People, I'm not sure if this is the best group for my query but I'lll give it a try. I have an electric lawn mower that was made by Sears way back in1975. The nameplate rating is 120VAC - 10A. No other information is available. The mower has an electric brake feature when shut off and the mower has worked fine for many years (obviously). Yesterday while mowing, the motor started to slow down and then died. I suspected worn out brushes. I took the motor apart and indeed one of the brush wires had disconnected causing the brush spring to carry the current until it lost it compression due to extreme heat.
I didn't bother even checking Sear for replacement brushes as they stopped supporting this tool many years ago. So I figured, how hard can it be to find some replacement brushes. I went to my local ACE hardware and found a set of brushes that were the correct size including the brush wire guage.
I noticed that the motor commutator was very black probably from brush dust and heat. I pulled the armature and chucked it in my drill press so I could clean up the commutator. I used 600 grit emery cloth on a flat stick followed by 1500 grit and then the paper side of the cloth to clean up and polish the commutator. I put the new brushes in and fired it up. It seemed to run fine although there was sparking from the brushes. I proceeded to mow the lawn but after about 5 minutes of mowing the motor started to bog down. Now it runs very rough with lots of sparking from the brushes.
- Was there a basic flaw in my repair process?
- If so, what should I have done differently?
- Is it possible the brushes are not of the right type even though they are the correct size (e.g. not the correct composition of carbon for that motor type)?
Thanks in advance for your assistance.