Re: [CAD_CAM_EDM_DRO] screwless focuser was Re: re:Re: Re: Is this too nuts to consider ?

ballendo@... wrote:

> So if we INTENTIONALLY 'skew' the bearings at the pitch angle of
> the "thread" we want to create, the shaft will move longitudinally
> (in and out, toward and away from the bearings) JUST AS IF the shaft
> WERE threaded!

Totally valid concept, and commercially available. Also relatively easy
to do in the garage shop. I made one up as an experiment for a low-cost
substitute for ball screws a couple years ago. Very sensitive to dirt
and grit on the shaft, but very very smooth when everything is clean.

I would only add that with the bearing skewed, there is no longer line
contact, or at least it's diminished greatly. Running hard bearings
against a soft aluminum tube will probably chew things up. For a scope,
perhaps delrin rollers might work better.

Jon