I can only get precise 90 deg edges when using an upcut endmill? When I use a downcut endmill I always get a taper, outward, from top to bottom. Doesn't matter if I use a conventional or climb cut, doesn't matter if I add a separate last pass of 0.002 to 0.005", in the same or reverse direction. But if I use an upcut endmill I get exact 90 degree edges.
It happens on both ends of a board, so it can't be related to tramming. I don't think it's runout on the Makita router, either, because upcut endmills give me 90 degrees. The only thing I can conclude is that it's related to bit flex, but I don't understand why. Both bits are new, and both are 1/4". Dust extraction seems about the same for both bits, too. I don't get it. Anyone have any insights?
John