The motor brushes in your Dremel tool will wear down with normal use so they should be checked every 50 hours or so. To check them unplug the tool and unscrew (lefty loosey) the brush caps with a small flat head screwdriver. The carbon brushes are held in with springs which should come out easily or with careful prying with the screwdriver if needed. If either of the carbon brushes is less than 3.5mm long they should both be replaced.
For Dremel Models 4200 and 4300
Size: 7.6 x 6.4 x 4.9mm
Includes: 2 x Carbon motor brushes with contact springs
