Re: [CAD_CAM_EDM_DRO] Building a small 4th axis

Hi Tony,

Yes! I recall seeing that photo before. Certainly works! That I can
do in the mill, with the CNC rotary table.

Does sound like the gear head Vextra's would be slow to cut a thread,
but I'm in no hurry. Another thought was to drive the 90V Sherline
motor with a Gecko G340 servo drive. Even at lower voltages, that could
be useful.

Alan KM6VV


Tony Jeffree wrote:

>
> At 11:15 04/06/2003 -0700, you wrote:
> >Not exactly the same thread, but I like these "symbiotic" ideas! A few
> >days ago I saw a Sherline rotary table w/stepper being used to drive the
> >Sherline spindle on a lathe for threading (and what not). Probably on
> >Bryan's web site. Seems to me that a gearhead stepper motor (some
> >Vextra's I picked up come to mind) could be used quite easily the same
> >way. This would allow any CNC controller program to turn the spindle in
> >direct ratio to the lead screw, which is what's wanted. The other way
> >is to add an encoder to the spindle, "Sync" and drive a leadscrew off of
> >that via software.
>
> Hi Alan -
>
> There was a series of articles a few years back in Model Engineers'
> Workshop magazine, describing a CNC-ed Taig lathe. The guy had indeed
> managed to do threading by stepper-driving the headstock via a reduction
> drive, and driving the saddle traverse & headstock motors at appropriate
> rates to generate the right lead per rev. Problem he described was that,
> because the power available from the stepper on the headstock was
> significantly lower than a conventional spindle motor, he had to use low
> speeds (to maximise the stepper torque) & hence cutting any significant
> thread length was interminably slow. Perfectly possible though.
>
> I have done a similar thing on my mill - using a rotary axis to rotatre the
> part to be threaded, and a 60-degree V-tip engravibg cutter to cut the
> threads. See the second-from-last photo on this page:
>
> http://www.jeffree.co.uk/Pages/divheadmk2.html
>
> Took a while, but generated a great thread!
>
> Regards,
> Tony
>
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