"Pete Keillor" wrote in message
...
On Thu, 7 Aug 2014 11:19:57 -0400, "Carl Ijames"
wrote:

The pulley is aluminum and presumably the set screws will be some
kind of
steel alloy so they are three times the density of the aluminum,
which
should make up for the "missing" volume from the threads and hex key
socket.
They might even be too heavy. Considering how close they are to the
shaft,
I bet the balance will be pretty much dead on with just the two
plain set
screws. If you set up the knife edges it would be interesting to
check the
pulley before you drill and tap the set screw holes, just to make
sure it is
dead on, and then you could see if the set screws change anything.

-----
Regards,
Carl Ijames

"DoN. Nichols" wrote in message
...

On 2014-08-06, Pete Keillor wrote:
I'm to the point of turning the drive wheel for the belt grinder
I'm
building for my son. It'll be 6061 Al, 6" dia. x 2" wide, running
on
a 3/4" keyed shaft, and turn up to 3800 rpm. I figure I'll put a
setscrew on the key and another at 90 deg., which will require
drilling from the circumference. I can drill holes opposite to
help
balance.

Any suggestions on how to balance this for a hobbyist? I'm not
buying
a balancer, but could build something. Or just spin it up and see
how
it does? Thanks.

Hmmm ... if you make the screw enough bigger (and perhaps an
Allen head cap screw (if you have hollow ends and hubs within that),
you could compensate for the mass missing from the drum surface.
Then
no need to drill an extra hole opposite. Maybe add a nut for
locking
and extra mass, too.

Enjoy,
DoN.

Thanks to everybody for the suggestions. I'm out of town and didn't
have access for a while. It's the wife's business junket, but
spouses
were invited, so who in their right minds wouldn't get out of Texas
in
August to Park City, Utah. Got in some very pleasant hiking.

I now plan to use the knife edge idea originally mentioned by Ed,
then
depending maybe add extra set screws if needed or drill opposite.
Probably just spin it first, but the disc would be near the mill
spindle on the 3/4" shaft which is pretty short, 10" back through
the
collet. No worries about whipping. If it seems smooth enough,
that'll be it. The idler and contact wheels should not be a problem
because they run on their own bearings and are uniform.

Pete Keillor

Does an unbalanced flycutter or boring head make your mill vibrate?
-jsw