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Re: hole drilling question

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  • randympowell
    Jerry, Well, I was drilling the hole down the center of the piece, not on the curved edge. I m afraid I cheated on the centering problem. I used a piece of
    Message 1 of 13 , Apr 30, 2003
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      Jerry,

      Well, I was drilling the hole down the center of the piece, not on
      the curved edge. I'm afraid I cheated on the centering problem. I
      used a piece of dowel stock in the collet and slid the other end into
      the rotary table. Tightened everything down and then clamped the
      rotary table to the bead. Instant centering. <blush>

      Hey, it works.

      Randy

      --- In GrizHFMinimill@yahoogroups.com, "jjfear" <jjfear@i...> wrote:
      >
      > Daves suggestion is most importsnt, all drill bits will wander,
      even
      > more so on a round surface. No matter how perfectly you have the
      > piece centered, you will not drill a centered hole with out a
      > center-drilled starting point.
      >
      > As to the centering problem, there are several ways to do it,
      > depending on the equipment you have.
      >
      > The most common technically correct method, is to use an edge finder
      > in your chuck. Yhey have an end that is spring loaded and will
      > deflect at the moment of contact with the edge of the work. Then
      you
      > subtract 1/2 the diameter of the edge finder probe and half the
      > diameter of the work piece. Ad these figures, then set up a Dial
      > indicator and movr the table exactly that amount. (Just a reminder
      > about backlash, you always do all your movements in one
      > direction--never back up--this will throw off all your
      measurements.)
      >
      > The problem with this method is with round stock, their two centers
      > you have to find, because the edge finder must contact the exact
      > center of the side of the workpiece or the measurements.
      >
      > This can be calculated, similar as before, as distance from the
      table
      > to the top of the work piece divided by two.
      >
      > There is an easy way to accomplish this task. Take a double edged
      > razor blade, one of the leaves of a feeler guage, or ecen a six inch
      > shop rule. Put a center drill in the chuck, and place the piece
      > between the drill and work. Lower the dril to hold this piece.
      >
      > The only way the the shim's ends will be an equal distance from the
      > table is if the drill is at the exact center of the work. There are
      > several easy ways to measues that distance.
      >
      > It took me longer to explain than for you to do. Eyeballing will
      get
      > you within a few 100 thousand, careful measurement, will get you
      dead on.
      >
      > HTH
      > Jerry Fear
      >
      >
      > --- In GrizHFMinimill@yahoogroups.com, "randympowell"
      > <stunter2001@c...> wrote:
      > > Hi folks,
      > >
      > > I'm making a sort of weird nut. I need to drill a #6 sized hole
      > > exactly down the center of a piece of 5/8" diameter by 2" long
      steel
      > > dowel (lengthwise). I tried centering it up using a rotary table
      and
      > > chuck and just drilling the hole down the middle with a drill
      bit,
      > > but I haven't been able to get it exactly in the center. The
      piece is
      > > centered on the chuck and z-axis, but the drill bit walks around
      a
      > > bit and no matter how careful I am, I haven't been able to get it
      > > exactly in the center. This thing is going to have to spin at
      about
      > > 11,000 rpm, so it needs to be as exactly in the center as I can
      make
      > > it.
      > >
      > > The nut itself is, as noted, will be about 2" long. It will have
      an
      > > 11mm hex on one end (about 1/2" of the length) and the rest of
      the
      > > dowel will
      > > be turned down to 11/32" with a threaded 7mm hole down the center.
      > >
      > > Hope that's clear. I'm pretty new to machining and haven't worked
      > > with steel before. Just aluminum.
      > >
      > > Thanks for any help. I've made 3 tries. One pretty close, but no
      > > cigar. I have a couple of other idea on how to get it done, but
      > > thought I'd ask the people that actually know what they're doing.
      > >
      > > Randy
    • jjfear
      Randy, I m sorry I misread your question. I didn t even think about centering a piece the long way, thiugh you clearly state thst. As Brian said, most of us
      Message 2 of 13 , May 1, 2003
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        Randy,
        I'm sorry I misread your question. I didn't even think about
        centering a piece the long way, thiugh you clearly state thst. As
        Brian said, most of us do this task on a lathe, and unless the
        headstock and tailstock are not alligned, it's actually hard to drill
        an off center hole.

