worn bushes?

i repair powertools for a living, and run one of the uk's top powertool service companys. drills are amongst the most common item to wear out brushes!
what your saying is sometimes true. although it is increasingly likely for tool companys to use cut out brushes which do away with the rough running and just turn the tool off to save the armature from wear.

force 10 powertools
February 2011

some brushes do ''switch off'' suddenly as they have a spring inside them designed to cut power to the commutator when the carbon conductor runs out. to check that the circuit to the brush holders is working it is common practice to attach multimeter leads to the brass brush holders and set it to volts, then pull the trigger of flick the switch and read your multimeter. if the meter reads the correct voltage then the problem is most likely brushes. it is important to notice at this point the small chance of giving yourself an electric shock. AVOID TOUCHING LIVE PARTS. or contact me rugjnkn@aol.com

Matt, Jenkin Repair Services
January 2009

Motor brushes do fail but I have never had to replace them in any electric drill I've owned.

A fault like you have is more probably, trigger switch, driving circuit, broken connection or battery related before being the motor brushes.

When brushes do fail you usually get a period of rough running as they begin to disintegrate - they seldom fail suddenly.

Peccavi
January 2009