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Pinned Table for Fixture (started in DM45table has 3 T slots)

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  • clumsysoftballerz
    I finished pinning my small X3 table last night and have some findings others may find useful. I followed the example found on ihcnc.com under tips. I found
    Message 1 of 11 , Sep 20, 2011
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      I finished pinning my small X3 table last night and have some findings others may find useful.

      I followed the example found on ihcnc.com under tips. I found the actual center of my extended travels and mapped out the center of the first flat in the Y+. I spaced the two holes 8" apart and (perhaps regrettably) I decided to use 3/16" pins and drill bushings because the 3/8+" hole for a 1/4" bushing seemed a little big for my little table.

      The process was strait forward. locate first hole with the last move being X+, spot drill, drill, ream, clean, move 8" X+, repeat. Inset bushings just below surface with loctite, let stand 24 hours. now came the issue- lap the bushings so a dowel pin to a slip fit on the dowel (i now recommend against this).


      Still following IH example I chucked a 3/16 dowel in a collet, smeared clover fine lapping paste, 400 rpm, SLOW hand feed for several minutes until it will slide all the way in. they said about 3 minutes which I found pretty accurate.

      PROBLEM- this process created a trapered bushing since the top ends up with double our more time being lapped then the bottom. the pin also reduces in diameter. when I insert a pin its a near perfect fit but there is a TINY but of runout allowed by the top being larger then the bottom.

      this is almost spitting hairs and if I was using 1/4 pins and perhaps 1/2" deep bushings it would likely be nil.

      RESULTS- honestly impressed me quite a bit. since the pins are fixed in the fixture the slight taper is pretty much mute. according to my DTI ($15 cheap chinese import) and my $400 Haimer 3D Taster (which trend to give near identical results on this type of stuff LOL) the fixture repeated its position (measured .1" from end of the 14.3125 plate) less than .0005" 6 out of 6 times. the only way I could think of to measure this was with an indicol type holder with DTI. I checked my backlash at (unreadable) 5 times doing a 50ipm X+1, remove fixture, replace, X-1.

      I plan on using DTI in same location when tightening mounting bolts and will give results.

      Then I checked for flex by using magnetic base and DTI mounted to the table in approximately the same location and wasn't very surprised that pushing on the front our pulling from the back only had perhaps .0001ish deflection. However when I twisted from the ends I was able to read up to .0025" deflection. each tome (perhaps 30 or more between the two ends it sprang back to within a tenth of 0. I'm guessing the flex is in the pins themselves and is likely only allowed BECAUSE of the slight taper in the bushings. I think .250 pins would lessen this, and having lapped the pins to fit the stock bushings would further decrease it.

      Overall I'm very happy with the results and it falls far within my required accuracy requirements

      I still need to create countersunk holes for 3/8-16 SHCS with washer, then I will resurface and start making the actual fixture
    • clumsysoftballerz
      I finished pinning my small X3 table last night and have some findings others may find useful. I followed the example found on ihcnc.com under tips. I found
      Message 2 of 11 , Sep 20, 2011
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        I finished pinning my small X3 table last night and have some findings others may find useful.

        I followed the example found on ihcnc.com under tips. I found the actual center of my extended travels and mapped out the center of the first flat in the Y+. I spaced the two holes 8" apart and (perhaps regrettably) I decided to use 3/16" pins and drill bushings because the 3/8+" hole for a 1/4" bushing seemed a little big for my little table.

        The process was strait forward. locate first hole with the last move being X+, spot drill, drill, ream, clean, move 8" X+, repeat. Inset bushings just below surface with loctite, let stand 24 hours. now came the issue- lap the bushings so a dowel pin to a slip fit on the dowel (i now recommend against this).


        Still following IH example I chucked a 3/16 dowel in a collet, smeared clover fine lapping paste, 400 rpm, SLOW hand feed for several minutes until it will slide all the way in. they said about 3 minutes which I found pretty accurate.

