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Re: how true-up a disk cut from a bar?

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  • Kirk
    I run into the same problem since my portaband saw cuts about as straight as a drunk walking a line. I usually fix that problem by cutting a little extra and
    Message 1 of 13 , Mar 1, 2008
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      I run into the same problem since my portaband saw cuts about as
      straight as a drunk walking a line. I usually fix that problem by
      cutting a little extra and facing the piece in my lathe. If you don't
      have a lathe and only have a mill, then the only thing I can think of
      would be to get a set of V jaws for your vise, those should hold a
      piece of round stock vertically pretty good and square it up. Enco has
      a cheap magnetic set for $15, #891-5936. Or you could probably make a
      set if you milled a vertical slot in a pair of soft jaws on both sides.

      Kirk




      --- In mill_drill@yahoogroups.com, "John Dinan" <jdinan@...> wrote:
      >
      > I sliced a two cm thick slab from a round bar stock using a 4x6 band
      > saw that does not cut square to its table. So I have a disk whose ends
      > are not parallel to each other and are not at 90 degrees to the sides.
      > What steps do I take in a mill to true-up such a disk?
      >
    • Philip Burman
      What s your tolerance on parallel and 90 degrees ? What s the blank diameter? If you are not prepared to shell out for a lathe and want to do round things
      Message 2 of 13 , Mar 1, 2008
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        What's your tolerance on "parallel" and "90 degrees"? What's the blank
        diameter?

        If you are not prepared to shell out for a lathe and want to do "round
        things" on a mill then invest in a H/V rotary table and a chuck to
        mount on it.

        Phil

        --- In mill_drill@yahoogroups.com, "John Dinan" <jdinan@...> wrote:
        >
        > I sliced a two cm thick slab from a round bar stock using a 4x6 band
        > saw that does not cut square to its table. So I have a disk whose ends
        > are not parallel to each other and are not at 90 degrees to the sides.
        > What steps do I take in a mill to true-up such a disk?
        >
      • Philip Burman
        If you want a no cost alternative then: Cut 2 pieces of thick, flat bar say 1 longer than the blank diameter. Cut a 90 degree V in the middle of each such
        Message 3 of 13 , Mar 1, 2008
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          If you want a no cost alternative then:

          Cut 2 pieces of thick, flat bar say 1" longer than the blank
          diameter. Cut a 90 degree V in the middle of each such that the "Vee"
          width is at least equal to 50% of the blank diameter. Drill a through
          hole on both ends so you can clamp them to the blank. Using a square
          and shims under the blank square the blank to the table. Using 2
          lengths of threaded rod clamp the two pieces of flat "Vee" bar to the
          diameter of the blank so that the bars are approximately parallel to
          each other. Now clamp the parallel bars to the table. Machine the top
          face then repeat the whole procedure for the bottom face, you
          shouldn't need the shims for the second face.

          As you are starting to see, machining is not so much about running
          the cutter across the work it's actually more about how best to hold
          the work. This is going to come up time and time again. Personally at
          this point I would shell-out for a lathe.

          Phil

          --- In mill_drill@yahoogroups.com, "Philip Burman"
          <philip.burman@...> wrote:
          >
          > What's your tolerance on "parallel" and "90 degrees"? What's the
          blank
          > diameter?
          >
          > If you are not prepared to shell out for a lathe and want to
          do "round
          > things" on a mill then invest in a H/V rotary table and a chuck to
          > mount on it.
          >
          > Phil
          >
          > --- In mill_drill@yahoogroups.com, "John Dinan" <jdinan@> wrote:
          > >
          > > I sliced a two cm thick slab from a round bar stock using a 4x6
          band
          > > saw that does not cut square to its table. So I have a disk whose
          ends
          > > are not parallel to each other and are not at 90 degrees to the
          sides.
          > > What steps do I take in a mill to true-up such a disk?
          > >
          >
        • Norman Atkinson
          Phil, greetings from another part of the Lesser Lunacy! Of course, a mill is only a lathe tipped up at 90 degrees so he doesn t need to go out and buy a lathe
          Message 4 of 13 , Mar 1, 2008
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            Phil, greetings from another part of the Lesser Lunacy!

            Of course, a mill is only a lathe tipped up at 90 degrees so he
            doesn't need to go out and buy a lathe specially for such a simple
            task. He simply fixes the disc in the headstock chuck, clocks it and
            uses the mill table as the saddle and/ or the top slide as a lathe
            tool holder- and faces the disc. And that is that and as simple as
            having sex standing up in a hammock!

