Replace Slim Angle Grinder Carbon Brush

If your power tool (angle grinder, drill, sander, etc.) starts intermittently getting hot, not having full speed or full solid rotation during use: you may need to take a look at the carbon brush condition.

If the carbon brushes are too short, they don't have sufficient length to reach the motor commutator and will not be able to perfectly make contact with the commutator.

Above photo depicts worn out carbon brushes on top, and new carbon brushes on the bottom. For carbon brushes with copper braids on the side like these, the copper braids will restrict the carbon brushes to go all the way toward the commutator, because the copper braids will get caught by the brushes metal compartment. This is the reason, above "worn out" lengths still showing some carbon thicknesses that are actually wasted (about 3 - 4mm wasted thickness).


Repair Steps

1. Hunt for your tool's parts breakdown schematic.
     This parts breakdown provides useful information about the structure of the power tool, and part numbers (if you need to replace some part(s))

    Example for Makita 4" Angle Grinder (GA4030):
    https://www.partswarehouse.com/Makita-GA4030-4-Angle-Grinder-s/323873.htm

MK-GA4030 4. Ball Bearing 607Llb MK-210034-7 5. Insulation Washer MK-681636-0 6. Armature Assembly, Inc. 4,5,7 115V MK-517646-0    .    ..    ... 40. Brush Holder 6X9 MK-643839-4 41. Carbon Brush Cb-458 MK-194721-5    .    ..    ... 2. Unscrew the back-cover  3. Release the carbon brush' pressing spring.    You can use any thin mild strong tool (for example small screwdriver, bamboo stick, tweezers,...

4. Pull the carbon brushes out and release the crimp connections
    I used long nose pliers to pull out the crimp.

5. Source for replacement carbon brushes. 
   The exact part for MAKITA GA4030 is CB-458 (6mm x 9mm). However I could not find this exact part. I decided to purchase CB-459 which is pretty similar in size, just a little difference at the crimp. I expanded the crimps a little bit for them to be able to plug to the male connectors.

6. Close back everything with the same tools and reversed step sequence.



Non Commercial Share-right:
Some images and contents of this page are retrieved from ifixit.com because I missed taking some photos during my grinder repairs. They are non commercially shareable with proper credit under the Creative Commons Attribution Noncommercial Share Alike license.