Cutting comms

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Old 07-08-2006, 10:22 AM
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Default Cutting comms

I have been cutting comms for 3 years with my trusty Hudy lathe and diamond bit.

My process involves: 1) marking the comm with Sharpie; 2) cutting until I get a smooth comm; 3) using Xacto knife to clean gaps between comm plates; 4) using ballpoint pen to smooth edges between comm plates; and 5) using motor spray and towel to clean (and shine) the comm before reassembly.

Someone (that I have great respect for) told me that using motor spray and the towel are no-no's...That the motor spray adds a lubricant which is not desireable for brush break-in.

Any comments?
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Old 07-08-2006, 10:26 AM
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Motor spray wont hurt. Thats why its "Motor" spray. I dunno about a towel though as it might scratch the comm but if you've been using it with sucess it shouldnt matter. I tend to hold the arm upside down and spray the bottom of the windings and keep spraying until the runoff is clear.
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Old 07-08-2006, 10:41 AM
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Thanks rcdude.

The black residue that comes off the comm after the other steps had convinced me that using the towel was a plus. Some of that black is likely the Sharpie material getting between the comm plates. Always looks brighter after.
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Old 07-08-2006, 10:53 AM
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Do you use comm cutting oil? Seems like if lubricant is a problem, you'd rather get that off first.
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Old 07-08-2006, 11:16 AM
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Originally Posted by syndr0me
Do you use comm cutting oil? Seems like if lubricant is a problem, you'd rather get that off first.
No comm cutting oil here. I understand that the black graphite in the Sharpie ink is a form of dry lubricant though.

Guess that is what I am asking...Is any lubricant on the comm (i.e. spray, drops, Sharpie, etc.) detrimental to breaking in the brushes?

One other practice I have when I don't cut the comm is to spray the assembled motor out and relubricate the motor bushings. Good/bad?
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Old 07-08-2006, 11:17 AM
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I do all the steps you mentioned above, but use a Red Sharpie & a paper towel. After i cut the comm I take it out of the lathe and spray with electronics cleaner from the windings towards the comm slot's.

I then put it back into the lathe to spin out any excess "junk" and then use a comm stick to polish the comm. I spray the paper towel with a little motor spray and clean off the tip of the comm stick first.

Then I take out the comm and spray out the slot's one more time to clean out any residual comm stick "dust"..... the shake off the remaining motor spray and put the motor back together.

my 2 cents
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Old 07-08-2006, 11:27 AM
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Originally Posted by tbeardmore
I do all the steps you mentioned above, but use a Red Sharpie & a paper towel. After i cut the comm I take it out of the lathe and spray with electronics cleaner from the windings towards the comm slot's.

I then put it back into the lathe to spin out any excess "junk" and then use a comm stick to polish the comm. I spray the paper towel with a little motor spray and clean off the tip of the comm stick first.

Then I take out the comm and spray out the slot's one more time to clean out any residual comm stick "dust"..... the shake off the remaining motor spray and put the motor back together.

my 2 cents
Interesting. But, I believe that a red Sharpie has no graphite content...

My comm comes off the lathe pretty nice looking. A little spray and towel (paper or cloth) are my finishing touches.

So, you don't use a knife or ballpoint pen for between the comm plates?

Thanks.
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Old 07-08-2006, 11:29 AM
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Uh oh! Smash is in the house...
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Old 07-08-2006, 11:36 AM
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Bill- I use a burnishing tool on the comm slots. You can find them at arts/crafts style stores with a variety of tips...

Last edited by J.Filipow; 07-24-2008 at 08:51 AM.
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Old 07-08-2006, 11:39 AM
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Originally Posted by J.Filipow
Bill- I use a burnishing tool on the comm slots. You can find them at arts/crafts style stores with a variety of tips...
J

Now, that looks like a nice improvement over my Xacto knife. Gonna hit the hobby shop for one before I get to the track this afternoon. Thanks.

What do you think about the motor spray issue?
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Old 07-08-2006, 11:52 AM
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Originally Posted by tbeardmore
I do all the steps you mentioned above, but.....

Read first....
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Old 07-08-2006, 11:55 AM
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Originally Posted by JRX-S Bill
J

Now, that looks like a nice improvement over my Xacto knife. Gonna hit the hobby shop for one before I get to the track this afternoon. Thanks.

What do you think about the motor spray issue?
I don't see any problem using it, motor spray is suppoed to leave NO residue, so it should be ideal for getting any stray lubricants off the comm surface, & as long as the towel you use to wipe it off is clean, I don't see a problem there, either(in fact, I use both exactly the way you do, every step of it, & it's worked fine for me for many years)......
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Old 07-08-2006, 12:02 PM
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Pretty much appears that we are on the same page.

Headed to the track (Ripon) in a couple hours.

Thanks all.
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Old 07-08-2006, 12:53 PM
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I find most of the "gunk" comes from the ink in the ball point pen itself. I typically cut the comm and round the edges with the ball point pen between passes also cleaning the groves with an exacto as I go. Before the final pass I round the corners with the pen and skim the comm for the last time. Clean the groves out with the exacto and use a blend of Methanol (or methal alcohol) (Ethanol is better and leaves no residue but is difficult to get unless you have a liquor licence. I know the Calibration labratories use Ethanol for zero residue cleaning) and Acetone. Isopropanol (or rubbing alcohol) works as well but leaves the most residue. This is an excellent solevent mixture and takes all the ink, etc out of the comm. I use lint free wipes (eg Kimberly-Clark, etc). Once the comm is cleaned I use a pencil type eraser (no ink eraser!) to polish the com to a mirror finish the clean the groves out again and a final wipe.....
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Old 07-08-2006, 08:23 PM
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I got three cents on this one:
Way back when..I usta do VCR head cleaning and read where all cleaners leave a residue. Although very minute, they ALL laeve something. So, it seems to me that for the absolute A-nul (This means ME) No claener should be used after the final cut. Remember, this is refering to the space between the head of a VRC and the tape, as it plays, So we are talkin' very fine layers. I don't remember which unit of measurment was used but it was tee-niny. Age has a way of erasing detalis.
POD
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