            Now the late George Thomas was parting off and not merely facing off
            discs parallel to 0.0002 inch and as he remarked 'You don't get much
            nearer than that'

            Ooops

            Norm
          • Philip Burman
            Hi Norman, Yes maybe. He calls it a a two cm thick slab which implies a diameter of maybe 3 or 4 . Not a good size for machining in the spindle of a
            Message 5 of 13 , Mar 1, 2008
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              Hi Norman,

              Yes maybe. He calls it a "a two cm thick slab " which implies a
              diameter of maybe 3 or 4". Not a good size for machining in the
              spindle of a mill/drill. To do it you need an arbor, maybe he doesn't
              want a hole through the middle of his work-piece. More imformation is
              needed.

              Phil

              PS: I'll bet even GT would have struggled parting off 4" discs in a
              Chinese 7x12.



              --- In mill_drill@yahoogroups.com, "Norman Atkinson" <norman@...>
              wrote:
              >
              >
              > Phil, greetings from another part of the Lesser Lunacy!
              >
              > Of course, a mill is only a lathe tipped up at 90 degrees so he
              > doesn't need to go out and buy a lathe specially for such a simple
              > task. He simply fixes the disc in the headstock chuck, clocks it
              and
              > uses the mill table as the saddle and/ or the top slide as a lathe
              > tool holder- and faces the disc. And that is that and as simple as
              > having sex standing up in a hammock!
              >
              > Now the late George Thomas was parting off and not merely facing
              off
              > discs parallel to 0.0002 inch and as he remarked 'You don't get
              much
              > nearer than that'
              >
              > Ooops
              >
              > Norm
              >
            • Jack Dinan
              Sorry everyone. The bar is 3 in diameter and its surface is as-received. I do have access to a 9 lathe and I m afraid that making the disk true by facing
              Message 6 of 13 , Mar 1, 2008
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                Sorry everyone. The bar is 3" in diameter and its surface is
                as-received. I do have access to a 9" lathe and I'm afraid that
                making the disk true by facing off in the lathe did not occur to me.
                I'll try both this and using the rotary table.
                Thanks much for all the ideas.
                Jack/John
              • Mike Klotz
                You didn t mention the diameter. Would it work to clamp it in the vise with a V block set vertical? The V block against one vice jaw, pressing the stock
                Message 7 of 13 , Mar 1, 2008
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                  You didn't mention the diameter.  Would it work to clamp it in the vise with a V block set vertical?  The V block against one vice jaw, pressing the stock against the other jaw.  Set the height of the slab with on parallel against the jaw that's not touching the V block.  Leave enough material above the vice jaw or V block to be able to fly or face cut it.  Would that get it accurate enough?
                   
                  I'm pretty new to this, so maybe there's a reason this won't work.  If so, somebody please speak up.  It's just what I had pictured in my head if I had to do it.  ..hhmm...actually, if I had to do it, I'd do it in the lathe :)
                   
                  Mike
                  in Gresham
                   
                   
                   
                  ----- Original Message -----
                  Sent: Friday, February 29, 2008 7:43 PM
                  Subject: [mill_drill] how true-up a disk cut from a bar?

                  I sliced a two cm thick slab from a round bar stock using a 4x6 band
                  saw that does not cut square to its table. So I have a disk whose ends
                  are not parallel to each other and are not at 90 degrees to the sides.
                  What steps do I take in a mill to true-up such a disk?

                • Norman Atkinson
                  One of my jobs was to do the top of a Stent tool and cutter grinder which is done to a finished diameter size of 11.5 ins by 2.5 wide and 7/8th thick- with 2
                  Message 8 of 13 , Mar 1, 2008
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                    One of my jobs was to do the top of a Stent tool and cutter grinder
                    which is done to a finished diameter size of 11.5" ins by 2.5" wide
                    and 7/8th thick- with 2 tee slots and clamps at each end at 9.5"!
                    I had a Myford which would not swing the casting and only a round
                    column mill drill. You start by flycutting the underneath bit to
                    clock the rest!

                    Obviously the speed could not be knocked down and I removed the top
                    casing on the pulleys- and did it all by hand- with a lathe tool in
                    the machine vise.

                    A simple tiddly little disc could have been pressure wedge clamped
                    onto the table, fly cut and flipped over and finished to size!

                    As old farts like me annoy and remark- 'Just wait, the really
                    exciting bits are yet to come!'

                    Have fun- it's only metal!

                    Norm
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