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Has your power tool got a brushed motor … or a brushless motor? Or are you not sure? If you don’t know the answer, then you might be tempted to think that it doesn’t matter. But it does matter, certainly when it comes to tool care, tool safety and performance.
How can you find out? You’ve come to the right place.
But first, what are brushes? In a brushed motor, the 'brushes' carry the electrical charge between the stationary and moving parts of the motor. These 'brushes' aren't actually brushes, by the way – they're actually small blocks of carbon or carbon & graphite; they're only called brushes because they were originally made from copper wire and so looked like little wire brushes. |
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As you can see from this image, each brush has a wire lead (typically within a coiled spring) with a terminal attached at the free end. In certain cases, the brush itself will be contained in metal housing. |
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To carry the charge, these brushes need to be in constant contact with the rotating central part of the motor. Over time, your carbon brushes wear down, such that they’ll fail to connect, won’t connect properly or cause damage. |
Here are the signs that the carbon brushes in your power tool probably need changing:
- If you have to shake the tool or hit it to get it to start
- Burning smell: If it smells like there's something burning
- A banging sound in the motor
- Off-and-on operation as the connection gets established and then interrupted
- If you're losing RPMs and losing general performance or the tool stalls
- Excessive sparking and/or smoke in vents
Sound scary? We think so too. You don’t want to let your brushes get to this point, though: That's why it’s important to inspect your brushes regularly. The good news is that this is easy to do, because brushes are easy to locate so that you can quickly check and replace them if need be.
| Remember that the warning signs listed above can be an indication of other problems – something like a faulty switch or damaged motor parts. If problems persist after you’ve replaced the carbon brushes, take your tool to an authorised dealer. |
Here's how:
- Work on your tool on a flat, well-lit surface that’s dry and free of dirt, dust and clutter. That way, you’ll have plenty of space for any equipment and parts.
- Remove the tool from its power sources (unplug from the mains socket or remove the battery).
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Locate the carbon brush caps, normally located on either side of your power tool’s motor housing. Using a slotted screwdriver, remove the carbon brush caps and set them to one side. |
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You can then simply pull out the carbon brush. |
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It's easy to inspect it for signs of damage or wear. |
- Some tools may have a metal clip that holds the carbon brush in place; use needle-nose pliers to pull the clip out of the way so that you can remove the carbon brush.
How can you tell if your brushes are worn? For a full-size tool, when the brush is down to about a ¼ of an inch long, it's time to change it. In the case of Dremel/rotary tools, you can let it get down to about an ⅛ of an inch long. Also look out for any signs of burning, cracking, crumbling or discoloration.
To get the correct set of replacement brushes, get your power tool’s product code from the rating plate on the motor housing or from the tool’s instruction manual. In sourcing replacement parts, it’s best to get genuine parts from authorised dealers. (Don't be tempted to use no-name budget brands – they’re likely to be poor quality and could damage your tool.)
| Check your carbon brushes regularly. Make sure that you always have some on hand – they're cheap and readily available. |
Want to know more about carbon brush technology? Then read our blog on brushed vs brushless motors.
