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My engine is all apart and I plan to polish the alternator cover and a couple of other bits. I was planning to wet sand the parts with 180 or 220 grit to get rid of any corrosion and then start buffing with the white compound using my drill press. I have 6 inch spiral bound buffing wheels, plus a dremel with bits for hard to reach areas.

I've done a little polishing before and I always seem to get black specs on the work. Any suggestions on how to avoid that? I also have black compound but I've never used it for fear of being too coarse.

Should I clearcoat when I'm done or will it not withstand the heat?

Thanks in advance,
Shawn
 

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smbevma said:
My engine is all apart and I plan to polish the alternator cover and a couple of other bits. I was planning to wet sand the parts with 180 or 220 grit to get rid of any corrosion and then start buffing with the white compound using my drill press. I have 6 inch spiral bound buffing wheels, plus a dremel with bits for hard to reach areas.

I've done a little polishing before and I always seem to get black specs on the work. Any suggestions on how to avoid that? I also have black compound but I've never used it for fear of being too coarse.

Should I clearcoat when I'm done or will it not withstand the heat?

Thanks in advance,
Shawn
If you're going to use 180 or 220 to get the oxidation off then you should follow it up with 400 and then maybe 800 to save yourself some time. Trying to polish out the scratches left by 220 grit will take forever on the buffing wheel, especially if you've got it mounted in a relatively slow turning drill press.
 

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I recently started doing the cleanup and pre-polishing work with 3M Roloc Scotchbrite discs. Get the fine and ultra-fine ones from an auto body supply place, maybe some medium if you have really ugly stuff to clean up. You can get the mandrel at Lowes for about $6 but they only have the coarse and medium discs. Thinking of grinding up 2x4s I guess. Sears also has them. I use the 2" mandrel and it also works just fine with 3" wheels. Works best with a die grinder but a drill can also get it done.
 

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I worked in an aluminum fabrication/welding department and went through hundreds of boxes of the 3M Roloc Scotchbrite discs a year. I wouldn't recommend using them for pre-polishing work as you have to be pretty careful or you can leave some pretty major scratches and/or gouging in aluminum with them. Yes, I have used them on motorcycle parts before and had a hell of a time polishing out some of the scratches left by those discs.

Being ultra careful may save you this headache but if you're not then plan on polishing for a loooong time after using them. If you use them on other material first and get them to the point where they're almost worn out then they do a much more gentle job on cleaning up aluminum, but when they're new they can and will put DEEP scratches in any aluminum alloy. You can almost cut thin aluminum with them. They're much more abrasive than you think because of their stiffness.

We used the ones shown in the middle/bottom of this picture, and thousands of them per year. Hundreds per week.



There, that's my warning to you all.


GB :mrgreen:
 

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I wet sanded with 800, then 1200 and used a Mother's Polishing Ball and Mother's mag and aluminum polish. It works awesome and easy. As far as clearcoating the parts, I don't know if automotive clear would stand up to the heat, maybe it would, but I bet you could get them powdercoated clear. That stuff gets baked on to set it, so you'd think the heat would only do it good.
 

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Bird76Mojo said:
Those are the coarse and medium discs. I found blue (fine) and gray (ultra fine) at the body shop supply place. You do have to be gentle but they'll get the heavy work done in a hurry, then use 800/1000 before the polishing. But then the stuff I was working on was pretty gross to start with, as Bird says, if its decent (previously polished) to start with even the ultra fine would take you backwards.
 

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Rush, as far as powdercoating being used on engine components, all I can say is that powdercoated parts, exposed to heat for long periods of time, or over several years, the original color will dull somewhat. Midnight black turns to a faded looking black, blues get lighter colored, etc.. Not extreme but noticeable if you compare them to the original color..

One thing's for sure. I miss working in the last factory I was at. Having access to a blasting booth with all types of abrasive, large enough to drive a semi into was nice. Not to mention the free access to a human operated powder booth and a multi-million dollar fully automated powdercoating line..

As for the abrasive discs, the blue/grey ones sound like a good option for removing the old yellow clear coats on engine cases, etc. As long as the user is careful during the process. I just used aircraft stripper on mine and what little was left of the yellowed clearcoat I removed with my bench buffer while polishing. It burns off and smokes something awful..


GB :mrgreen:
 
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