On 2011-02-21, Lloyd E. Sponenburgh lloydspinsidemindspring.com wrote:
"Pete C." fired this volley in news:4d62907a$0$1855
:

For a servo
connection you need to use a "hard" connection. Note that in a manual
mill, the feedback from the dial or from a scale is after the handle
clutch and thus the handle clutch backlash is not a factor.


So long as you mean "tight", not "hard" I agree.

A lot of stepper-drive machines use a Lovejoy coupling between motor and
ball screw, with a very tight (even very tightly compressed) spider.

My servo motor driven rotary table (4th axis) is based on this kind of
coupling.

As for the knee, if, say, I have one degree of "slop", which is a lot,
this amounts to roughly 1/5"*1/360 = 0.0006" of accuracy. Remember
that 360 degree turn is only 1/5 of an inch or something like that.

I am not building a space station here, so 0.0006" extra inaccuracy, I
can live with. (and deal with programmatically)

i