How to Replace the Brush and Spring on a Dremel Rotary Tool (Model 4000)

The brush and spring assembly consists of a carbon brush with a copper spring-coil attached. The brush and spring are used to transfer power to the rotary tool's armature. The spring transmits power while firmly holding the carbon brush against the armature's commutator. The brush will wear down over time (due to constant contact with the rotating armature). If the armature is overloaded, the springs can also be burned. In either case, the brush and spring assembly will need to be replaced.

Let's get started.

REMOVING THE BRUSH AND SPRING   1. Remove the brush and spring.

a. Use a screwdriver to unthread and remove the brush caps.

b. Remove the motor brush and spring from the brush holder (it should simply slide out of the holder).

INSTALLING THE NEW BRUSH AND SPRING

  2. Install the brush and spring.

a. Align the new carbon brush with the holder and slide the assembly into the holder.

b. Secure the brush and spring with the brush cap. (Do not over-tighten the brush cap.)

c. Repeat these steps to install the second motor brush and spring.