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Lathe work...internal thread cutting...***SORTED***

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  • Lathe work...internal thread cutting...***SORTED***

    So it seems some parts I ordered were never fully machined at the factory and I need some help to do a little skim to bring them to the correct size...

    It's the internal thread at the top of a fork tube...

    This thread has an unusual size 51mm, but the pitch is a standard 1.5mm...

    This won't be hard with the right sized lathe and correct cutting tool as it just needs a skim to cut the thread to full depth...

    I have two of them to be done and will provide the fork cap and a fork tube that is correct to assist with the job...

    So anybody got access to the required equipment and the skills and confidence to pull it off?

    Will pay in favours, alcohol or dollars...Oral Sex
    Last edited by Arwon; 12-02-2014, 06:26 AM.

  • #2
    I can get that done

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    • #3
      A quick job he says...
      Do you have any idea how hard it is to line up an existing thread when recutting on a lathe?

      I'd be keen to know who can do this.
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      • #4
        can't hire or borrow / buy said tap ??

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        • #5
          Originally posted by Shady7/8 View Post
          A quick job he says...
          Do you have any idea how hard it is to line up an existing thread when recutting on a lathe?

          I'd be keen to know who can do this.
          I'm a fitter machinist by trade, so yes...

          - - - Updated - - -

          Originally posted by t bone View Post
          can't hire or borrow / buy said tap ??
          M51 x 1.5mm...not a standard thread...

          You can get an M52 x 1.5mm...

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          • #6
            Originally posted by Shady7/8 View Post
            A quick job he says...
            Do you have any idea how hard it is to line up an existing thread when recutting on a lathe?

            I'd be keen to know who can do this.
            I was thinking the same thing, lining up an external thread would be tricky, internal would be even worse.
            I suppose you could engage the screw cutting feed with the tool off the work, stop the lathe then move the work so the thread lines up. But this would assume the work was held in a 3 jaw chuck and when you re-clamp it it's unlikely to be running perfectly true.....tricky work....very tricky work....unless you happen to have access to a 51x1.5mm tap.
            Originally posted by mekon
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            • #7
              It actually isn't that hard to line up...

              Set lathe up to cut correct pitch with tool in...

              Engage lead screw, do not disengage at any time...

              Bring the tool into the internal area, but not out at the cutting diameter...

              Use cross slide and compound slide to bring tool out to the correct diameter and in line with pitch, do this without the lathe turning...

              Very light initial cut and check your alignment and adjust...

              When cutting in take note of the measurement on your cross slide...

              Reverse lathe to bring tool back out...

              Add a little more cut, in again...

              Rinse and repeat...

              If I had access to the equipment I would do it myself...

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              • #8
                ^^ this, done it a hundred times, compound slide set at the 30؛ tooth angle gives you X adjustment with a Y artefact which can be removed with the cross slide.

                The trick is finding a lathe and chuck with a 55mm throat that's sitting there doing nothing - Rich, any time you want to swap for 18mm forks you're welcome to come and use my gear.
                "Once upon a time we would obey in public, but in private we would be cynical; today, we announce cynicism, but in private we obey."

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                • #9
                  If that is the case, try these guys, ask for Graeme;

                  CNC Machining, Milling & Wire Cutting Perth | Machine Shop, 3D CAD & CAM Design | Overload Machining Services
                  They hung a sign up in our town "If you live it up, you won't live it down"-Tom Waits

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                  • #10
                    Yep, need a minimum of ~60mm bore down the spindle...

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                    • #11
                      I expect if I take it to a machine shop and pay normal Perth machining rates I will be able to buy new tubes cheaper...

                      Hence I need someone to do a mates rates job...

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                      • #12
                        pm MattPack. I know he has a lathe in his shop but not sure how big. he does a lot of odd/custom jobs on bikes so may be able to assist.

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                        • #13
                          yeah not especially hard to do...

                          have you thought about just sticking it in a lathe and using a thread file to just tickle it out a bit?

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                          • #14
                            also, because you would only have to spin it slow, you could grip on the end in a small lathe with a steady attachment..
                            I'm sure it would be ok if only a little amount of meat has to come out...

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                            • #15
                              Little lathes will probably struggle with bed length to fit the stanchion in there, too. Plus, even with teflon or brass sliders on the steady, I'd be too shit scared of scoring the chrome even if it was at the top where the triple grabs on.
                              "Once upon a time we would obey in public, but in private we would be cynical; today, we announce cynicism, but in private we obey."

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