In thread "Rockwell 6" bench grinder - anti-rotation pins" first posted
on 4 March 2012, the matter of the anti-rotation pins and their reason
to exist was debated. The upshot was that I decided to retain the
anti-rotation feature.

I have now finished rebuilding the grinder:

Both bearings were replaced. The bearings are commodity type 6203, with
double seals. Cost $10 apiece. Installation required making of a pair
of aluminum-tipped pushers, so the new bearing could be tapped into
place with a lead hammer. The ticking is gone.

The mating faces between motor end bells and wheelguards were flycut
flat, to make a wobble-free joint. The original surfaces were as cast.
Removed about 0.010" of stock from each part, each of which is about
1/4" thick. Don't know how necessary this was, but with the motor apart
the machining was easy.

Milled two 0.125" wide feather-key grooves in the motor shaft, under the
inner flange washers. Again, with the motor apart and the original
bearings removed, this was easily done on the vertical mill.

Faced the diemetal flange washers, so the wheel-bearing faces are
parallel to the faces that rest on the shaft shoulder or nut face. They
were off by a few degrees, enough to cause a large wobble.

The diemetal (Zamak?) machines like cast iron, the chips being a coarse
powder, and it turns out that the best way to get good surface finish
was a steady flow of compressed air, to blow the chip dust away before
it gets back into the cut. The difference in finish was dramatic.
Cutting wet didn't work near as well, but I suppose flood cooling would
have washed the chips away too.

Using a square jewler's file, filed one keyway groove in each of the
inner washers a bit wider, to accept the 0.125" key.

Replaced the very worn abrasive wheels. Coarse is 46 grit, and fine is
100 grit. (I find 60 grit to be too close to 46.)

Machined a pair of aluminum arbor adapters to adapt the 1" holes in the
wheels to the 0.500" arbor shafts. The adapters are a hand push fit in
the wheels, and a slip fit on the arbors. This largely prevents radial
motion of the wheels, which was quite large before.

After dressing the wheels, the vibration is minimal, and one can make
very precise grinds.

You may recall the saga of the vibrating 8" Ryobi bench grinder,
documented in multiple threads over 2009. This rebuilt old 6" Rockwell
grinder makes the Ryobi look sick, even after the various improvements
made back then. The Ryobi is a clumsy clone of the Rockwell, which is
based on Baldor grinders. Ryobi left no corner uncut. (The motor unit
of the Rockwell is made by Baldor.)

I have also found another reason for the anti-rotation feature - it
makes wheel removal and installation easy. One just holds the wheel in
one hand and a wrench in the other, and tightens or loosens the nut,
without fuss.


Joe Gwinn