Re: [CAD_CAM_EDM_DRO] Spindle question again . First post was as clear as mud

tig415 wrote:

>Sorry about that
>Lets try again.
>The wood shop next door has a commercial cnc router with a high
>speed spindle motor on it. It has a series of air lines running to
>the spindle and I was curious if these were for cooling the
>bearings and if so are they special bearings.
> I think Jons post pretty much answered it though.
>
>

Probably not. The most common setup for mid-range speeds (10,000 -
25,000 RPM,
at least) is oil mist cooling. Dry air, with a fine mist of very light
oil is sprayed
right into bearings that have no shields or seals, at least on the
bearing races
themselves. The expanding air cools the bearings, and the small amount
of oil
cuts down on wear without creating much heat. I got an Danly/Onsrud 5 Hp
15,000 RPM router spindle on eBay that used this setup. I didn't check
it out
carefully, it was a 75 Lb monster, and I had to go and sell it on to someone
else. I had no idea the thing was that heavy!

Air bearings are much more common above 50,000 RPM. Some dental drills use
air bearings at 300,000 RPM.

Jon