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What are Carbon Brushes and How Do They Work?

what are carbon brushes and how do they work in power tools

What do carbon brushes do?

A carbon brush, also known as a motor brush, is a very small part of an electric motor that conducts the electrical current between stationary and rotating wires inside the motor/generator.

Carbon brushes are typically made from one or multiple carbon blocks (including copper graphite, natural graphite, electro graphite, silver graphite, bonded carbon, and pitch bonded carbon), with one or more terminals. Carbon is used as it's a reasonably good conductor of electricity, while it is soft enough to give a consistent contact point. However this soft property means it does wear over time, and hence the need to regularly replace carbon brushes.

You will typically find more than one carbon brush in each motor, and there are different types for different types of motors/tools.

Why are carbon brushes used in electric motors?

Carbon brushes work by reducing the damage to the motor, by carrying the current back and forth between the stationary and moving parts of the motor. Instead of having an integral part of the machine wear away from this process, these are easily replaceable parts that are designed to wear away.

If your power tool isn't working, then check out our range of replacement carbon brushes for power tools here.

Learn more about how to know when to replace a carbon brush here.

How much do carbon brushes cost?

A pair of carbon brushes costs between £3.50 and £6.50. This is a lot cheaper than replacing your power tools, making it a very popular options.

Pros and Cons of Carbon Brushes

Pro 1: They transmit current to moving parts:

A carbon brush is a sliding piece that transmits electrical current from the static part of a motor to the rotating part, minimising the sparking between the two contacts.

Pro 2: They are necessary for torque:

"For getting torque in the same direction throughout the rotation, it is necessary to reverse the direction of current flowing through the rotor winding in every half cycle.

This is called “commutation” and it is achieved by supplying the rotor current through brushes.

The brushes are fixed to stator and they connect to copper plates fixed to rotor. As the rotator rotates, the brushes supply current in the right direction." source

Cons: Maintenance

They do have their downsides though, as they need maintenace because they're a wearable part. You may also have to periodically clean the commutator and the stator in the tool.

Replace your carbon brushes:

If you want to replace your existing carbon brushes, then checkout our online store.

We stock replacements for top brands like Bosch, Dewalt, Makita, and Evolution.

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