Originally Posted by
joshearl
Steve,
I draw a grid on the stone with blocks about 1 inch square. Lap until it's gone, then draw it again and give it five more laps. If the grid's all gone after a few quick laps, you know it's flat. (Repeating the grid procedure is helpful because sometimes the slurry from the stone can clean off the pencil before the stone is flat.)
As far as sandpaper, I usually use a coarser grit and then go to a high grit to polish the stone. I'll start with a 400, generally, and go to a 1200 grit for a few laps once the stone is flat.
Somebody mentioned that you should do the 8K side first. I actually prefer to do the 4K side first, for a couple of reasons. First, the 4K will wear down the sandpaper a bit, and that along with the slurry from the 4K allows the 400-grit to act like a higher grit on the 8K side. It seems to polish it nicely this way.
Also, if I do the 8K side first and then don't rinse the paper before doing the 4K side, the yellow slurry from the 8K will stain the white 4K side. That bothers me. :)
Good luck,
Josh