I'm doing cutouts, I have the bit run around 3 or more times so I don't try to cut out 13/16" thick lumber all at once. The problem is each cut is a little larger from the last. Meaning if the cut out is 6"x6" the first pass will be correct but the 2nd pass will be 6-1/16 x 6-1/16 and 3rd pass will be 6-1/8 x6-1/8 I have tried several pcs and its off each time. Please help.