Introduction: How to Clean the Commutator of an Armature

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Video tutorial on how to clean the commutator of an armature for a motor. Having a dirty commutator can cause a poor connection between the brushes resulting in the motor not functioning correctly. If you are also replacing the brushes of a motor, it is also important to clean the commutator before usage again.

Tools/Supplies Needed:

  • tooth brush or nylon brush
  • electrical contact cleaner
  • safety glasses
  • rubber gloves
  • drill with larger chuck
  • 600 grit aluminum oxide sandpaper
  • plastic scriber
  • file
  • razor knife
  • cutting blade

Step 1: Prep

Clean the commutator using a toothbrush and contact cleaner. Spray the contact cleaner on the commutator, then agitate the surface with the toothbrush. This will remove any oils, dust, dirt, or any other contaminant which can cause connection issues and prevent any contaminants from traveling when we clean up the copper surface in the next step. Give the rest of the armature a wash down with contact cleaner to remove any unwanted dirt or debris. Only use an electronic contact cleaner, otherwise you can risk damaging the insulation within the armature.

Step 2: Resurfacing

Next we will be resurfacing the commutator, removing any pitting, marks left from arcing, imbedded dirt, etc. Using only aluminum oxide sandpaper, 600 grit, rip off a piece roughly about the wide of the commutator. Holding the armature in one hand, wrap the sandpaper around the commutator, light pressure, turn the commutator in a full rotational motion and not just back and forth. Sand in the path of travel and not against it, we do not want to create and uneven surface as this will cause issues. Now as a better more reliable method, we’ll use a drill. Not all armature shafts are the same size, therefore you may have an issue using a drill as some chucks do not open large enough. Have a piece of sandpaper which is the right width and also long enough to pick a couple inches away from the commutator. This will allow for fairly uniform sanding, similar to using a lathe. Ensure any surface imperfections are removed. Any deep damage can be too much for sandpaper, therefore you’ll need someone to recut the surface on a lathe.

Step 3: Final Clean-up

After that, give the commutator a final clean up with contact cleaner. Clean in between each of the bars using a plastic scriber to remove any build up of debris from before or after the resurfacing. Next is checking the mica depth between each of the bars. For this armature, it isn’t needed, but in some scenarios the mica between the bars maybe too high, preventing the brushes from properly riding on the commutator. The mica should be around 1mm lower than the bars, this is also known as mica undercut. To cut the mica back, there are specific tools for this procedure such as a cutting blade, file, but a razor knife can also be used.

Step 4: All Done!

Finally we will be left with something such as this and the motor is now ready for reassembly.