If the floor has layers of old finish or severe damage, 24 grit is used as a starting grit. 36 grit is the starting grit used if the floors have minimal damage or fairly worn finish. 60 grit is used to even out scratches that the 36 grit can’t. 80 grit is used to even out scratches following the 60 grit; for some wood floors, this is the final grit phase. 100 grit is used to even out scratches from the 80 grit or as a final grit for some floors.