        PROBLEM- this process created a trapered bushing since the top ends up with double our more time being lapped then the bottom. the pin also reduces in diameter. when I insert a pin its a near perfect fit but there is a TINY but of runout allowed by the top being larger then the bottom.

        this is almost spitting hairs and if I was using 1/4 pins and perhaps 1/2" deep bushings it would likely be nil.

        RESULTS- honestly impressed me quite a bit. since the pins are fixed in the fixture the slight taper is pretty much mute. according to my DTI ($15 cheap chinese import) and my $400 Haimer 3D Taster (which trend to give near identical results on this type of stuff LOL) the fixture repeated its position (measured .1" from end of the 14.3125 plate) less than .0005" 6 out of 6 times. the only way I could think of to measure this was with an indicol type holder with DTI. I checked my backlash at (unreadable) 5 times doing a 50ipm X+1, remove fixture, replace, X-1.

        I plan on using DTI in same location when tightening mounting bolts and will give results.

        Then I checked for flex by using magnetic base and DTI mounted to the table in approximately the same location and wasn't very surprised that pushing on the front our pulling from the back only had perhaps .0001ish deflection. However when I twisted from the ends I was able to read up to .0025" deflection. each tome (perhaps 30 or more between the two ends it sprang back to within a tenth of 0. I'm guessing the flex is in the pins themselves and is likely only allowed BECAUSE of the slight taper in the bushings. I think .250 pins would lessen this, and having lapped the pins to fit the stock bushings would further decrease it.

        Overall I'm very happy with the results and it falls far within my required accuracy requirements

        I still need to create countersunk holes for 3/8-16 SHCS with washer, then I will resurface and start making the actual fixture
      • clumsysoftballerz
        forgot to mention (since rick asked yesterday) that removing the fixture was difficult at first since its impossible to grasp in a way that will allow you to
        Message 3 of 11 , Sep 20, 2011
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          forgot to mention (since rick asked yesterday) that removing the fixture was difficult at first since its impossible to grasp in a way that will allow you to pull perfectly strait up... a small screw driver in each hand into a t slot and it came strait up. I didn't have to pry, it just allowed even pull on both ends at the same time and it was very easy.



          --- In mill_drill@yahoogroups.com, "clumsysoftballerz" <mypersonalemailaccount@...> wrote:
          >
          > I finished pinning my small X3 table last night and have some findings others may find useful.
          >
          > I followed the example found on ihcnc.com under tips. I found the actual center of my extended travels and mapped out the center of the first flat in the Y+. I spaced the two holes 8" apart and (perhaps regrettably) I decided to use 3/16" pins and drill bushings because the 3/8+" hole for a 1/4" bushing seemed a little big for my little table.
          >
          > The process was strait forward. locate first hole with the last move being X+, spot drill, drill, ream, clean, move 8" X+, repeat. Inset bushings just below surface with loctite, let stand 24 hours. now came the issue- lap the bushings so a dowel pin to a slip fit on the dowel (i now recommend against this).
          >
          >
          > Still following IH example I chucked a 3/16 dowel in a collet, smeared clover fine lapping paste, 400 rpm, SLOW hand feed for several minutes until it will slide all the way in. they said about 3 minutes which I found pretty accurate.
          >
          > PROBLEM- this process created a trapered bushing since the top ends up with double our more time being lapped then the bottom. the pin also reduces in diameter. when I insert a pin its a near perfect fit but there is a TINY but of runout allowed by the top being larger then the bottom.
          >
          > this is almost spitting hairs and if I was using 1/4 pins and perhaps 1/2" deep bushings it would likely be nil.
          >
          > RESULTS- honestly impressed me quite a bit. since the pins are fixed in the fixture the slight taper is pretty much mute. according to my DTI ($15 cheap chinese import) and my $400 Haimer 3D Taster (which trend to give near identical results on this type of stuff LOL) the fixture repeated its position (measured .1" from end of the 14.3125 plate) less than .0005" 6 out of 6 times. the only way I could think of to measure this was with an indicol type holder with DTI. I checked my backlash at (unreadable) 5 times doing a 50ipm X+1, remove fixture, replace, X-1.
          >
          > I plan on using DTI in same location when tightening mounting bolts and will give results.
          >
          > Then I checked for flex by using magnetic base and DTI mounted to the table in approximately the same location and wasn't very surprised that pushing on the front our pulling from the back only had perhaps .0001ish deflection. However when I twisted from the ends I was able to read up to .0025" deflection. each tome (perhaps 30 or more between the two ends it sprang back to within a tenth of 0. I'm guessing the flex is in the pins themselves and is likely only allowed BECAUSE of the slight taper in the bushings. I think .250 pins would lessen this, and having lapped the pins to fit the stock bushings would further decrease it.
          >
          > Overall I'm very happy with the results and it falls far within my required accuracy requirements
          >
          > I still need to create countersunk holes for 3/8-16 SHCS with washer, then I will resurface and start making the actual fixture
          >
        • Rick Sparber
          I m not positive I followed exactly what you are doing here but I think the challenge would be in making a second plate that matches the existing holes in the
          Message 4 of 11 , Sep 20, 2011
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            I'm not positive I followed exactly what you are doing here but I think the challenge would be in making a second plate that matches the existing holes in the table. Did you match drill the first holes?

