TOM X-Axis Follower - Recessed Bearing Bolts

NOTE: I ended up switching to this follower instead: http://www.thingiverse.com/thing:8625 It works quite nicely.

Added a recess on the back side to insert the bearing bolt heads into. That way you can put nuts on the bearing side to keep them secure instead of relying on drilling/tapping the plastic. I also made the default for the dimensions of 693 bearings. The comments in the scad script show you what to change for whatever bearings you have. Note: 624 bearings are too large! So anyt