Beaded Belt Gear for 4.5mm Chain

thingiverse

This is a gear that can be driven using the 4.5mm beaded belt, or ball chain obtainable from many hardware stores. This is useful for general drive applications, but was originally designed for the Z axis on RepRap Darwins. Instructions Peel off bits of raft and lightly ream the centre hole to remove any trailing filament. Push an M8 hex nut into the hexagonal cavity - it should be a snug fit. If it is too snug warm the plastic with a hairdryer to reduce the chance of splitting the gear. Fix on M8 studding by applying a washer and another nut to the flat side of the gear and tightening against the gear. The trapped nut provides a good key onto the drive shaft and reduces the need for washers. The "95" refers to the scaling factor applied over my calculated dimensions. Scaling up and down by a few % may be needed if your chain is slightly out or your printer extrusion isn't quite perfect.