Replacing carbon brushes
1. First of all: What exactly are carbon brushes and where and when are they used?
Carbon brushes are sliding contacts which are usually made of graphite or graphite enriched metal. They provide the electrical contact to the collector or the slip rings of the rotating part in a motor or generator. Carbon brushes are used in many AC devices in and around the house and the workshop. As this is a wearing part, they are worn out after a certain number of revolutions and must be replaced. They sit in a suitable holder within the housing. The carbon brushes should have a minimum thickness of 5 mm - but if they are replaced beforehand, it can prevent unnecessary damage!
2. How are they replaced?
The device must be unscrewed. Then the carbon brushes (usually two) should stick out directly as a black block in the housing. The carbon brushes are equipped with a spring in their holder so that they can always be in compression. Since this spring is usually latched for safety reasons, it is recommended that you loosen it carefully with a narrow-slotted screwdriver. Once you have done this, the new carbon brushes can be inserted in the same position as the old ones were and the device closed back up again. When the new carbon brushes are inserted, you can usually hear the spring snapping, so that you can be sure that they are not stuck.