        Hopefully the info will help someone else at some point

        Jerry Fear




        --- In GrizHFMinimill@yahoogroups.com, "randympowell"
        <stunter2001@c...> wrote:
        > Jerry,
        >
        > Well, I was drilling the hole down the center of the piece, not on
        > the curved edge. I'm afraid I cheated on the centering problem. I
        > used a piece of dowel stock in the collet and slid the other end into
        > the rotary table. Tightened everything down and then clamped the
        > rotary table to the bead. Instant centering. <blush>
        >
        > Hey, it works.
        >
        > Randy
        >
        > --- In GrizHFMinimill@yahoogroups.com, "jjfear" <jjfear@i...> wrote:
        > >
        > > Daves suggestion is most importsnt, all drill bits will wander,
        > even
        > > more so on a round surface. No matter how perfectly you have the
        > > piece centered, you will not drill a centered hole with out a
        > > center-drilled starting point.
        > >
        > > As to the centering problem, there are several ways to do it,
        > > depending on the equipment you have.
        > >
        > > The most common technically correct method, is to use an edge finder
        > > in your chuck. Yhey have an end that is spring loaded and will
        > > deflect at the moment of contact with the edge of the work. Then
        > you
        > > subtract 1/2 the diameter of the edge finder probe and half the
        > > diameter of the work piece. Ad these figures, then set up a Dial
        > > indicator and movr the table exactly that amount. (Just a reminder
        > > about backlash, you always do all your movements in one
        > > direction--never back up--this will throw off all your
        > measurements.)
        > >
        > > The problem with this method is with round stock, their two centers
        > > you have to find, because the edge finder must contact the exact
        > > center of the side of the workpiece or the measurements.
        > >
        > > This can be calculated, similar as before, as distance from the
        > table
        > > to the top of the work piece divided by two.
        > >
        > > There is an easy way to accomplish this task. Take a double edged
        > > razor blade, one of the leaves of a feeler guage, or ecen a six inch
        > > shop rule. Put a center drill in the chuck, and place the piece
        > > between the drill and work. Lower the dril to hold this piece.
        > >
        > > The only way the the shim's ends will be an equal distance from the
        > > table is if the drill is at the exact center of the work. There are
        > > several easy ways to measues that distance.
        > >
        > > It took me longer to explain than for you to do. Eyeballing will
        > get
        > > you within a few 100 thousand, careful measurement, will get you
        > dead on.
        > >
        > > HTH
        > > Jerry Fear
        > >
        > >
        > > --- In GrizHFMinimill@yahoogroups.com, "randympowell"
        > > <stunter2001@c...> wrote:
        > > > Hi folks,
        > > >
        > > > I'm making a sort of weird nut. I need to drill a #6 sized hole
        > > > exactly down the center of a piece of 5/8" diameter by 2" long
        > steel
        > > > dowel (lengthwise). I tried centering it up using a rotary table
        > and
        > > > chuck and just drilling the hole down the middle with a drill
        > bit,
        > > > but I haven't been able to get it exactly in the center. The
        > piece is
        > > > centered on the chuck and z-axis, but the drill bit walks around
        > a
        > > > bit and no matter how careful I am, I haven't been able to get it
        > > > exactly in the center. This thing is going to have to spin at
        > about
        > > > 11,000 rpm, so it needs to be as exactly in the center as I can
        > make
        > > > it.
        > > >
        > > > The nut itself is, as noted, will be about 2" long. It will have
        > an
        > > > 11mm hex on one end (about 1/2" of the length) and the rest of
        > the
        > > > dowel will
        > > > be turned down to 11/32" with a threaded 7mm hole down the center.
        > > >
        > > > Hope that's clear. I'm pretty new to machining and haven't worked
        > > > with steel before. Just aluminum.
        > > >
        > > > Thanks for any help. I've made 3 tries. One pretty close, but no
        > > > cigar. I have a couple of other idea on how to get it done, but
        > > > thought I'd ask the people that actually know what they're doing.
        > > >
        > > > Randy
      • Rick Kruger
        That s not cheating, that s using the noodle. I do that sort of centering all the time by using a MT3 dead center in the spindle, bring the head down to drive
        Message 3 of 13 , May 1, 2003
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          That's not cheating, that's using the noodle. I do that sort of centering
          all the time by using a MT3 dead center in the spindle, bring the head down
          to drive the center into the RT hole, clamp the head down tight and secure
          the RT.

