Mark,

I read with interest your most recent post. Veritas also sent me new
platters and the milder abrasives. Unfortunately, I didn't have as much
success as you and I'm still having problems. This became most noticeable
when trying to sharpen a 1 ½” Hock plane blade that was 3/16” thick. This
blade as you can imagine has no flex whatsoever and it is nearly impossible
to finesse it in order to straighten out the micro bevel. In this case the
micro bevel was nearly ¼” wide on one edge before a bevel started to appear
on the opposite edge. It was so bad in fact that I wound up having to
re-hone the edge on a water stone.

As I pointed out in my original post, I've measured a wobble of .005” at the
outside edge of the platter (actually ½” in from the outside edge). I spoke
to George Hammond at Veritas Tools and he told me this was within what they
consider a normal tolerance. I originally didn't think this would make much
difference, but after some additional thought it occurs to me that this
could make a significant difference and may well explain why the outside
edge of the blade is ground faster than the inside, resulting in the blade
not being square.

Let me try and explain. Assume for the sake of this example that the
downward pressure on the tool holder is constant and that the blade holder
is held stationary. On every revolution the outside edge (perimeter) of
the platter rises slightly and therefore applies more grinding force to the
outside edge of the blade. As the platter rotates through another 180
degrees the grinding force on the outside edge of blade is very slightly
reduced in relation to the inside edge, but because the relative velocity
at the inside edge is less (and the amount of wobble is also less as you
approach the center of the platter), the net result is that that outside
edge of the blade will still be ground faster. This would also explain why
it's easier to obtain a square edge on a ¾” chisel than a 2” wide plane
blade.

The reason that some users may have better luck than others may simply be
because their machines exhibit less platter wobble. Before I totally give
up on this thing, I'm going to shim the platter at the hub with some .001
brass shim stock and see if I can reduce the wobble. If I can and the
situation improves I'll be a very satisfied (and wiser) user. If not, it's
back to the water stones. As it stands right now, I can't recommend this
system to anyone.

Joel