I have a delta dj20 8 inch jointer. When ,making multiple passes to flatten a board I am ending up with different thicknesses on each side of a 8 inch board. The tables are within .002 of the cutter head and the blades are all within .002 os each other. Do I need to go end for end on each pass. I am jointing 8 inch wide mahogany. Any help will be appreciated.