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

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  • Rick Kruger
    Looks like a good solution for thin pieces. I was thinking 2 cm was thick enough to hold in a 3- or 4-jaw chuck, but if not the superglue trick looks like it
    Message 1 of 13 , Feb 29 10:32 PM
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      Looks like a good solution for thin pieces. I was thinking 2 cm was
      thick enough to hold in a 3- or 4-jaw chuck, but if not the superglue
      trick looks like it would work. 2 cm is just over 3/4". All of my
      5" & 6" chucks, the jaw steps are about 3/8", so there shouldn't be
      any issue about not being able to hold that part in a chuck for turning.

      I was working on a set of parts for a friend the other day, where I
      was facing 1" thick blanks that were about 3" in dia. on a large
      lathe (16" swing). Using the 10" 3-jaw chuck on the lathe, I would
      grab the part by the last two teeth of the lathe chuck and close the
      jaws until they just grabbed and then backed them off just a touch,
      so the part would jiggle. Then I held the part and jiggled it as I
      tightened the chuck. Sometimes I had to do this a couple/few times
      to get the OD of the blank evenly gripped by all three jaws. This
      got the blank fairly well aligned with the jaws using the OD as the
      reference surface. Then facing was done. Turned the part around and
      repeated. This method works okay when the two faces don't have to be
      parallel and don't have to be highly perpendicular to the OD. My
      thought is that it might get the part held somewhat close to
      perpendicular with the OD so the first face could be turned, and then
      turn it around and seat the turned face against the jaw flats for
      turning of the second face.

      We still don't know if this will work for John, as we don't know if
      he has a lathe. If he only has a mill, he might have to superglue it
      to his mill table, mill one side and turn it over. Still doesn't do
      anything for making the faces perpendicular to the bar stock sides.

      Rick

      At 09:44 PM 2/29/2008, you wrote:

      >Rick, I agree with your comments, but I have an off the wall idea.
      >Check www.youtube.com and look for the superglue chuck. it maybe
      >listed under Sherline lathe. You can mount a flat plate to your
      >table. Pick one side. Glue it down and machine, then remove following
      >directions on the video.
      >
      >Frank
      >
      >
      >--- In mill_drill@yahoogroups.com, Rick Kruger <krugerr@...> wrote:
      > >
      > > You didn't say what diameter the bar stock is and whether the bar
      > > stock OD is finish size or you have machining stock. If your
      > > existing OD is too close to finish size, I probably don't have any
      > > good ideas for you. If you have machining stock on the OD and have
      >a
      > > way of gripping later for turning the OD, you probably are best off
      > > grabbing the OD in a chuck and facing the slabs square. That is,
      >if
      > > there is enough stock to machine off the non-parallelism. If not,
      > > you may just have to saw off thicker pieces and do the facing on
      >new pieces.
      > >
      > > This is definitely a learning point about getting to know your band
      > > saw and how to blank off material that gives you enough stock to
      >work
      > > with. When my HF 4x6 band saw was new, it cut much more square
      >than
      > > it does now, even with new blades. I just compensate to make sure
      >I
      > > cut off thick enough pieces so that I can square them up during
      >machining.
      > >
      > > You also didn't say that you have a lathe (since this is a mill
      > > group). If you don't, you probably will have to clamp the part on
      > > your mill table and mill the part parallel. Same caveats as facing
      > > as far as having enough stock to do that.
      > >
      > > Rick
      > >
      > > At 07:43 PM 2/29/2008, you 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?
    • 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 2 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 3 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 4 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 5 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 6 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 7 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 8 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 9 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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