Timing Pulley

Posted by Will on Jul 15, 2011 in Machine Work

I had heard of DIY timing pulleys made by drilling a circle of holes in a piece of material and then turning down the piece to form the teeth.  SDP/SI has some great info on pulleys including a chart of tooth profiles (http://www.sdp-si.com/D265/HTML/D265T015.html) and a center-to-center distance calculator (http://www.sdp-si.com/cd/default.htm).  The HTD series of belts looks like it has the roundest teeth so it is most appropriate for this machining method.  The calculator will tell you center-to-center distance for two timing pulleys but it also gives the pitch diameter.

This is a test part so I estimated the drill size from the drawing and drilled right on the pitch diameter.  Instead of turning away the unwanted material on the lathe I used a milling machine to remove it away with an endmill.  The pulley diameter is the same as the pitch diameter which seems to coincide with the info in the SPD/SI catalog.  The drill size, hole circle diameter and pulley diameter can all be tweeked once I have the belts to compare with the pulley