This is a modification of one of the parts from iamjonlawrence's brilliant Y-axis conversion (http://www.thingiverse.com/thing:180146) to toothed belt for the PrintrBot Simple. He had a problem that, when he really tightened the belt, the bearing pillars weren't up to the strain. He's designing a part for the tops of the bearings to help, but I thought there was a bit too much hollow space in the pillars. So, I just filled them in a bit. This design is untested, and will take longer screws than the original, but I have confidence that it will hold up. I have hardware coming this week, and will report back. EDIT: I did a dry assembly with just some 20mm M3 screws, and I did notice that the screws will have to be JUST the right length. If they extend past the nuts, they will be digging into wood and putting torque on the part. EDIT: I went ahead and designed a top brace that also acts as a shim for extra length of your screws (edit thickness in OpenSCAD). EDIT: Added a version with enough clearance for a nylock nut. This is the version I have on my PrintrBot Simple, and it's working like a champ. EDIT: If you own a Simple, you should REALLY check out iamjonlawrence's profile! He's developed a BUNCH of great mods to improve the Simple.I printed in PLA, 0.2mm layers, 30% infill, with support (for the nut captures in the base; I haven't got the hang of bridges yet), fan on as always for PLA. Since the nut is at the very base, if the screw extends past the nut, you will have to either grind the end of the screw to fit, or drill relief holes in the PrintrBot Y arm (use the part as a template). EDIT: You can use the top brace as a shim and brace. You can edit in OpenSCAD for 1mm or more. I have included STL files for 1.0, 1.5, and 2.0mm.