What is the automatic stop in a carbon brush?

Carbon brushes can be found in two variants on our website. One with automatic stop and one without automatic stop. But what exactly does an automatic stop do? You can read that in this blog!

What is a carbon brush again? In short, the carbon brushes in a motor conduct electricity. A carbon brush is mounted on the fixed part of a motor and is pressed against the rotating part (commutator) (read more about the function of carbon brushes: what are carbon brushes?). This causes the carbon brush to wear out over time. When the carbon brushes are worn, they will no longer make contact with the commutator and the machine will stop running. But it can also happen that this causes the machine to spark a lot and damage the machine. You will then have to replace the carbon brushes as soon as possible to prevent further damage.

A carbon brush with an automatic stop in it is made to protect the motor against this unnecessary damage. With a carbon brush with an automatic stop, a small spring will expand so that the motor stops running. The cross-section of a carbon brush with automatic stop is shown below:

As you can see, there is a small spring next to the cable. This spring will push itself out as soon as the carbon brushes are almost completely worn out. In this way, the carbon brush no longer makes contact with the commutator and the machine immediately stops rotating.

The following example clearly shows what actually happens with the carbon brush. The upper carbon brush is a new and unused carbon brush suitable for Bosch machines. Below that we see two of the same carbon brushes, but worn out.