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turning discontinuous work

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  • turning discontinuous work

    I would like to modify a motorcycle cush drive for a custom wheel swap...I need to cut down the drive dogs. Obviously a mill would be best, but mine is not running yet.

    Can I turn this in the lathe? Each drive dog is going to strike the tool, and I'm worried that this will damage the tool or my machine.

    The machine is a Southbend 10" using 1/4" tooling...far from the ultimate in rigidity...would this be considered abuse? The material is aluminum (cast I'm pretty sure).

    I hope I'm clear describing the problem...if not, consider a square and each corner smacking the tool as the work turns. Only in this case there are five drive dogs arranged symmetrically around about a 5 inch diameter circle so my tool will be smacked five times per rev as I face the dogs down to proper length.

    Thanks for your time and help.

  • #2
    HSS Tooling works well for this. Small starting cuts. HSS is good for intermittent cuts where carbide will break immediately.

    Also watch the overhang on your compound rest. This is a major factor in intermittent work cutting. Imagine a diving board being bounced each time the work hits the tool. No overhang, in fact back it off a bit to put the tool more over the pivot.

    Larger nose radius on the HSS tool to start - say 1/32 inch or more. Also neutral rake as positive will catch. I have actually taken a neutral grind thread tool, and have put as much as a .050 rad tip on it or better for this stuff.

    I have to do stuff like this too much, this is what has worked best for me.


    • #3
      For home use use HSS or T-15 on interrupted cuts.


      Generally I would concur with not using carbide - in particular the brazed tools and low technology inserts. But I just wanted to remind you - with all due respect - that some truly incredible tools exist today that were non-existant a few years ago. Even Cermets have better IC capabilities due to the use of Silicon Nitride "whiskers" as reinforcements - much like the glass fibre or cloth in fibreglass composites. It is expected that a super tough carbide grade specifically for interupted cuts will be out in the next few years - test show this stuff to be almost as tough as T-15 and it will be aimed at the home market as a replacement for HSS.

      It is indeed facinating to watch one discovery in technology ripple through all the others - we live in interesting times.

      [This message has been edited by Thrud (edited 05-21-2002).]