[ATM] grit size on tile tool

[horace r davis]

On my 16 in mirror I was using #120 grit for 2 1/2 hr but I am not making
contact with all the tiles I have a lot of # 80 grit left so thinking of
switching back to wear in the tool and fix the unevenness in the mirror.
I have extra tiles so I could always add another layer if they wear too
thin. It looks like I had a small ridge in about 3 inch from the edge
which caused  these tiles too be high and not making contact the
polyurethane in this area. The polyurethane has not come off some of the
tiles in this area. In other areas the glazing is off on the edge tiles
as well as the center tiles.
the tool is not wear in the center or the outer edge.