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Cutting gear hobbed stick

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  • Cutting gear hobbed stick

    If I had a 18 tooth module 0.3. hobbed pinion gear 'stick' say 7" long, how would I cut them approximately .268" long (they need a 3mm bore too) and how many should I be able to get? I haven't a clue how to accomplish this. Obviously I don't want to damage the hobbed 'stick'.
    Last edited by Smokedaddy; 05-15-2018, 03:22 PM.

  • #2
    Lathe, soft jaws, and a parting tool. Drill and ream for the 3mm hole about 1" deep, and part a couple off, rinse repeat. Get friendly with some small needle files or a wire wheel for deburring depending on tolerances/finish required.

    7" long with a .125" wide parting tool will theoretically net you 17 whole pieces @0.268" thick. You will need to hold onto it somehow so you'll probably get less and have a bit of waste leftover.

    You could get a lot more if you knew somebody with a wire edm, and wanted a nice gravy job of "slicing" them off for you. Deburring would be nicer too.

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    • #3
      I'd grind an extremely thin parting tool. I'd be concerned a standard width tool of say 1/8 on a .200 dia pinion would apply a lot of force on tiny teeth that would beat the crap out of them. run it quickly with a slow steady infeed. even parting round bar of small diameter is easier with thin tool. After parting, while still spinning, I'd touch the edge with a file so there was nothing proud of the dia (at at least one end of the part) so it could be put into a collet for drill/ream. The problem continuous dill/part is if the drill starts to wander (it will) it will keep wandering unless you keep facing/spot drilling
      .

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      • #4
        Originally posted by Mcgyver View Post
        I'd grind an extremely thin parting tool. I'd be concerned a standard width tool of say 1/8 on a .200 dia pinion would apply a lot of force on tiny teeth that would beat the crap out of them. run it quickly with a slow steady infeed. even parting round bar of small diameter is easier with thin tool. After parting, while still spinning, I'd touch the edge with a file so there was nothing proud of the dia (at at least one end of the part) so it could be put into a collet for drill/ream. The problem continuous dill/part is if the drill starts to wander (it will) it will keep wandering unless you keep facing/spot drilling
        find a very thin circular saw blade for wood and regrind the end for less relief, also need to regrind the face square to the blade. should take about 2 minutes with a diamond hone. when/if the carbide breaks, rotate it to the new edge. probably limited to a 4.5" blade unless you hang it off the side of the compound.

        of course you can cut the blades into pie shaped pieces, but the heat of cutting it may warp the blade.

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        • #5
          Originally posted by johansen View Post
          find a very thin circular saw blade for wood and regrind the end for less relief, also need to regrind the face square to the blade. should take about 2 minutes with a diamond hone. when/if the carbide breaks, rotate it to the new edge. probably limited to a 4.5" blade unless you hang it off the side of the compound.

          of course you can cut the blades into pie shaped pieces, but the heat of cutting it may warp the blade.
          I don't see an advantage in carbide for this. Far easier imo, at least what I do, is just grab a hss blank and grind the parting tool end. I just checked some and 30-40 thou looks about right for the width. Of course there is always more than that one way to come at it, but thats how i'd do it.
          Last edited by Mcgyver; 05-15-2018, 06:12 PM.
          .

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          • #6
            I've made an holder to take a hss hacksaw blade as parting tool. It works ok.
            Helder Ferreira
            Setubal, Portugal

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            • #7
              I haven't tried this yet, but tests with other pieces seem to indicate it will work. When you grind your parting tool, do so with the face at an angle so there's a point on the side of the gear you want to keep. This should keep your teeth in much better shape as you part the piece off.

              Also, take a look at this thread:
              https://groups.io/g/RepowerAndRegear.../8786805#15654

              Where'd you get the gear stick?

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              • #8
                Likely the gear is not hobbed but drawn through a multistage die. They call it pinion wire I believe.

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                • #9
                  Come on guys look it up if you don't know.

                  The gears are approximately 6.4 mm in diameter!

                  Cut them off with a tool post mount Dremel

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                  • #10
                    Originally posted by bob_s View Post
                    Come on guys look it up if you don't know.

                    The gears are approximately 6.4 mm in diameter!

                    Cut them off with a tool post mount Dremel
                    I was told the sticks are hobbed. I like that idea. Any more specific suggestions are welcome. I do have a couple of Dremel(s). Guess I'd have to devise some sort of holder for the Dremel. I'm not sure what the material will be yet, more than likely Delrin. Lathe is a EMCO Mentor V10.

                    -SD:
                    Last edited by Smokedaddy; 05-15-2018, 09:55 PM.

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