Mparker, that post about lapping Tam O'Shanters (yours appears to be a hell of a lot harder than mine) got me thinking about lapping in general, and now this thread too...
I wonder if I'm too casual about it. Unless it's a hard ark or something, lapping takes me about 5 minutes, 10 minutes max if I use two grits. I draw the grid on and then I sand it off, nuff said. I check to make sure the grid comes off evenly, then when the stone grips hard to the sandpaper-on-glass I figure I'm done. Chamfer the edges if it's a new stone, adding another 2-3 minutes.
Is there anything else to it? Is there really such a range in terms of how good your lapping can be? Should I be taking extra care to apply even pressure while gripping the stone, for example? And Bruno, why is the lapping stone so superior in its performance to sandpaper-on-glass?