Worm Gear Lathe Tool

thingiverse

To improve my plastruder's timing belt gear reliability, I replaced it with a worm gear drive cog. To create the gear blank holder, I printed a tool with solid infill and dipped it in acetone to bond layers. After letting it re-harden overnight, I reamed a 15/64" hole using a drill bit. Next, I prepared a brass or steel rod worm gear blank with a flat-bottomed groove near the end and a 0.4" bottom diameter, fitting it snugly around a 3mm 0.6 pitch tap. A 15/64" hole was bored through the center, and the part was cut to 0.45" length. I fitted the part into the extruded holder and secured it with a 7/32 allen wrench or bolt. Mounting the tap in the lathe chuck, I attached the holder to the tool post. With the lathe speed set to 200 RPM, I fed the part into the tap, applying cutting oil as needed, until the groove was fully rounded and threaded. Finally, I drilled a hole for a #10-32 set screw in the side of the worm gear.