Beaded Belt Gear for 4.5mm Chain

thingiverse

This 4.5mm-belt-driven gear, available at hardware stores, is ideal for general drive applications but initially designed for RepRap Darwin's Z-axis. To use it, first remove raft residues and ream the center hole gently. Insert an M8 hex nut into the hexagonal cavity, warming plastic if needed. Fasten on an M8 studding with a washer and nut, trapping the nut for better drive shaft keying without extra washers. Fine-tune scaling (95% in my case) to accommodate chain irregularities or imperfect extrusion.