          Rick

          At 05:28 AM 5/1/03 +0000, you wrote:
          >Jerry,
          >
          >Well, I was drilling the hole down the center of the piece, not on the
          >curved edge. I'm afraid I cheated on the centering problem. I used a piece
          >of dowel stock in the collet and slid the other end into the rotary table.
          >Tightened everything down and then clamped the rotary table to the bead.
          >Instant centering. <blush>
          >
          >Hey, it works.
          >
          >Randy
        • randympowell
          Jerry, Here what I posted in the home machinist group about how I managed to get this job done. Just a follow up. As I noted, I don t own a lathe, but am
          Message 4 of 13 , May 2, 2003
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            Jerry,

            Here what I posted in the home machinist group about how I managed to
            get this job done.

            Just a follow up. As I noted, I don't own a lathe, but am thinking
            about getting one. Here was my final solution using only my mill.

            I drilled the hole in the 5/8" round stock length-wise using the mill
            with the stock set vertically . I used a rotary table and chuck to
            mount it and just centered it and drilled the hole. It was pretty
            close, but not perfect. I tapped the hole (m7x1) and screwed in a
            stud about 3/4 the length of the hole. I used a thin nut to secure it
            against the end of the piece. I mounted the rotary table at 90
            degrees and mounted the piece with the stud end in the rotary table
            chuck and the other end was supported using a tailstock and live
            center. I'd have preferred to run the stud all the way through and
            use a small chuck in the tailstock, but a live center is what i had.

            Then I just used the tapped hole as the center and turned the piece
            down. This is a real pain and took way longer than it would have on a
            lathe, but it worked pretty well and gave a decent surface. Moving
            the piece lengthwise about .010 at a time, rotate it 360 degrees and
            move it another .010. It just took forever. I made several passes
            taking off about .030 with each pass. I used a pretty big endmill
            initially, then a very small 4 flute job for the final pass. 3/4 of
            the length was machined down to the 11/32", I pulled the whole mess,
            remounted the rotary table vertically and put the end that I had just
            turned into the rotary table and squared up the other end to the just
            machined area. Re-setup the horizontal configuration and now I'm
            cutting the hex for the nut end.

            All and all, a real pain to do this way, but it worked fine and the
            the nut is certainly square. An operation that would probably have
            taken a 1/2 hour on a lathe was a several hour project on the mill,
            but hey, it can be done at need.

            Thanks for all the input.

            randy


            --- In GrizHFMinimill@yahoogroups.com, "jjfear" <jjfear@i...> wrote:
            > Randy,
            > I'm sorry I misread your question. I didn't even think about
            > centering a piece the long way, thiugh you clearly state thst. As
            > Brian said, most of us do this task on a lathe, and unless the
            > headstock and tailstock are not alligned, it's actually hard to
            drill
            > an off center hole.
            >
            > Hopefully the info will help someone else at some point
            >
            > Jerry Fear
          • dswr@webtv.net
            Randy, That s a ingenious use of the mini-mill and a rotary table! Thanks for the description of the process. Leo (pearland, tx)
            Message 5 of 13 , May 2, 2003
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              Randy,

              That's a ingenious use of the mini-mill and a rotary table!

