How to Convert Cordless Drill Motors for use in Robot Drives
by Peter Smith

Many robots use small DC motors and a gearbox to reduce the RPM and to increase torque. One popular way of doing this is to use the combined gearbox and motor from a cordless drill. These typically have a 12V-18V motor attached to a 36:1 planetary gearbox.

There are two main sources for suitable drills. Harbor Freight (www.harborfreight.com) and Homier (www.homir.com). Harbor Freights Model 91396 and Homier 02899 are suitable. Avoid drills that have “hammer” features and remember, the cheaper the better. It should not be necessary to pay more than about $25 per drill. Various voltages are available but the drills tend to use standard 550-sized motors, so even if the voltage of the one you get is not really suitable, the motor can be replaced by another more suited to your application.