Re: [CAD_CAM_EDM_DRO] rack&pinion

> thumb their nose at rack-and-pinion, but.....

Not at all! Rack and pinion is used on many high-end router tables.

> Why? Is it because of higher backlash? If so, any qualitative
> indication?

The backlash can be eliminated by preloading paired gears, similar to
preloaded ballnuts.

Any redeeming factors? (like higher speed, easier

> construction, lower cost?)

Yes to all three. Ballscrews are limited by critical frequencies that
decrease as length increases. Even with a rotating nut configuration the
screw can resonate like a guitar string. A rack can be of any length
because it is continuously supported.

> How would one keep the "pinion" on the "rack"?

I saw a router table recently that had the rack ground into the back of the
linear rail. The gear straddled the rail between the carriages inside the
gantry. I can send you a picture if you are interested.

Doug