How To Check if Carbon Brushes Are Worn & Need Replacing?

Time to change your Carbon Brushes?

Short summary:

The most obvious symptoms of bad motor brushes are poor performance, loss of power, sparking, and a burning smell.

The best way to know for sure that the brushes need changing is to remove the old brushes and check if they've worn past the "auto cut-off" line, which indicates they need replacing.

Enjoy the full article below, or visit Top Deals Online to buy new carbon brushes for your tool.


There are many different working parts within your power tools such as switches or carbon brush caps and that can often make it difficult to identify which part of your power tool is causing the problem.

With so many working parts, it is inevitable that things will go wrong, and whether that is through a fault or heavy use, it is important that you can identify where the problem lies.

One area of your power tool that can cause problems is the carbon brushes and when the time comes to replace them, you need to know that they are causing your power tool problems.

How to Know if Your Carbon Brushes Need Replacing?

When your motor brushes are worn, you will notice the following signs:

  1. Reduced performance: One of the first things you'll notice is the tool will stop performing as well. You may have to shake it to get it going, and it will likely not achieve the high RPMs it used to.
  2. No Power/Inconsistent: If your carbon brushes are wearing out is if the tool starts cutting out during use. This is a clear sign they have completely worn away. 
  3. Check your brushes: If you can easily get access to where the brushes are installed most are located near the motor housing accessed usually via a Carbon brush screw cap you can unscrew the cap or open the motor housing and take the old brushes out you will see that if the there is little or no carbon left then the brushes will need replacing. Most of our brushes have a AUTO-CUT off feature where a small pin from the carbon will pop out and stop the motor safely this will be a sure indication that new brushes are needed.
  4. Sparking / Arching: While minimal sparking is common in power tools, frequent large sparks are not, this could be down to poor brush to commutator contact surface all brushes need to match the arc of the commutator to ensure correct surface contact. It also can be a sign of excessive brush wear, a damaged or dirty commutator, or an incorrectly installed or incompatible brush. You can monitor the sparks through the cooling vents on your tool, which should help you gauge if it's getting worse.
  5. Burning smell: Is caused by arching and other factors, there are different smells associated with burning from a power tool and if you do encounter this you should immediately stop using the power tool and seek a professional tool repairer to diagnose the fault. It may not be a case of changing brushes so the distinctive smell needs to be identified before diagnosing a solution.
carbon brushes

What are Carbon brushes & Why are They Important?

Carbon brushes are a small but essential feature of all power tools (1). They conduct the electrical current between both the stationary and rotating wires inside motors. They handle a lot of energy, and so are designed to wear over time.

Once a carbon brush starts to wear down, you may notice performance issues with your power tool.

However, identifying when that time comes can prove difficult, but spotting the signs early can help you to get them replaced quickly while preventing further damage to your motor and your power tool, which takes us to the next step.

How long do carbon brushes last? Click here

worn out carbon brushes

Can you fix carbon brushes?

You can't fix a worn or damaged carbon brush, so all you can do is replace it with a new one, which is actually quite simple to do.

Need a new set of carbon brushes? Top Deals Online is a dedicated supplier, where you can search by Tool Model here, to help find the exact brush for your tool.

We stock brushes for popular models like the Titan TTB280DRH and the TITAN TTB278SDS.

How to change your carbon brushes on a Titan SDS Drill

Benefits of Maintaining Carbon Brushes

Your power tool might be something you use at home or it might be something that you use for your job on a daily basis, whatever it might be, you should consider actively maintaining your power tools. While it is acceptable to let your power tools show you that it is time to replace the carbon brushes, it is not always the right thing to do.

There is no need to check the tool on a daily basis but every now and again, it can help to take a look at the carbon brushes to make sure that they are looking good and fit for purpose.

You should not leave worn carbon brushes inside your power tool for too long as this can damage the armature which is a costly repair itself. Therefore, keep an eye out for the clear signs of underperforming power tools, bad smells and sparking as this will indicate that the carbon brushes need replacing.

Read more about maintaining power tools here.

Change you carbon brushes or risk damaging your Armature

How to Test If Carbon Brushes Need Replacing?

To test your carbon brushes, monitor themuntil they are worn down to around a quarter of an inch, as this is usually a good time to replace them.

If the brush displays signs of breakage, crumbling or burning then it should be replaced.

If there is any change in colour to the spring (such as rainbow patterns), this could indicate that there is a broken lead in the spring, and so should be replaced.

Also, if the spring has collapsed, then that will mean that the carbon brushes will also need replacing.

Guide: How to Change Carbon Brushes in Power Tools

What do Worn Carbon Brushes Look Like?

When a carbon brush reaches less than 50% of the total size of the carbon brush holder, it's worth considering replacing it. This is a rough guide as to how large the original brush was.

Here are some images below to illustrate what a worn carbon brush looks like:

worn carbon brush

damaged carbon brushes

worn makita carbon brushes

How Carbon Brushes are Used In Different Power Tools

Carbon brushes are used in a variety of different power tools, including drills, saws, grinders, and more. The role of the brush in each tool may differ slightly, depending on how the tool is designed, and so the symptoms of a wearing brush will likely differ per tool.

For example, a worn out brush in an angle grinder is likely to show as sparking (due to the high speed of the motor), whereas a lower-speed tool wouldn't show such a noticeable sparking. Precision tools like jigsaws or routers are likely to show signs of inconsistent speed and lack of control as the brushes wear out.

How To Make Your Carbon Brushes Last

Prevention is always better than a cure, so here's how you can work to keep your carbon brushes as long as possible:

  • Regular cleaning - remove any dirt or debris from your tool regularly.
  • Using the tool within its capacity.
  • Proper storage - store your power tools in a clean and dry place.
  • Lubrication - if appropriate, use lubrication on the moving parts of your tool to reduce friction/wear.
  • Consistent power supply - fluctuations in power can damage the motor of your tool, so ensure you use a power source with a consistent supply and surge protection.

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