I wsa piddling with my machine [basically a Joes 2006] yesterday, squaring up the bed .I ran a pointed cutter just deep enough to make a shallow furrow in the bed in the "y'axis.Then I brought the cutter back to the side and did the same in the "x" axis.the two furrows were not even close to being square [at 90 degrees to each other].I am using a single central screw to drive the gantry,do i need two outoard screws to prevent racking orare there some tricks to alleviate this problem. regards mike hide.