Now that the table is flat, the X Axis rails have been attached and the Y axis gantry assembled. The bearing blocks for the X and Y axises have been machined. I choose to use 1/2"-8 4-start (.500" lead) lead screws from Roton with anit-backlash nuts from DumpsterCNC. I turned the ends of the lead screws down to 3/8". The bearing blocks hold 3/8" bore ball bearings for the rotational movement, needle thrust bearings and shaft collars transfer longitudinal force to the blocks, which are anchored securely to the ends of the linear rails. The turned ends of the lead screw project about 3/4" out of the backside of the bearing blocks for attachment to the couplers.