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  • Spline broach

    I'd like to make some motorcycle shift lever components requiring a round spline broach in the neighborhood of .5" x 30 V shaped splines.

    I don't begrudge broach manufacturers what they ask for such products but I'm not interested in going into production to pay for them so;
    how would I make one please?
    Len

  • #2
    Originally posted by QSIMDO View Post
    I'd like to make some motorcycle shift lever components requiring a round spline broach in the neighborhood of .5" x 30 V shaped splines.

    I don't begrudge broach manufacturers what they ask for such products but I'm not interested in going into production to pay for them so;
    how would I make one please?
    What machines and fixtures do you have at your disposal?

    Comment


    • #3
      As Wyop asked, what machines?

      On lathe you could single-tooth slot it with a profile tool much the same as cutting a keyway, by using the carriage to advance the tool through the work, in a mill you could do the same using the quill. You'd need a way to index/divide the work position to each spline, e.g. if you have an accessible gear on lathe spindle or a rotary table on the mill. If you have a shaper, you're 3/4 there already!

      IF you are likely to make more than one you could look at rotary broaching, either in lathe or mill, but you'd have to make a suitable broaching bit to reproduce the splines, which would be as much work as cutting the splines... Once you have the rotary broach you'll be able to do pretty much anything you can make the bits for though: splines, square drives, hex sockets, torx, anything with rotational symmetry!

      I'm assuming it's the internal spline you want to make, as the splined shaft is going to be part of the bike's gearbox?

      Dave H. (the other one)
      Rules are for the obedience of fools, and the guidance of wise men.

      Holbrook Model C Number 13 lathe, Testa 2U universal mill, bikes and tools

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      • #4
        It sounds like a job for a shaper and dividing head. Make a block the size required for clamp bolt/screw etc. then weld lever to it.

        Comment


        • #5
          Originally posted by Hopefuldave View Post
          As Wyop asked, what machines?

          On lathe you could single-tooth slot it with a profile tool much the same as cutting a keyway, by using the carriage to advance the tool through the work, in a mill you could do the same using the quill. You'd need a way to index/divide the work position to each spline, e.g. if you have an accessible gear on lathe spindle or a rotary table on the mill. If you have a shaper, you're 3/4 there already!

          IF you are likely to make more than one you could look at rotary broaching, either in lathe or mill, but you'd have to make a suitable broaching bit to reproduce the splines, which would be as much work as cutting the splines... Once you have the rotary broach you'll be able to do pretty much anything you can make the bits for though: splines, square drives, hex sockets, torx, anything with rotational symmetry!

          I'm assuming it's the internal spline you want to make, as the splined shaft is going to be part of the bike's gearbox?

          Dave H. (the other one)
          I have pretty much everything BUT a shaper!

          I'm intrigued with rotary broaching because of the various style bits one could craft and the suitability for both lathe and milling machine.
          Initially, though, I was thinking of a broach for use in the press and configured as a rotary bit with a concave face but I got stalled on
          how to stabilize it while pressing through the hole.
          Perhaps supported on the outside with a piece of thick wall DOM?
          Len

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          • #6
            I've not used a spline broach so take it with a grain of salt, but I've used lots of broaches and have made a few. A single key broach takes a fair bit of force, I'd think the very wide cutting area of a full spline broach would require both a very long broach so you a get small chip per tooth, and probably special machine capable of a long accurate stroke. Accurate as in no side forces. Big broaching is often done by pulling, that might be way to go.

            The alternative would be a DIY single key type broach you index around the ID. Still, I think I would look at doing it in the mill or lathe, with a single tool, i.e the old shaping trick. Making a broach is a lot of work, i've only done it when I needed a square or hex, but wouldn't think its worth it if the shaping solution would get it done. Or its a reason to make a rotary broach.