            Rick
            Rick.Sparber.org

            On Sep 20, 2011, at 12:24 PM, "clumsysoftballerz" <mypersonalemailaccount@...> wrote:

            > forgot to mention (since rick asked yesterday) that removing the fixture was difficult at first since its impossible to grasp in a way that will allow you to pull perfectly strait up... a small screw driver in each hand into a t slot and it came strait up. I didn't have to pry, it just allowed even pull on both ends at the same time and it was very easy.
          • clumsysoftballerz
            no need to match drill. all that needs to be done is two holes need to be drilled into any plate 8 apart and dowel pins inserted into the holes. even if the
            Message 5 of 11 , Sep 21, 2011
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              no need to match drill. all that needs to be done is two holes need to be drilled into any plate 8" apart and dowel pins inserted into the holes. even if the holes were drilled (for sake of example) 45 degrees off of the correct alignment, or 1" off center out it wouldn't matter. as long as they are 8" artist they will fit into the bushings in the table.

              this is just a blank fixture plate. nothing on it. now that its located to the table I can machine it as you would a "soft pad". the only difference is I can take it off, put it back on 2 months from now and it will still be aligned in X &Y. all I need to do is indicate Z, and my origin point.

              --- In mill_drill@yahoogroups.com, Rick Sparber <rgsparber@...> wrote:
              >
              > I'm not positive I followed exactly what you are doing here but I think the challenge would be in making a second plate that matches the existing holes in the table. Did you match drill the first holes?
              >
              > Rick
              > Rick.Sparber.org
              >
              > On Sep 20, 2011, at 12:24 PM, "clumsysoftballerz" <mypersonalemailaccount@...> wrote:
              >
              > > forgot to mention (since rick asked yesterday) that removing the fixture was difficult at first since its impossible to grasp in a way that will allow you to pull perfectly strait up... a small screw driver in each hand into a t slot and it came strait up. I didn't have to pry, it just allowed even pull on both ends at the same time and it was very easy.
              >
            • RG Sparber
              My concern is not in the alignment of the plate on the table but rather the distance between pins. Given the sliding fit you have for each pin, if the center
              Message 6 of 11 , Sep 21, 2011
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                My concern is not in the alignment of the plate on the table but rather the
                distance between pins. Given the sliding fit you have for each pin, if the
                center were 8.002" apart, they might bind up.

