Repair a power tool with a simple brush change
Over time I knew something was going wrong with my old chopsaw. First the automatic blade brake stopped working, then the motor wouldn’t turn on sometimes, and then it quit altogether. I suspected that it was the motor’s brushes, and I was right. By the way, brushes are little spring-loaded, carbon-tipped gizmos that transfer power to a shaft called a commutator, causing it to spin. That’s how an electric motor works, basically.
I’m no motor expert, so I procrastinated for a while. But when I finally dove in, changing the brushes turned out to be easy.
First I unplugged the tool and and unscrewed the caps that hold in the brushes. I also removed the cover on the end of the motor, to get a better view. As soon as I pulled out the brushes, the problem was obvious. One had come apart completely.
The next step was a Google search. The terms “motor brushes” brought up tons of options. The certified replacements from DeWalt were over $20, but I heeded some online advice and bought generic brushes that were the same dimensions as mine. Six bucks.
I also read online and in a past FWW article that the carbon block on a brush needs to slide easily forward and back in its slot, so its spring will keep it pushed against the commutator. The fit on my new ones was too tight, but as I had read, the little carbon block can be trimmed with a file, sandpaper or even a bandsaw without hurting its performance.
A little rubbing on a sanding block, and both brushes slid right up against the shaft where they belong. Then I put the caps and cover back on, plugged the saw in, and made my first cut in over a year. Blade brake worked perfectly too. I had forgotten the saw even had one!
If your chopsaw or router stops working well, or stops working altogether, don't be afraid to investigate. Unplug the tool and dive in. I started by taking off the small cover at the end of the motor.
Then I unscrewed the little caps that hold in the motor's carbon brushes.
The problem was obvious right away. The brush was in pieces. No electrical connection at all.
This is what the brush is supposed to look like. I bought a pair of these online for 6 bucks.
One cool thing about carbon brushes is that they can be sanded or filed to fit. Mine were very close in size to the old ones, but too tight in their slots. A little sanding took care of that in seconds.
Then they just slide into place. I made sure they were pressed up against the copper shaft inside the motor.
Then I screwed the brush caps and blade cover back on, plugged in the saw, and crossed my fingers.
It worked just like it used to! Nice to fix something rather than replace it. Saves a lot of money, and makes you feel smart!