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Re: [taigtools] Lathe Cross slide backlash

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  • Tony Jeffree
    Paul - See my posts earlier in this thread. You are right about the cross-slide backlash, and right about most plain turning operations, but if you were
    Message 1 of 30 , Apr 4, 2013
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      Paul -

      See my posts earlier in this thread.

      You are right about the cross-slide backlash, and right about most plain
      turning operations, but if you were cutting a contour where the tool
      changes from cutting on one flank to cutting on the other (e.g., a chess
      piece), then although the Z travel would be all in one direction, the
      cutting force on the tool would change directions as the cutting action
      changes flanks. At the point where the direction of the cutting force
      reverses, the direction in which any leadscrew backlash is taken up also
      reverses. This is exactly the same problem you get with a milling machine
      when you try to mill a circular path and you have backlash in the X and/or
      Y feeds. The reason that it is not a problem with the cross slide is that
      (for obvious reasons) you never switch from cutting on the nose of the tool
      to cutting on its back end.

      Regards,
      Tony


      On 3 April 2013 18:21, Paul J. Ste. Marie <taig@...> wrote:

      > On 4/1/2013 10:03 AM, Ron Thompson wrote:
      > > CNC is capable of contour cuts, like in a chess pawn. So, yes, backlash
      > > can be a problem.
      >
      > Isn't the force from the lathe always pushing the tool away from the
      > work? I've never noticed any tendency for the tool to dig into the work
      > running by hand, although I haven't turned any brass on the lathe.
      >
      > Typical lathe tools only cut one way in Z, so lead screw backlash isn't
      > usually going to be an issue, either.
      >
      >
      >
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    • Paul J. Ste. Marie
      ... How does that work? Tool with zero side rake? IIRC that s how Taig grinds their round v-nose tool, but my experiences with that tool have been less than
      Message 2 of 30 , Apr 5, 2013
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        On 4/4/2013 5:06 AM, Tony Jeffree wrote:
        > if you were cutting a contour where the tool
        > changes from cutting on one flank to cutting on the other (e.g., a chess
        > piece), then although the Z travel would be all in one direction, the
        > cutting force on the tool would change directions as the cutting action
        > changes flanks.

        How does that work? Tool with zero side rake? IIRC that's how Taig
        grinds their round v-nose tool, but my experiences with that tool have
        been less than stellar.

        I haven't done any CNC on the lathe, but for something like the little
        flange under the head of a chess piece I'd expect to do two passes, one
        from the right, a second from the left, and switch out tools in between.
      • Tony Jeffree
        Use a V tool (e.g., a thread cutting tool). Regards, Tony ... [Non-text portions of this message have been removed]
        Message 3 of 30 , Apr 5, 2013
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          Use a V tool (e.g., a thread cutting tool).

          Regards,
          Tony


          On 5 April 2013 18:44, Paul J. Ste. Marie <taig@...> wrote:

          > On 4/4/2013 5:06 AM, Tony Jeffree wrote:
          > > if you were cutting a contour where the tool
          > > changes from cutting on one flank to cutting on the other (e.g., a chess
          > > piece), then although the Z travel would be all in one direction, the
          > > cutting force on the tool would change directions as the cutting action
          > > changes flanks.
          >
          > How does that work? Tool with zero side rake? IIRC that's how Taig
          > grinds their round v-nose tool, but my experiences with that tool have
          > been less than stellar.
          >
          > I haven't done any CNC on the lathe, but for something like the little
          > flange under the head of a chess piece I'd expect to do two passes, one
          > from the right, a second from the left, and switch out tools in between.
          >
          >
          >
          > ------------------------------------
          >
          > To Post a message, send it to:
          > taigtools@yahoogroups.com
          >
          > To Unsubscribe, send a blank message to:
          > taigtools-unsubscribe@yahoogroups.com
          >
          > Let the chips fly!
          > Yahoo! Groups Links
          >
          >
          >
          >


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