by John Henry
In normal use, electric drills require little maintenance beyond periodic lubrication and, after considerable use, replacement of the motor brushes that make electrical contact with the rotating commutator. Since maintenance varies with make and model, your best guide is the instruction manual that comes with most new drills. If no instruction manual is available for you to follow, make a rough pencil sketch of the visible parts at each stage of disassemble to guide you in reassembly.
Some drill bodies are of the "clamshell" type—two halves held together with screws. You lift off the top half, leaving all internal parts in place in the bottom half. Old grease should be removed from the gear case and replaced with grease made for drill and saber saw gears. This grease is available in tubes at hard-ware stores. Motor and gear shaft bearings (the bushing type) should be lubricated with light machine oil sold for general household use unless some other lubrication is specified by the manufacturer.
Ball bearings are often permanently lubricated and sealed during manufacture and therefore require no subsequent oiling. Your drill will let you know when it is in need of fresh grease and lubrication: It will start sounding unusually noisy. It is always better, however, to lubricate an electric drill well before it gets to this noisy condition. With some drills, you will have to remove the front end to expose the gear case and the cover section of the handle to expose the brushes. Some drills have brush caps on opposite sides of the body at the rear.
To replace the brushes, merely remove the caps, lift out the spring-loaded brushes, and insert the new brushes and the springs. Take care not to lose the springs. In the absence of instructions or a parts list, take the brushes to your dealer to be sure replacements are correct. Always replace both brushes, never one at a time. Thanks for reading this page on drill maintenance