Beefy Small Gear with Screw Insert for Wade's Geared Nema 17 Extruder

I kept having some delamination on the screw part of http://www.thingiverse.com/thing:2521 if too much force applied.

This file uses M4 hardware. You will need an M4x16 bolt and a half-height M4 square nut. No filing on the slot or whatsoever required to fit.

You can change the sizes in the dxf file and extrude it with OpenSCAD.