How to change Carbon Brushes in power tools

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Changing carbon brushes - The black circular cover with the slot holds in a carbon brush.

These are small easily replaceable parts, that have to be in good condition for your tool to work.

""In electrical engineering, brushes conduct current between stationary wires and moving parts, most commonly in a rotating shaft. Most importantly, in an electric motor, an alternator or electric generator, the coils of the rotor have to be connected. To accomplish this, two metal (copper or brass) 'slip rings' are affixed on the shaft and springs press braided copper wire 'brushes' onto the rings which conduct the current. Later, these copper wire brushes were replaced with carbon blocks — but these blocks are still called brushes. As the brushes are slowly abraded, they may have to be replaced, if this is possible. If the copper rings are split into parts with "interlaced" connections, the arrangement is called a commutator"  This quote from Wikipedia, explains the workings  far better than I can.

Above is a shot of the back end of my Makita sabre saw, showing on the top the black plastic button that retains a carbon brush.  There is another one opposite, underneath the saw.

Clean around the holes first before you open them up, I didn't as you can see here.  Looking at the photo below reminds me that if any of the crap around the hole drops inside, it could make things worse. ( A case of do as I say, not what I do  :-).

If the tool stops working or if it starts spluttering with  sparks seen through the vent holes it could be a sign that the brushes are worn .  They are cheap, and easy to replace yourself.  Sometimes a quick fix is to just clean them, blow out the dust and replace them and the machine works OK again.  Get new  as soon as you can and replace the old ones.

Changing carbon brushes - This brush is in good condition, they wear down to a quarter of this size before giving trouble.

When replacing old brushes after a clean put the brushes back in the same way they came out. They bed into a shape, so keep the same orientation.

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