Re: [CAD_CAM_EDM_DRO] Re: Tapered Threads? Kim's TurboCNC codes

Kim Lux wrote:

>On Sat, 2003-11-01 at 14:12, rotarysmp wrote:
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>> Multiple encoder counts would add resolution to single pass
>>threads, but would then need a one/rev index count to allow multiple
>>passes along the same thread.
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>Multiple encoder counts are pretty much unnecessary. I've cut threads
>with TCNC that got 10 or more passes and they came out beautifully
>clean.
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Yes, for lathe threading, this is probably good enough for most work.
But, for the very similar rigid tapping on a mill, it is not good enough,
because the spindle must stop and reverse while the Z axis follows the
spindle rotation precisely. When the spindle shuts off and reverses,
the speed change per revolution can be very large, and the once-per-rev
pulse will not allow the Z axis to stay in close enough sync.

The other place where a single pulse/rev may fall down is in multi-start
threads. Theoretically, you can still do multi-start threads with a single
pulse, however. I don't know if TCNC supports that.

Jon