You spray the seat check on the seat, pop in the stone, let it
pivot around in the seat using your fingernail, and any exposed
metal is where I would need to remove some metal?
The exposed metal is where the stone was able to contact, rubbing off
the disclosure powder (or whatever you use. Magic marker, machinists
layout dye, something else…) However, this does not mean every
exposed spot needs metal removed. Think in terms of a teeter-totter
on the playground. The bar swings up and down over a center pivot
point, and at each swing, contacts the ground at one end or the
other. Your stone is doing the same. You don’t want to be removing
the metal at the ends of the swing, as those are low points the stone
can touch.
What you want to find are the high points on which its pivoting.
Removing a tad of metal there will drop the stone down slightly,
lessening the amount by which it can shift. Keep working that until
it’s steady and level. Note that you won’t ever (well, never say
“never”…) get it to contact all the way around.
often, what you’ll get is decent contact at three points spread
around the stone.
On trillions you’ll usually want this good contact to be supporting
the points of the stone, since if you support at the long sides,
leaving the points unsupported, then tightening the stone can result
in what amounts to a nut cracker geometry, causing you to break off
the tips. The closer you can get to even support at more than the
minimum of three spots, the better and safer, but just keep in mind
that without some sort of cutter that actually cuts a match to the
stone shape (like a round burr can do with a round stone), it’s hard
to get full contact all the way around. Not impossible, but hard,
especially with softer stones. One hint, you may find, for some
situations, that using a manual graver to shave thin amounts of
metal off the high spots, gives you better control over tiny
adjustments than using a bur in a power tool. Takes a bit of
practice, but it’s one of those cases where sometimes the old time
honored tools are capable of better results, even if sometimes slower
(or maybe because they’re slower…)
Hope that helps
Peter Rowe