            I'd also look at having it done, if you could find the shop with the tools already. It wouldn't take long so shouldn't cost much. There probably was a time I'd frowned on such practical solutions, like there's some code of do it yourself or you're not worthy, but I've such a large heap of projects i really like the idea of reducing it rather than piling more on it
            Last edited by Mcgyver; 06-26-2019, 12:36 PM.
            .

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            • #7
              I came up with a possible solution to this years ago (when I was actively racing and needing spare parts), although never got a chance to try it out, BUT, I think it would work. I made lots of rearset brackets and pegs, but never crashed my way through my spare supply of shift levers so I never had to make one and try it out.

              First you need a junk shift shaft to use as your "broach" (but with a good spline). Grind some back clearance off of the spline, and grind all but 3 teeth away to a smaller dia than the minor diameter. Then grind in a cutting edge on the face. Now to use it you would first drill a start hole at the minor dia, and then move off center in a mill, and manually plunge the "cutter" (shift shaft turned broach cut down and held in a collet or chuck) with the quill, moving out radially until you've come back to centerline. If you've got a dro this is easy. Then you rotate the tool using the extra 2 teeth to index from the 3 you just cut, and keep plunging out the remaining spline teeth until you're done. This should go pretty quick in aluminum.

              I've done plunge broaching before to pick out square corners quite a few times, but never like this so I'm only "theorizing" that it works, but have no reason to believe it won't for the intended purpose. I use a small bungee to hold the spindle brake to hold the cutter rotation. Shift shafts have a clamp screw anyway so "perfection" isn't really required. Might be a cheap way to try it if you've got a spare shift shaft lying around
              Last edited by Dan Dubeau; 06-26-2019, 04:05 PM.

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              • #8
                hot broach it. Will need a helper. Junk shaft with good splines,a flat piece of steel 3/8 to 1/2 in thick, some way to hold it. Drill a hole that the shaft will fall through in the steel. On the shaft, turn the unsplined end smaller than the minor diam. of the spline. Drill the work to minor size, heat to red hot place over hole, have helper place splined end of shaft over hole in steel and hit with big hammer. drive all the way through and out the other side. Cut slot if needed drive wedge in slot to expand to fit shaft then drill and tap.

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                • #9
                  DD in post 7 has it.

                  However, if "broaching" into aluminium, even simpler.
                  I made many Meriden Triumph gear levers in the old days out of aluminium.
                  The broach was just the original multi-spline shift shaft.
                  Correct sized hole, gear lube, and a 15 ton press.
                  Drill, tap and slot for a pinch bolt, bish bosh job was a good 'un.
                  In fact my current Triumph has the same lever i made in 1994 still on it.
                  Doubt the above will work in steel nor SS, but that's too heavy for bikes right?

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                  • #10
                    Have you seen this?

                    https://www.youtube.com/watch?v=MYI1slVGziU
                    I just need one more tool,just one!

                    Comment


                    • #11
                      Originally posted by thaiguzzi View Post
                      DD in post 7 has it.

                      However, if "broaching" into aluminium, even simpler.
                      I made many Meriden Triumph gear levers in the old days out of aluminium.
                      The broach was just the original multi-spline shift shaft.
                      Correct sized hole, gear lube, and a 15 ton press.
                      Drill, tap and slot for a pinch bolt, bish bosh job was a good 'un.
                      In fact my current Triumph has the same lever i made in 1994 still on it.
                      Doubt the above will work in steel nor SS, but that's too heavy for bikes right?
                      Right, I do like Dan's method as well.
                      I would occasionally have need for use on firmer materials though...what can I say, I LIKE stainless!
                      I just make it thin enough...still, far from MotoGP I'm building
                      Len

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                      • #12
                        Originally posted by QSIMDO View Post
                        ...still, far from MotoGP I'm building
                        but beautiful things you are making, hmm?



                        (sorry, Yoda moment there)

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                        • #13
                          Originally posted by mattthemuppet View Post
                          but beautiful things you are making, hmm?



                          (sorry, Yoda moment there)
                          Don't apologize, it had to be said.
                          Len

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