On 10 Mar 2011 01:13:51 GMT, "DoN. Nichols"
wrote:

[...]


I am not sure what engineering principles apply. Would an aluminum
shaft with a slip fit through a hole in the aluminum block suffice?

Likely to suffer galling.

Presumably a steel shaft would wear out the aluminum.

Actually -- a polished steel shaft would be a better bearing
with the aluminum housing than an al-al interface. keep it lubed, of
course.

OK, thanks, I don't have a clue about this stuff.

Would it be
better to use a steel shaft with bronze bushings? Ball-bearings seem a
bit of an overkill.

How much load forces are you expecting?

Drilling cross holes type of forces. However, if one could make it
more versatile by simple means, why not?

Maybe by the time I think this through I will find it expedient to get
a Taig headstock for $60+ and use it as a base for the project (a
common approach, apparently). However, I would still like to know what
is the correct approach if building from scratch.

Or -- perhaps get an old Unimat or Emco-Maier dividing head, if
you need no more than 60 divisions.

Of course -- the Unimat ones go for crazy money these days, if
you can find them on eBay at all. People are *collecting* these things
instead of using them. :-)

I saw a really neat little rotary table in the Proxxon catalog. It had
an integral chuck. I have not been able to find a dealer for it so
far.

But given the principles you outlined I might be able to knock
something together.

Michael Koblic,
Campbell River, BC