RE: Ballscrew installation issues

Roger -

I purchased the same ballscrew that McMaster sells, but directly from
Thompson, because I wanted the higher accuracy class. Thompson says they
are .631 ball circle x .200 pitch. I think the listing in the McMaster-Carr
catalog must be an approximation (why??). By the way, the higher accuracy
screws are only 50% premium for .001"/ft vs. the standard class .004"/ft.

Carlos Guillermo

> -----Original Message-----
> From: Roger Brower [mailto:rbrower@...]
> Sent: Sunday, February 20, 2000 8:29 AM
> To: CAD_CAM_EDM_DRO@onelist.com
> Subject: [CAD_CAM_EDM_DRO] Ballscrew installation issues
>
>
> From: Roger Brower <rbrower@...>
>
> stratton@... Wrote:
>
> Subject: Ballscrew installation issues
>
> >My plans for lathe conversion are
> progressing. snip...
> >What size (series/pitch) timing belts
> are people typically using?
>
> .2 pitch x 3/8 XL belts w/ 60 tooth
> steel & polycarbonate pulleys 1:1
> Berg and Stock Drive show more variety
> than McMaster-Carr, but the prices
> aren't listed in the catalogs.
>
> >With a .200 lead screw and a 200 step/r
> motor I need 2:1 reduction
> just to get steps of .001, but am
> planning on going for .0005 or
> .00033 if I use a 10 tooth driving a 60
> tooth.
>
> You may well end up using a half step
> driver for increased torque and reduced
> resonance reasons.
> A 200 step per rev motor is 400 discrete
> half steps per rev.
> Also note the McMaster 5/8 screws are
> 31/64" pitch; with 1:1 drive, I
> calculate: 1.8 deg per step motors, 200
> steps per rev, 400 steps per rev half
> step mode;
> 13/64" screw lead =(.203125 inch per
> rev, or 4.9230769 rev per inch)
> So: .203125 / 400 = ~1969(.2792) steps
> per inch for ~.0005 resolution.
>
> Am I in some kind of trouble with this
> odd number (vs 2000)?
> I know CNCPro can't use the decimal
> remainder (.2792) on steps per rev
> setting.
> I didn't want to gear it down and lose
> the travel speed potential or, God
> forbid, lose steps by trying to spin the
> motors too fast...
>