I have seen the methods for setting a mortise bit and chisel but do not know what part of the bit to rest on the workpiece when getting ready to move the chisel up to it's correct position. Depending on whether you set the bit on the tip of the point or the flat cutting part would make as much as 3/16 of an inch difference.
Do you measure from the tip, the vertical cutting edge or the horizontal cutting part of the bit?