In article
,
Stanley Schaefer wrote:

On Mar 5, 8:25*pm, "Wild_Bill" wrote:
There doesn't seem to be a good reason for the pins. Maybe the only way to
find out what problem (real or imagined) Rockwell designers thought they
were addressing, would be to find some advertising literature from the time
when this type of "feature" was introduced.

Putting a thru hole that size in a 1/2" shaft doesn't seem reasonable to me,
but I assume someone thought it would be a good idea.

If there were wrench flats (or pin spanner holes) on the inner wheel flanges
to fit a wrench when removing and replacing the shaft nuts, I could see some
perceived practical use for the pins, but then only really useful if the
nuts were nylock types (any type of locking nut is not actually required for
mounting grinding wheels), because grinding wheel nuts don't require
significant torque to make the mounting secure.

I've seen used bench grinder arbor threads that have been chewed up by
someone using a plier on them, apparently by someone not smart enough to
figure out the right direction to turn the nuts, or not confident in having
the nuts just snug enough to firmly secure the grinding wheel.

I've also seen wheels with significant gouges in them, so if an accidental
jam on one side caused the motor's rotor to stop, it's possible the other
wheel could continue to rotate, but that's still not likely to unscrew the
nut from the arbor threads.

--
WB
.........

"Joseph Gwinn" wrote in message

...



I recently acquired a somewhat rusty used Rockwell 6" bench grinder
(model No 23-612 F573 G6-202-17 1/3 HM 115vac single phase, 3250 rpm).
It is in the process of getting new bearings (the old ones tick when
running, probably due to bits of metal in the grease).

This unit is old-time US, made of cast iron, and weighs a ton. *And runs
smoothly, except for the ticks.

The mystery is the wheel flanges. *The arbor is 0.500" diameter, and the
wheel flanges (that hold the grinding wheel) are die-cast aluminum alloy
and are about 0.425" thick along the arbor shaft, and are equipped with
two keyslots spaced 180 degrees apart. *In the arbor shaft there was a
0.095" diameter by 5/16" deep radial hole with a spiral pin pressed in,
with the tip sticking out, and engaging one of the two keyway slots
(which are 0.117" wide) of the inner flanges. *The spiral pins had
largely sheared off, and had chewed a groove and raised a divot on the
inside of the flange, where the radial pin rested. Both sides were
equally affected.

I was able to drill the pin stubs out without damaging the arbor shaft,
using a 0.088" diameter HSS drill in a hand drill, using black sulfur
oil.

My first thought was that this should have been a woodruff key, but the
keyslot is halfway between the standard sizes. *But I could mill a
woodruff key slot in the shaft and widen the keyslot in the flange
washer.

My second though was that the original design probably had a single
close-fitting but loose pin that went all the way through the arbor, and
engaged both keyslots.

My third thought was to wonder why the scroll pins both sheared off.
They don't lead that hard a life, so what happened? *Maybe I don't want
to make this too strong.

My fourth thought was to observe that few modern bench grinders have
such pins or keys. *What problem did they solve?

Comments?

Joe Gwinn- Hide quoted text -

- Show quoted text -

OK, have a look at this:
http://www.acetoolrepair.com/parts-r...or-23-249.html

This is a long-shaft buffer, it HAS roll pins. So maybe what it is is
something that's been converted or a special order item. Can't think
of another explanation. Looks like the pins drive the inner flanges,
then there's a pin that drives some sort of hub for each buffing
wheel.

Hmm. Maybe. The motor unit et al are the same. The buffer's roll pins
are 1" long and go all the way through, with 1/4" sticking out on either
side. By contrast, on the grinder, the hole is blind, and the pin
sticks out a bit less than 1/8". But maybe.

Joe Gwinn