                Rick

                -----Original Message-----
                From: mill_drill@yahoogroups.com [mailto:mill_drill@yahoogroups.com] On
                Behalf Of clumsysoftballerz
                Sent: Wednesday, September 21, 2011 8:41 AM
                To: mill_drill@yahoogroups.com
                Subject: [mill_drill] Re: Pinned Table for Fixture (started in DM45table has
                3 T slots)

                no need to match drill. all that needs to be done is two holes need to be
                drilled into any plate 8" apart and dowel pins inserted into the holes. even
                if the holes were drilled (for sake of example) 45 degrees off of the
                correct alignment, or 1" off center out it wouldn't matter. as long as they
                are 8" apart they will fit into the bushings in the table.

                this is just a blank fixture plate. nothing on it. now that its located to
                the table I can machine it as you would a "soft pad". the only difference is
                I can take it off, put it back on 2 months from now and it will still be
                aligned in X &Y. all I need to do is indicate Z, and my origin point.
              • clumsysoftballerz
                I imagine they would, but thats pretty sloppy. even my cheap little mill could repeat the same single axis single direction movement within immeasurable (with
                Message 7 of 11 , Sep 21, 2011
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                  I imagine they would, but thats pretty sloppy. even my cheap little mill could repeat the same single axis single direction movement within immeasurable (with my means) distance. if you turn your hand wheel 8" worth to drill the table and its actually 8.002" then when you turn it 8" for the pins it should also be 8.002" and would for perfectly. if not the fixture is a mute point since the mill is so badly adjusted/worn that it won't benefit from the fixture plate in the first place.


                  I can repeat within a few tenths on a straight line with no backlash compensation complicating things. if I had run this program going back and fourth doing both holes at the same time I would likely have enough error that they wouldn't fit. as it is I wonder if I expected less accuracy than what I got because they just "fall" right in.


                  I guess the fixture plates are more useful for cnc, but I'm planning on pinning a plate with each of my vices etc too so alignment should take maybe one tap our just applying pressure in one direction while tightening the second bolt to keep the indicator back on zero.

                  might make a good article showing how to do it manually though.

                  --- In mill_drill@yahoogroups.com, "RG Sparber" <rgsparber@...> wrote:
                  >
                  > My concern is not in the alignment of the plate on the table but rather the
                  > distance between pins. Given the sliding fit you have for each pin, if the
                  > center were 8.002" apart, they might bind up.
                  >
                  > Rick
                  >
                  > -----Original Message-----
                  > From: mill_drill@yahoogroups.com [mailto:mill_drill@yahoogroups.com] On
                  > Behalf Of clumsysoftballerz
                  > Sent: Wednesday, September 21, 2011 8:41 AM
                  > To: mill_drill@yahoogroups.com
                  > Subject: [mill_drill] Re: Pinned Table for Fixture (started in DM45table has
                  > 3 T slots)
                  >
                  > no need to match drill. all that needs to be done is two holes need to be
                  > drilled into any plate 8" apart and dowel pins inserted into the holes. even
                  > if the holes were drilled (for sake of example) 45 degrees off of the
                  > correct alignment, or 1" off center out it wouldn't matter. as long as they
                  > are 8" apart they will fit into the bushings in the table.
                  >
                  > this is just a blank fixture plate. nothing on it. now that its located to
                  > the table I can machine it as you would a "soft pad". the only difference is
                  > I can take it off, put it back on 2 months from now and it will still be
                  > aligned in X &Y. all I need to do is indicate Z, and my origin point.
                  >
                • Druid Noibn
                  Hi,   Just curipous about the lead accuracy of the lead screw in these system - it is not too likely that this is common data, but I may be in error.   I do
                  Message 8 of 11 , Sep 21, 2011
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                    Hi,
                     
                    Just curipous about the lead accuracy of the lead screw in these system - it is not too likely that this is common data, but I may be in error.
                     
