Repair Noisy Bearing Angle Grinder

Memperbaiki Gerinda Tangan yang Bersuara Berisik karena Bearing Rusak

Noisy angle grinder, and quickly getting hot: are most probably caused by spoilt bearing. The balls inside the bearing run randomly without guide.
There are 3 bearings inside an angle grinder. Two are located inside the gearbox. The other one is after carbon brush area. Following instructions are more useful for the 3rd bearing.

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. Open the grinder lock nut using the lock wrench 3. Remove the safety cover Unfasten the screw locate the locking protrusion and pull the safety cover out 4. Unscrew the back-cover  5. Release the carbon brush' pressing spring.    You can use any thin mild strong tool (for example small screwdriver, bamboo stick, tweezers,... 6. Pull the carbon brushes out and release the crimp connections     I used long nose pliers to pull out the crimp. 7. Unfasten 4x PH2 screws which join body and gearbox together 8. Pull the gearbox away from the body. You may need to use slot screwdriver bit to spudge the gearbox away. NOTE: not to puncture too deep until breaking the fan blades inside. 9. Pull the broken bearing away from the armature assembly. The best is using bearing tracker. Or you can use 7mm spanner, hold it below the bearing bore, while knocking a Ø5-6mm bolt downward to the armature shaft. knock it gently. Broken bearing: Search for same bearing type as per the schematic: 4. Ball Bearing 607Llb MK-210034-7. The important thing here is searching the same size and type bearing. The original bearing is "sealed" type, which will be very crucial in preventing dust penetration into the bearing, and in turn destroying the bearing. Here is example of "double sealed 607 bearing" (607RS) 9. Knock in new bearing to the armature assembly. Use hammer to knock the bearing gently and evenly. You can also use back the 7mm hex spanner hole to push on the bearing bore evenly. Knock as close as possible to the armature shaft for accurate bearing down sliding. 10. Install every part back and ensure repair is effective. 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.