              Thanks for the description of the process.

              Leo (pearland, tx)
            • Barry Young
              Hi Randy: Drill a pilot for your twist drill with a center drill. This is nice and rigid and will not wander. Barry Young ...
              Message 6 of 13 , May 10, 2003
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                Hi Randy:

                Drill a pilot for your twist drill with a center
                drill. This is nice and rigid and will not wander.

                Barry Young


                --- randympowell <stunter2001@...> wrote:
                > Hi folks,
                >
                > I'm making a sort of weird nut. I need to drill a #6
                > sized hole
                > exactly down the center of a piece of 5/8" diameter
                > by 2" long steel
                > dowel (lengthwise). I tried centering it up using a
                > rotary table and
                > chuck and just drilling the hole down the middle
                > with a drill bit,
                > but I haven't been able to get it exactly in the
                > center. The piece is
                > centered on the chuck and z-axis, but the drill bit
                > walks around a
                > bit and no matter how careful I am, I haven't been
                > able to get it
                > exactly in the center. This thing is going to have
                > to spin at about
                > 11,000 rpm, so it needs to be as exactly in the
                > center as I can make
                > it.
                >
                > The nut itself is, as noted, will be about 2" long.
                > It will have an
                > 11mm hex on one end (about 1/2" of the length) and
                > the rest of the
                > dowel will
                > be turned down to 11/32" with a threaded 7mm hole
                > down the center.
                >
                > Hope that's clear. I'm pretty new to machining and
                > haven't worked
                > with steel before. Just aluminum.
                >
                > Thanks for any help. I've made 3 tries. One pretty
                > close, but no
                > cigar. I have a couple of other idea on how to get
                > it done, but
                > thought I'd ask the people that actually know what
                > they're doing.
                >
                > Randy
                >
                >
                > ------------------------ Yahoo! Groups Sponsor
                >
                > To unsubscribe from this group, send an email to:
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                >
                >
                >
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                > http://docs.yahoo.com/info/terms/
                >
                >


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              • Barry Young
                It may be hard, but some of us manage to drill off center holes in the lathe now and then. Barry Young ... __________________________________ Do you Yahoo!?
                Message 7 of 13 , May 10, 2003
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                  It may be hard, but some of us manage to drill off
                  center holes in the lathe now and then.