                    I do recall that numbers like 0.006"/foot are not unusual - and that is just for the leadscrew itself.
                     
                    Of course accuracy and repeatability are not the same and one can have unmeasureable (with our typical instruments) repeatability and be signficantly wrong in absolute measurement.
                     
                    Kind regards,
                    DBN

                    --- On Wed, 9/21/11, clumsysoftballerz <mypersonalemailaccount@...> wrote:

                    From: clumsysoftballerz <mypersonalemailaccount@...>
                    Subject: [mill_drill] Re: Pinned Table for Fixture (started in DM45table has 3 T slots)
                    To: mill_drill@yahoogroups.com
                    Date: Wednesday, September 21, 2011, 4:27 PM

                     
                    I imagine they would, but thats pretty sloppy. even my cheap little mill could repeat the same single axis single direction movement within immeasurable (with my means) distance. if you turn your hand wheel 8" worth to drill the table and its actually 8.002" then when you turn it 8" for the pins it should also be 8.002" and would for perfectly. if not the fixture is a mute point since the mill is so badly adjusted/worn that it won't benefit from the fixture plate in the first place.

                    I can repeat within a few tenths on a straight line with no backlash compensation complicating things. if I had run this program going back and fourth doing both holes at the same time I would likely have enough error that they wouldn't fit. as it is I wonder if I expected less accuracy than what I got because they just "fall" right in.

                    I guess the fixture plates are more useful for cnc, but I'm planning on pinning a plate with each of my vices etc too so alignment should take maybe one tap our just applying pressure in one direction while tightening the second bolt to keep the indicator back on zero.

                    might make a good article showing how to do it manually though.

                    --- In mill_drill@yahoogroups.com, "RG Sparber" <rgsparber@...> wrote:
                    >
                    > My concern is not in the alignment of the plate on the table but rather the
                    > distance between pins. Given the sliding fit you have for each pin, if the
                    > center were 8.002" apart, they might bind up.
                    >
                    > Rick
                    >
                    > -----Original Message-----
                    > From: mill_drill@yahoogroups.com [mailto:mill_drill@yahoogroups.com] On
                    > Behalf Of clumsysoftballerz
                    > Sent: Wednesday, September 21, 2011 8:41 AM
                    > To: mill_drill@yahoogroups.com
                    > Subject: [mill_drill] Re: Pinned Table for Fixture (started in DM45table has
                    > 3 T slots)
                    >
                    > no need to match drill. all that needs to be done is two holes need to be
                    > drilled into any plate 8" apart and dowel pins inserted into the holes. even
                    > if the holes were drilled (for sake of example) 45 degrees off of the
                    > correct alignment, or 1" off center out it wouldn't matter. as long as they
                    > are 8" apart they will fit into the bushings in the table.
                    >
                    > this is just a blank fixture plate. nothing on it. now that its located to
                    > the table I can machine it as you would a "soft pad". the only difference is
                    > I can take it off, put it back on 2 months from now and it will still be
                    > aligned in X &Y. all I need to do is indicate Z, and my origin point.
                    >

                  • clumsysoftballerz
                    pretty much nailed it. my ball screws are, precision , not ground so there is definitely some error however it is accounted for in the fact that my steps per
                    Message 9 of 11 , Sep 21, 2011
                    • 0 Attachment
                      pretty much nailed it. my ball screws are,"precision", not ground so there is definitely some error however it is accounted for in the fact that my steps per inch were set using 2x 123 blocks to create moves of 6" that register no visual error on a .0005 dti. the only error would be from the 123 blocks which is far less than I'm concerned with.

                      I do however have a few thou backlash and the backlash comp is good but not perfect. if I run an hour program I check the origin again and its usually a thou or so off in X and a little less in Y.

                      but none of that really applies to the fixture plate since its a single move done twice on the same mill. it should be repeatable within the requirements of this purpose. mine obviously was because it was a perfect fit. but if I had the ability to measure the pins with a higher level of accuracy I wouldn't be surprised if they were .0005 off from true 8".

