Re: screwless focuser

On 26 Jan, CAD_CAM_EDM_DRO@yahoogroups.com wrote:

> Imagine one end of a solid rod shaft supported by three bearings
> ...
> Ballendo

Hmm, another VERY good idea. I'd not heard of such a thing before.
Unfortunately, I may not be able to use it.

The problem is that the focuser body ( the fixed component that accepts
the balls ) needs to be as low profile as possible. One inch maximum
thickness is the goal, and allowing for the arc cut on the bottom ( so
as to mount it flush on the cylindrical telescope body ), even less than
that in one axis.

That one inch really doesn't leave a lot of room for three balls ...

On the other hand, it's such a neat idea, I think I'll try something
like that anyway, just to see what happens.

I'd like to thank everyone for their ideas. I'm going to CNC my
indexing head and try threading the tube on the mill that way first. If
it works, a simple G01 X1 Y1 should cut my thread. And if it doesn't
cut deep enough, a G01 X-1 Y-1 will.

But as this plan will only cut external threads, somewhere down the
road I'll also put a stepper or servo on the lathe spindle as well.

Frankly, I don't understand some of the .. resistance .. to the
spindle idea, ESPECIALLY from this group. Please don't misunderstand,
those who have proposed mechanical solutions, this is not a 'dis. But
being a longtime electronics guy and a newcomer to machining, the CNC
solution just naturally appeals to me.

I see no drawbacks to a CNC solution to thread cutting short of the
work involved. Moreover, the work is small - a new faceplate notched
for a timing belt and a bracket to mount a motor near the spindle is
all that's required.

I do see a several advantages, besides my lack of a QC gear box. No
more staring at the threading dial, no more "timing" the halfnut
closure, no more worrying about stopping the spindle in time when
moving right to left. Just a bit of code and some electronic magic.

Thanks again, all.

Alan


--

Alan Rothenbush | The Spartans do not ask the number of the
Academic Computing Services | enemy, only where they are.
Simon Fraser University |
Burnaby, B.C., Canada | Agix of Sparta