                  Barry Young


                  --- jjfear <jjfear@...> wrote:
                  > Randy,
                  > I'm sorry I misread your question. I didn't even
                  > think about
                  > centering a piece the long way, thiugh you clearly
                  > state thst. As
                  > Brian said, most of us do this task on a lathe, and
                  > unless the
                  > headstock and tailstock are not alligned, it's
                  > actually hard to drill
                  > an off center hole.
                  >
                  > Hopefully the info will help someone else at some
                  > point
                  >
                  > Jerry Fear
                  >
                  >
                  >
                  >
                  > --- In GrizHFMinimill@yahoogroups.com,
                  > "randympowell"
                  > <stunter2001@c...> wrote:
                  > > Jerry,
                  > >
                  > > Well, I was drilling the hole down the center of
                  > the piece, not on
                  > > the curved edge. I'm afraid I cheated on the
                  > centering problem. I
                  > > used a piece of dowel stock in the collet and slid
                  > the other end into
                  > > the rotary table. Tightened everything down and
                  > then clamped the
                  > > rotary table to the bead. Instant centering.
                  > <blush>
                  > >
                  > > Hey, it works.
                  > >
                  > > Randy
                  > >
                  > > --- In GrizHFMinimill@yahoogroups.com, "jjfear"
                  > <jjfear@i...> wrote:
                  > > >
                  > > > Daves suggestion is most importsnt, all drill
                  > bits will wander,
                  > > even
                  > > > more so on a round surface. No matter how
                  > perfectly you have the
                  > > > piece centered, you will not drill a centered
                  > hole with out a
                  > > > center-drilled starting point.
                  > > >
                  > > > As to the centering problem, there are several
                  > ways to do it,
                  > > > depending on the equipment you have.
                  > > >
                  > > > The most common technically correct method, is
                  > to use an edge finder
                  > > > in your chuck. Yhey have an end that is spring
                  > loaded and will
                  > > > deflect at the moment of contact with the edge
                  > of the work. Then
                  > > you
                  > > > subtract 1/2 the diameter of the edge finder
                  > probe and half the
                  > > > diameter of the work piece. Ad these figures,
                  > then set up a Dial
                  > > > indicator and movr the table exactly that
                  > amount. (Just a reminder
                  > > > about backlash, you always do all your movements
                  > in one
                  > > > direction--never back up--this will throw off
                  > all your
                  > > measurements.)
                  > > >
                  > > > The problem with this method is with round
                  > stock, their two centers
                  > > > you have to find, because the edge finder must
                  > contact the exact
                  > > > center of the side of the workpiece or the
                  > measurements.
                  > > >
                  > > > This can be calculated, similar as before, as
                  > distance from the
                  > > table
                  > > > to the top of the work piece divided by two.
                  > > >
                  > > > There is an easy way to accomplish this task.
                  > Take a double edged
                  > > > razor blade, one of the leaves of a feeler
                  > guage, or ecen a six inch
                  > > > shop rule. Put a center drill in the chuck, and
                  > place the piece
                  > > > between the drill and work. Lower the dril to
                  > hold this piece.
                  > > >
                  > > > The only way the the shim's ends will be an
                  > equal distance from the
                  > > > table is if the drill is at the exact center of
                  > the work. There are
                  > > > several easy ways to measues that distance.
                  > > >
                  > > > It took me longer to explain than for you to do.
                  > Eyeballing will
                  > > get
                  > > > you within a few 100 thousand, careful
                  > measurement, will get you
                  > > dead on.
                  > > >
                  > > > HTH
                  > > > Jerry Fear
                  > > >
                  > > >
                  > > > --- In GrizHFMinimill@yahoogroups.com,
                  > "randympowell"
                  > > > <stunter2001@c...> wrote:
                  > > > > Hi folks,
                  > > > >
                  > > > > I'm making a sort of weird nut. I need to
                  > drill a #6 sized hole
                  > > > > exactly down the center of a piece of 5/8"
                  > diameter by 2" long
                  > > steel
                  > > > > dowel (lengthwise). I tried centering it up
                  > using a rotary table
                  > > and
                  > > > > chuck and just drilling the hole down the
                  > middle with a drill
                  > > bit,
                  > > > > but I haven't been able to get it exactly in
                  > the center. The
                  > > piece is
                  > > > > centered on the chuck and z-axis, but the
                  > drill bit walks around
                  > > a
                  > > > > bit and no matter how careful I am, I haven't
                  > been able to get it
                  > > > > exactly in the center. This thing is going to
                  > have to spin at
                  > > about
                  > > > > 11,000 rpm, so it needs to be as exactly in
                  > the center as I can
                  > > make
                  > > > > it.
                  > > > >
                  > > > > The nut itself is, as noted, will be about 2"
                  > long. It will have
                  > > an
                  > > > > 11mm hex on one end (about 1/2" of the length)
                  > and the rest of
                  > > the
                  > > > > dowel will
                  > > > > be turned down to 11/32" with a threaded 7mm
                  > hole down the center.
                  > > > >
                  > > > > Hope that's clear. I'm pretty new to machining
                  > and haven't worked
                  > > > > with steel before. Just aluminum.
                  > > > >
                  > > > > Thanks for any help. I've made 3 tries. One
                  > pretty close, but no
                  > > > > cigar. I have a couple of other idea on how to
                  > get it done, but
                  > > > > thought I'd ask the people that actually know
                  > what they're doing.
                  > > > >
                  > > > > Randy
                  >
                  >
                  > ------------------------ 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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