, it also needs to be parallel with the "Z" axis
                  > (the column) in two planes or the cutter will move along the "X"
                  > or "Y" axis as it is is raised and lowered. The problem is that the
                  > Mini Mill is notorious for being shipped with the spindle axis not
                  > being parallel to the "Z" axis and there is no quick way to correct
                  > for it. For that matter there is no easy way to measure that amount
                  > of the error. For most of us we are never aware of that type of
                  error
                  > because it only shows up when we make long cuts in the "Z"
                  direction,
                  > like drilling a deep hole or attempting to finish the sides of a
                  bar
                  > at 90 degrees to the "XY" surface. Usually the oversized diameter
                  at
                  > the top of that deep hole, or the out of squareness of the sides
                  are
                  > not noticable.
                • g_f_bravo_g
                  in this web, you can read a about adjusting mills http://sherline.com/2000inst.htm German
                  Message 8 of 12 , Jan 26, 2004
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                    in this web, you can read a about adjusting mills

                    http://sherline.com/2000inst.htm

                    German
                  • Jim Izzolo
                    Excellent post Jerry. It made a lot of sense to me. Jim I jjfear wrote: I don t have a name so I can t thank you personally for this
                    Message 9 of 12 , Jan 26, 2004
                    • 0 Attachment
                      Excellent post Jerry.  It made a lot of sense to me. 
                      Jim I 

                      jjfear <jjfear@...> wrote:
                      I don't have a name so I can't thank you personally for this post, but
                      I really appreciated it.  I always suspected tha there was some reason
                      why Hardinge and Monarch lathes and Bridgeport mills cost a magnitude
                      of a hundred or thousand to our $300. lathes and $400. mills.  I
                      figured there must be some reason. (sic)

                      In my experience, new machine owners generally have unrealistic
                      expectations of the accuracy of machinery, and discount the role
                      operator skill plays.  This writer is included.  When I bought a
                      Unimat 40 years ago, I was so dismayed at "its' lack of accuracy,"
                      that I sold it and didn't buy another lathe for 10 years.  Woodworking
                      taught me that such accuracy does not really exist and is not
                      necessary.

                      I have posted several times on this list about what I consider a
                      pursuit of accuracy which is unrealistic, in these machines.  In
                      manufacturing, where parts have to be interchangable, operating with
                      tolerances is a requirement, but in one-off operations, it's generally
                      not necessary.  A cut and try fit is usually sufficient.

                      There is an Engineering Design Theory that goes something like this,
                      "Only as good as necessary to meet the minimum requirement."  Beyond
                      that, the cost of any product is too high.

                      These machines are wonderfully designed and manufactured to meet the
                      minimum requirements of a home machinist's one-off projects.  And it's
                      surprising how the machines accuracy improves with the machinist's
                      skill.

                      My advice is to worry less about runout than running the damn thing
                      and cutting metal.  The last .001 comes off with emory paper anyhow.
                      Focus more on the accuracy of the machinist than on the accuracy of
                      the machine.

                      Sorry for the rant, but thanks for the post.

                      Jerry Fear
                      Denver, CO






                      --
                      a
                      > >
                      >
                      > Put a dial indicator up inside the spindle (on the tapered) surface
                      > to determine the circumferential run out, mine was pretty good.
                      > However that does not determine the total run out of the BASE axis
                      of
                      > rotation nor the final run out at the cutting point of the tool.
                      You
                      > must add in the errors of parallax - the additional error resulting
                      > from the outside and inside axes, not being parallel. It can be,
                      the
                      > biggest portion of total error because the that part of the error
                      is
                      > magnified the further away from you get from the spindle seat. The
                      > ball bearings which are pressed into the housing casting should run
                      > under a preload (zero clearances) and hence should establish a
                      rigid
                      > well defined "BASE" axis of rotation. If the spindle, the collet
                      and
                      > the tool all were perfect the resulting axis of rotation at the
                      > cutter would have zero run out. But those parts are never perfect.
                      > Each will add more error, the final total run out at the cutting
                      > point can be much more than we realize. Buy the most expensive
                      > collets you can afford - because most of the error is usually in
                      that
                      > part. The spindle and the tool are usually pretty good.
                      >
                      > The circumferential run out of the inside my Homier spindle is
                      > about .00015"
                      >
                      > I purchased the most INexpensive collets money can buy and also a
                      8"
                      > length of precision ground .5000 diameter bar that is straight
                      > within .0001"
                      >
                      > When I measure the run out with that bar at 6" away from the
                      spindle
                      > seat it measures .004". Almost all of which is attributed to the
                      dam
                      > collet.
                      >
                      > When I put the drill chuck into the spindle and measure the run out
                      > at 6" away it measures a ridiculous .011" - You can see it wobble!
                      >
                      > And, these measurements are only averages. They change depending
                      how
                      > much I tighten the draw bar and how far I insert the .5000 dia bar
                      > into the collett. I was really surprised at the amounts of, and non-
                      > repeatability of, the runouts. Maybe that is why you gotta pay a
                      > small fortune for a really accurate machine. Ya think?
                      >
                      > And as far as Tramming the Mini Mill about the spindle axis? That
                      is
                      > for sure the single most important alignment to make, but there
                      are
                      > other factors to consider. The spindle axis not only needs to be
                      > square to the bed, it also needs to be parallel with the "Z" axis
                      > (the column) in two planes or the cutter will move along the "X"
                      > or "Y" axis as it is is raised and lowered. The problem is that the
                      > Mini Mill is notorious for being shipped with the spindle axis not
                      > being parallel to the "Z" axis and there is no quick way to correct
                      > for it. For that matter there is no easy way to measure that amount
                      > of the error. For most of us we are never aware of that type of
                      error
                      > because it only shows up when we make long cuts in the "Z"
                      direction,
                      > like drilling a deep hole or attempting to finish the sides of a
                      bar
                      > at 90 degrees to the "XY" surface. Usually the oversized diameter
                      at
                      > the top of that deep hole, or the out of squareness of the sides
                      are
                      > not noticable.



