I need some help if possable. I have a central machinery dove tail jig. I have tried to cut the dovetails per the instuctions but they just don't come out right. I'm useing a 1/2" bit 1/4" shank, the comb is 1/2" wide fingers. Do I need to use a 1/2" shank bit to cut this, Or a 1/4" wide comb? The horazontal piece comes out round at the end of the cut is this right ? or am I doing something wrong.