In our first video of the series, we have tested a hammer drill that we found (in pieces) in a crate. While it seemed to be working, there are a few things that need to be solved before claiming full success (and daring running the hammer drill at full speed):
1) tackle the broken brush problem
2) remove the rust on the stator and armature
3) clean the commutator
4) Find 4 new bolts & clean the drill
Today, we will work at solving issue #03: clean the commutator.
► VISUAL INSPECTION & CLEANING
At first sight, the commutator shows a series of darker bronze colored streaks, and at the bottom, a clear line of shiny copper indicative of improper commutation.
Now remembering that, when we found the engine one of the brushes was broken off, this seems to align with a mark the broken brush could have left. We however still need to further clean the commutator to assess for any damages to the copper.
Note: I have seen people using contact cleaning solutions to clean a commutator, but I'm not a fan of it since cleaning solutions could damage the ""plastic"" wire insulation of the windings and that would be the death of the engine. So, at this stage this is for me just old-fashioned cloth and the sweet nylon fibers of a scrubbing sponge.
► VISUAL INSPECTION & POLISHING
Having cleaned the superficial dirt, I can now clearly see and feel some grooves on the commutator. I'm not sure what have caused this, but this is not good since dirt can get in the grooves and limit the current flow through the brushes. Maybe this actually caused arcing and the brush to break off in the first place...
At this stage, I have to improvise. I cannot polish the commutator with a commutator cleaning stick while the motor is running since the plastic housing is in the way. I also do not want to take the armature out of its gearbox to place it in a drill or a lathe and help with the polishing process, so I have to go the route of manual polish.
This is also a bummer since I only have silicon carbide sandpaper (400 grit) at this stage, and I have read somewhere that you should only use aluminum oxide for the job. I'm not sure why that is though, maybe that the dust created is more conductive and prone to short the anchor. I will compensate in any cases by cleaning the whole thing extra thoroughly.
The last step is to clean the mica between the slots of any debris and dust, confirming also they are still at their recommended height (around 1 mm lower than the bars).
► FINAL INSPECTION & CONCLUSION
There are still at this stage a few grooves left, but I'm happy to stop here to limit the chances of altering the commutator symmetry. The grooves left are after all only making contact with the outside edge of the brushes, so we should be fine. Finally, our cleaned armature looks ready for reassembly and final test of our hammer drill.
We can always after the hammer drill has run for some time come back and do a quick check to assess if further polishing is needed.
► TIPS
* Take your time and check progress
* When done, do not put your fingers on the copper or you will leave dirty marks (like I noticed the day after...)
► The previous episodes:
► EPISODE 1: Checking For Completeness And Damage
[ Ссылка ]
► EPISODE 2: Repairing The Broken Motor Brush
[ Ссылка ]
► EPISODE 3: Removing Rust From The Armature / Stator
[ Ссылка ]
► EPISODE 5: Final Cleaning and Reassembly
[ Ссылка ]
► EPISODE 6: Repairing / Rebuilding The SDS Chuck
[ Ссылка ]
► DISCLAIMER
Always make sure you operate in a safe and secure manner.
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