Re: Cheap 56,000RPM milling upgrade (not a dremel :)

--- In CAD_CAM_EDM_DRO@yahoogroups.com, Jon Elson <elson@p...> wrote:

> cnc_4_me wrote:
> >What would happen if you do not turn on the air and then operate

the

> >motor. Will it run in a derated mode.
> >
> >
> The bearings will burn up. Since this is a $6000 spindle, I sure

don't

> want to find out.
> Actually, I had an air hose blow off while it was running, and it

kept

> spinning just fine
> until that hole was completed, then I shut it off. The thrust

bearing

> won't work worth
> a darn without air, but the radial bearings seem to work well, as

their

> design makes
> them somewhat hydrodynamic.
>
> To be totally clear, these are not air-cooled bearings. The

spindle

> flies on a cushion
> of air, within a bearing that is a VERY close fit to the journal.

Air

> is injected
> from a bunch of radial holes in the bearing. I think the bearing
> clearance is in
> the region of .0002" per side. So, these bearings crash every time

the

> air is turned
> off.
>
> Jon

Good post Jon. I was looking for a answer that would give me a clue
to its construction. I asked the question rather badly but you still
gave me a good answer.

P.S. My jaw dropped when you said $6000.00 spindle. I suspect they
are not using ceramic roller skate bearings.


Wally