                      --- In mill_drill@yahoogroups.com, Druid Noibn <druid_noibn@...> wrote:
                      >
                      > Hi,
                      >  
                      > Just curipous about the lead accuracy of the lead screw in these system - it is not too likely that this is common data, but I may be in error.
                      >  
                      > I do recall that numbers like 0.006"/foot are not unusual - and that is just for the leadscrew itself.
                      >  
                      > Of course accuracy and repeatability are not the same and one can have unmeasureable (with our typical instruments) repeatability and be signficantly wrong in absolute measurement.
                      >  
                      > Kind regards,
                      > DBN
                      >
                      > --- On Wed, 9/21/11, clumsysoftballerz <mypersonalemailaccount@...> wrote:
                      >
                      >
                      > From: clumsysoftballerz <mypersonalemailaccount@...>
                      > Subject: [mill_drill] Re: Pinned Table for Fixture (started in DM45table has 3 T slots)
                      > To: mill_drill@yahoogroups.com
                      > Date: Wednesday, September 21, 2011, 4:27 PM
                      >
                      >
                      >  
                      >
                      >
                      >
                      > I imagine they would, but thats pretty sloppy. even my cheap little mill could repeat the same single axis single direction movement within immeasurable (with my means) distance. if you turn your hand wheel 8" worth to drill the table and its actually 8.002" then when you turn it 8" for the pins it should also be 8.002" and would for perfectly. if not the fixture is a mute point since the mill is so badly adjusted/worn that it won't benefit from the fixture plate in the first place.
                      >
                      > I can repeat within a few tenths on a straight line with no backlash compensation complicating things. if I had run this program going back and fourth doing both holes at the same time I would likely have enough error that they wouldn't fit. as it is I wonder if I expected less accuracy than what I got because they just "fall" right in.
                      >
                      > I guess the fixture plates are more useful for cnc, but I'm planning on pinning a plate with each of my vices etc too so alignment should take maybe one tap our just applying pressure in one direction while tightening the second bolt to keep the indicator back on zero.
                      >
                      > might make a good article showing how to do it manually though.
                      >
                      > --- In mill_drill@yahoogroups.com, "RG Sparber" <rgsparber@> wrote:
                      > >
                      > > My concern is not in the alignment of the plate on the table but rather the
                      > > distance between pins. Given the sliding fit you have for each pin, if the
                      > > center were 8.002" apart, they might bind up.
                      > >
                      > > Rick
                      > >
                      > > -----Original Message-----
                      > > From: mill_drill@yahoogroups.com [mailto:mill_drill@yahoogroups.com] On
                      > > Behalf Of clumsysoftballerz
                      > > Sent: Wednesday, September 21, 2011 8:41 AM
                      > > To: mill_drill@yahoogroups.com
                      > > Subject: [mill_drill] Re: Pinned Table for Fixture (started in DM45table has
                      > > 3 T slots)
                      > >
                      > > no need to match drill. all that needs to be done is two holes need to be
                      > > drilled into any plate 8" apart and dowel pins inserted into the holes. even
                      > > if the holes were drilled (for sake of example) 45 degrees off of the
                      > > correct alignment, or 1" off center out it wouldn't matter. as long as they
                      > > are 8" apart they will fit into the bushings in the table.
                      > >
                      > > this is just a blank fixture plate. nothing on it. now that its located to
                      > > the table I can machine it as you would a "soft pad". the only difference is
                      > > I can take it off, put it back on 2 months from now and it will still be
                      > > aligned in X &Y. all I need to do is indicate Z, and my origin point.
                      > >
                      >
                    • RG Sparber
                      DBN, For those that don t have your precision, it might be useful to make up a drilling plate with the two holes in it. I would then use the plate to drill my
                      Message 10 of 11 , Sep 21, 2011
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                        DBN,

                        For those that don't have your precision, it might be useful to make up a
                        drilling plate with the two holes in it. I would then use the plate to drill
                        my first hole in the mill table. Then pin it. Drill the second hole through
                        the plate and into the table. Then use this drilling plate to make all of my
                        fixture plates. Even better, put hardened drill guides in the plate.