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                    • Armand
                      Don t get me wrong. (As the original poster) my question was reall more what was considered normal run out for a mini-mill? As a complete machine tool novice
                      Message 10 of 12 , Jan 26, 2004
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                        Don't get me wrong. (As the original poster) my question was reall
                        more "what was considered normal run out for a mini-mill?"

                        As a complete machine tool novice I have no pre-concived notions that
                        my $399 machine would be as accurate as a professional/industrial
                        quality unit!

                        For all I know, everyone could have said .009" is just fine I'd
                        wouldn't know any better. Thanks for all the help.


                        --- In GrizHFMinimill@yahoogroups.com, "jjfear" <jjfear@i...> wrote:
                        > I don't have a name so I can't thank you personally for this post,
                        but
                        > I really appreciated it. I always suspected tha there was some
                        reason
                        > why Hardinge and Monarch lathes and Bridgeport mills cost a
                        magnitude
                        > of a hundred or thousand to our $300. lathes and $400. mills. I
                        > figured there must be some reason. (sic)
                        >
                      • dudeair
                        At several points in this discussion, members have alluded to the role that the operator plays in the accuracay of machining operations. No doubt about this
                        Message 11 of 12 , Jan 26, 2004
                        • 0 Attachment
                          At several points in this discussion, members have alluded to the
                          role that the operator plays in the accuracay of machining
                          operations. No doubt about this point. What has not been addressed
                          directly is how to deal with some of the INaccuracies discussed in
                          this thread.

                          It seems to me that the most important thing is what the cutter is
                          actually doing, not what the apparatus above it is doing. So, to
                          that end, I am going to adopt the practice of measuring runout with a
                          dial test indicator as close to the cutter as possible EACH TIME IT
                          IS MOUNTED. If the measured runout is excessive, I will loosen the
                          drawbar, and try rotating the cutter in the collet, or the collet in
                          the spindle, until I find the combination that minimizes runout at
                          the cutter. In this way, I am hoping to offset (those errors that
                          can be offset) as much as possible. Sort of like centering a
                          workpiece in a 4-jaw chuck, only with more variables. The process
                          could be simplified somewhat by knowing how much runout and parallax
                          your spindle has.

                          I guess one of the things we have to deal with as a consequence of
                          using sub-$500 machines, is working around the minor defects they
                          posses. So keep those dial indicators handy.

                          David
                        • Jerry S.
                          David, You will no doubt notice, when you try, that the R-8 collets have a longitudial keyway in them allowing them to only be inserted the same (one) way each
                          Message 12 of 12 , Jan 27, 2004
                          • 0 Attachment
                            David,
                                You will no doubt notice, when you try, that the R-8 collets have a longitudial keyway in them allowing them to only be inserted the same (one) way each and every time. I would suggest that you examine said keyway & spindle for burrs and espescially dirt or particles that can easily interfere with collet hence drill chuck, end mill or whatever, running concentrically. The spindle must be running true, the collet must be running true, and so on, as "stack-up" (accumilation of error) will occur. End-mill shanks will run concentric with the cutting edge of same.
                                While these are what I would call a "Hobby Machine" they are as capable of doing accurate work. But is limited by the skill and ability of the operator. Practice, practice, and practice some more.
                            Jerry S.
                            Hell, MI
                            ----- Original Message -----
                            From: dudeair
                            Sent: Monday, January 26, 2004 4:32 PM
                            Subject: [GrizHFMinimill] Re: Testing for accuracy?

                            At several points in this discussion, members have alluded to the
                            role that the operator plays in the accuracay of machining
                            operations.  No doubt about this point.  What has not been addressed
                            directly is how to deal with some of the INaccuracies discussed in
                            this thread.

                            It seems to me that the most important thing is what the cutter is
                            actually doing, not what the apparatus above it is doing.  So, to
                            that end, I am going to adopt the practice of measuring runout with a
                            dial test indicator as close to the cutter as possible EACH TIME IT
                            IS MOUNTED.  If the measured runout is excessive, I will loosen the
                            drawbar, and try rotating the cutter in the collet, or the collet in
                            the spindle, until I find the combination that minimizes runout at
                            the cutter.  In this way, I am hoping to offset (those errors that
                            can be offset) as much as possible.  Sort of like centering a
                            workpiece in a 4-jaw chuck, only with more variables.  The process
                            could be simplified somewhat by knowing how much runout and parallax
                            your spindle has.

                            I guess one of the things we have to deal with as a consequence of
                            using sub-$500 machines, is working around the minor defects they
                            posses.  So keep those dial indicators handy.

                            David




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