On Tue, 26 Nov 2013 00:15:06 -0600, Tim Wescott
wrote:

On Mon, 25 Nov 2013 18:20:47 -0800, etpm wrote:

I've been looking at the brushless motors used for RC planes and the
like. They are amazingly powerful for their size. And they really spin
up fast! One web site has kits you can buy to wind your own armatures.
Anyway, I have been wanting a rotary tool that is a cross between a
Dremel and an air powered tool I have. Something with an OD of about 1
inch. Like a Foredom handpiece. Faster than any of my Dremels but slower
than my small air powered hanpiece that spins at 80,000 rpm. So I'm
thinking one of the "inrunner" type motors might work. At 80,000 rpm the
surface speed is about 2600 SFPM. Even though the speed drops quickly as
soon as the rotary tool contacts the work the speed is still too high
for carbide on steel and the burrs and rotary files dull quickly, which
makes them cut slower. On the other hand, the Dremel and Foredom rotary
tools are too slow and this ends up costing time too. Something that
spins about 40,000 rpm and maintains that speed along with the smaller
diameter would be great. In fact, a tool that was .75 or even .625
diameter would be even better. I have a dental handpiece that I use for
some delicate work and it is just under .5 diameter and is very easy to
hold because of the small diameter. If I could build an electric rotary
tool with the torque of a Dremel, 40,000 rpm, and 1/2 inch in diameter I
would be very happy. Even one that matched the Dremel torque and speed
specs but was 5/8 or 1/2 inch diameter would please me greatly. So,
anyone here play with brushless RC motors?
Thanks,
Eric,

Not for what you're contemplating -- but I do have a couple of RC planes
that I fly with them.

It may work. I'd use an ESC with a helicopter "governor" mode for steady
speed. Make sure you have lots of fan cooling -- those motors get light
in part by being designed for steady airflow (they're AIRPLANE motors!!
). I wouldn't count on the motor bearings to hold up to much side-force,
so you'll have to provide support against that.
I of course would only be subjecting the motor to torque forces.
Robust ball bearings are needed to support the cutting tool. I didn't
know about the ESC "governor mode". Thanks for that.
Eric