Special attention should be paid to the installation and operation of the carbon brush holder, because the correct installation and correct use of the carbon brush determines the service life of the carbon brush. The distance between the bottom edge of the brush holder and the surface of the commutator or collector ring shall be kept within 2~4 mm. The distance is too small, brush frame easy to rub damage commutator or collector ring is too large. The brush is liable to jiggle and cause damage. Make sure the brush works on the surface of the commutator or collector ring and not near the edge of the collector ring. If the carbon brush is improperly installed in the cold state, the carbon brush may not fully contact the surface of the collector ring after the motor's large shaft expands in the hot state. Grinding the arc surface of the carbon brush to make it basically consistent with the commutator or collector ring.

Due to the gap between brush and carbon brush holder, and because the carbon brush rack fixed parts (such as the brush rod, etc.) in tiny deformation under the action of stress, can make the sectional curvature radius was slightly greater than the commutator brush or collector ring radius of curvature, thus in the process of the motor running, is not in contact with the commutator or collector ring all brush section area, but only part of the area. Therefore, it is necessary to grind the carbon brush on the arc surface to make it basically consistent with the commutator or collector ring. In practical operation, the contact area of the arc surface of the brush to the commutator or collector ring shall not be less than 75 percent of the cross section of a single brush.