Re: [CAD_CAM_EDM_DRO] 4th axis rotary table - suggestions?

Howdy All! I have an 8" Palmgren rotary table that I have been looking
at as a 4th axis, {actually 4th, 5th, & 6th axes, it is an X-Y-Rotary
table} and it has very little backlash. Not having done any rigorous
measurement*, except with the Mk I eyeball, it looks like a .001"
backlash. From what I've gathered from Rec.Crafts.Metalworking, my
Bridgeport will have that much or more slop to begin with. I would be
surprised that a good quality standard table would have an excessive
amount of slop.

*How's this as a plan to measure the backlash: Stick a front-surface
mirror on the rotary table, aim a laser pointer at the mirror and mark
that place on the wall 10' away. Crank the handwheel back and forth 10
times through 10 or 15 degrees and mark the resting point of the laser
dot. The difference between the start and end points divided by 10
should be the backlash since the error I induce trying to hit the mark
at both ends of the swing sould be random and would cancel out.


"David M. Munro" wrote:

> Hello,
>
> For my BP cnc conversion, I was planning to fit a 4th servo to a
> standard
> (but good quality) rotary table. It has been pointed out to me that
> the
> backlash on a manual rotary table in going to do me in,

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