                        Rick

                        -----Original Message-----
                        From: mill_drill@yahoogroups.com [mailto:mill_drill@yahoogroups.com] On
                        Behalf Of clumsysoftballerz
                        Sent: Wednesday, September 21, 2011 2:54 PM
                        To: mill_drill@yahoogroups.com
                        Subject: [mill_drill] Re: Pinned Table for Fixture (started in DM45table has
                        3 T slots)

                        pretty much nailed it. my ball screws are,"precision", not ground so there
                        is definitely some error however it is accounted for in the fact that my
                        steps per inch were set using 2x 123 blocks to create moves of 6" that
                        register no visual error on a .0005 dti. the only error would be from the
                        123 blocks which is far less than I'm concerned with.

                        I do however have a few thou backlash and the backlash comp is good but not
                        perfect. if I run an hour program I check the origin again and its usually a
                        thou or so off in X and a little less in Y.

                        but none of that really applies to the fixture plate since its a single move
                        done twice on the same mill. it should be repeatable within the requirements
                        of this purpose. mine obviously was because it was a perfect fit. but if I
                        had the ability to measure the pins with a higher level of accuracy I
                        wouldn't be surprised if they were .0005 off from true 8".
                      • Druid Noibn
                        Hi Rick,   That wasn t me   I only asked a leading question.   Ta, DBN ... From: RG Sparber Subject: RE: [mill_drill] Re:
                        Message 11 of 11 , Sep 22, 2011
                        • 0 Attachment
                          Hi Rick,
                           
                          That wasn't me <smile>  I only asked a "leading question."
                           
                          Ta,
                          DBN

                          --- On Wed, 9/21/11, RG Sparber <rgsparber@...> wrote:

                          From: RG Sparber <rgsparber@...>
                          Subject: RE: [mill_drill] Re: Pinned Table for Fixture (started in DM45table has 3 T slots)
                          To: mill_drill@yahoogroups.com
                          Date: Wednesday, September 21, 2011, 9:59 PM

                           
                          DBN,

                          For those that don't have your precision, it might be useful to make up a
                          drilling plate with the two holes in it. I would then use the plate to drill
                          my first hole in the mill table. Then pin it. Drill the second hole through
                          the plate and into the table. Then use this drilling plate to make all of my
                          fixture plates. Even better, put hardened drill guides in the plate.

                          Rick

                          -----Original Message-----
                          From: mill_drill@yahoogroups.com [mailto:mill_drill@yahoogroups.com] On
                          Behalf Of clumsysoftballerz
                          Sent: Wednesday, September 21, 2011 2:54 PM
                          To: mill_drill@yahoogroups.com
                          Subject: [mill_drill] Re: Pinned Table for Fixture (started in DM45table has
                          3 T slots)

                          pretty much nailed it. my ball screws are,"precision", not ground so there
                          is definitely some error however it is accounted for in the fact that my
                          steps per inch were set using 2x 123 blocks to create moves of 6" that
                          register no visual error on a .0005 dti. the only error would be from the
                          123 blocks which is far less than I'm concerned with.

                          I do however have a few thou backlash and the backlash comp is good but not
                          perfect. if I run an hour program I check the origin again and its usually a
                          thou or so off in X and a little less in Y.

                          but none of that really applies to the fixture plate since its a single move
                          done twice on the same mill. it should be repeatable within the requirements
                          of this purpose. mine obviously was because it was a perfect fit. but if I
                          had the ability to measure the pins with a higher level of accuracy I
                          wouldn't be surprised if they were .0005 off from true 8".

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