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Old 07-13-2004, 06:12 PM   #1
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Post Comm Cutt'n 2

How important is it to CUT your comm, or better yet buy a comm cut'n machine? I mean, I took one of my motors apart last week and sprayed the inside of the can, bushings, armature, etc.., but when it came to my comm, I said "What the hell, I'm gonna try something...". So I grabbed a piece of scotch brite (very fine grit) pad and went to work. In about 5-10 secs, sprayed it off with motor spray and the comm looked as good as any machine job. So why is CUTTING the comm necessary?

Just a simple question, from a simple mind, wanting a simple answer

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Old 07-13-2004, 06:16 PM   #2
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The finish isn't important-it's the roundness that counts. A comm that has depressions in it is much harder on the brushes and they bounce.
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Old 07-13-2004, 06:18 PM   #3
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To answer your question: Not only does cutting the com "clean it" but it makes it round. You com will groove under the wear and pressure of the motor brushes as well as going out of round. A fresh cut restore the perfection that you will want out of your motor.
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Old 07-13-2004, 11:59 PM   #4
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Like the others have mentioned.....the shine has nothing at all to do with the roundness of a comm or performance of a motor....a properly fresh cut comm will help give you optimum power as well as getting you the most time out of your brushes......it's a very important piece of equipment , even if your just semi-serious about racing......even at most club races a motor with just 3 or 4 runs on it will not be up to par for top competition......Inbetween runs you can use motor spray and a comm stick.....It will do effectivly what you accomplished with scotchbrite, but even better, because you can do it with the motor still assembled and also clean the inside of the brush hoods with it....
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Old 07-14-2004, 12:21 AM   #5
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Just tonight I cut the comm for one of the novice racers. His armature was a prime example of why you need to CUT it with a lathe. I had to do about 5 passes because he'd never had it done before, and what was interesting is after 2 passes 1/3 of his comm was perfectly shiney, while the other 2/3rds hadn't even been touched by the bit yet. Keeping it round is why you need to use a lathe and do it right.
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Old 07-14-2004, 12:27 AM   #6
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yeah, take a look at the comm of a newbie's motor that hasn't been cut for 50+ runs and where you can actually see the difference in diameter on different parts of the comm, then you will understand why you need to use a lathe
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Old 07-14-2004, 02:06 AM   #7
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Also the more often you cut it the longer the comm will last. As they wear down more they also wear quicker. I do it before each race day.
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