Aluminum polishing screwup

[Skinner]

So I made a bonehead mistake today. I was polishing the clutch cover and it was looking really nice. I then noticed several of those small “snail tracks” that happen when contamination gets under the clear coat. I was too impatient to just keep on buffing so I grabbed some steel wool and a sanding block. I got rid of the snail tracks but created more of a mess with all the resulting scratches. So I went back to the buffing wheels. First red for a while, then white. But the scratches aren’t going away. So what’s the correct way to take care of this? I have a sisal wheel, all colours of polishing compound and a few buffing wheels. I’m assuming it’s just going to take some time, but what colours should I use and in what order?

Cheers!
K

[posplayr]

You have to work your way down to 1500-2000 grit.
That steel wool cut some pretty deep groves that have to be sanded down or use a whole lot of polishing.

[Cipher]

400 grit silicon carbide wet dry paper then shift to 800 then 1000 then 2000 soapy water and rinse alot

[Sam 78 GS750]

Red is finer than white, so you were going in the wrong order. Different manufacturers of polish will have slightly different "grit" for each of the colors, but the order is always the same.
From course to fine: black, brown, white, red...
You can take out a lot of deep scratches with brown on a sewn cotton wheel, so start there and polish for a bit. If it's not taking out the scratches to your satisfaction go to black on a sisal wheel, and then back to the brown. After that, white on a loose cotton wheel. That looks really good, but if it's not pretty enough for you, you can go to red as a final polish.

[Nessism]

When polishing I use a sisal wheel and black compound and that's where I stop. The resulting finish is brighter than the OEM look. Do you want the cover to look like chrome? If so, then switch after the sisal/black combo to a stitched wheel and a white compound next. It's all up to you and what look you are trying to achieve. If you skip ahead too fast, skipping the sisal/black combo for example, you may not ever get the scratches/corrosion out.

[Skinner]

Thanks for all of the replies and suggestions. I sanded the piece with 800-1500-2000 then polished with red and it looks much better. There’s still room for improvement though. Thanks also for setting me straight on the colours.

Cheers!
K

[azr]

Good info everyone, thanks.

[Sam 78 GS750]

Thanks for all of the replies and suggestions. I sanded the piece with 800-1500-2000 then polished with red and it looks much better. There’s still room for improvement though. Thanks also for setting me straight on the colours.

Cheers!
K

You really can skip the sanding and save yourself a lot of time and effort.

I made the same mistake when I was first learning how to polish with a buffer, because I had only ever polished metal by hand with sandpaper.

For what it's worth... It took me a couple of hours to do my first engine cover, but by the time I got to polishing my fork legs it prob took me 20 minutes each leg to go from oxidized and scratched up to a mirror finish.

As Nessism said, black compound on a sisal wheel will get rid of corrosion and some deep scratches and looks great, even if you stop there.

Brown tripoli will also cut and get rid of scratches and corrosion, and after much trial and error in my process is where I usually start now for most pieces. I'll go down to black on a sisal if brown's not getting all the scratches out.

The only reason to sand is if you have some deep scratches or gouges in the metal, and you would only need to sand around those spots.

[Skinner]

Slightly off topic, but nonetheless...

I just purchased two 8" buffing wheels. My bench grinder has a 1/2" shaft but the wheels have a 5/8" bore. Any suggestions for adapting? I was thinking of cutting some small lengths of 1/2" copper pipe and using them as shims.

Cheers!
K

[Cipher]

CT or Princess auto not have a mandrel adapter kit?

[Skinner]

CT or Princess auto not have a mandrel adapter kit?

I bought them at Princess - no adapter kits at all.

[Skinner]

A couple of 5/8” OD x 1/2” ID x 1” bronze bushings did the trick.

[80GS850GBob]

Any time you find scratches, try and use the least aggressive sanding grit you can to loose the offending marks. Better a little elbow grease there than a lot of added sanding later to remove the marks you made to remove the original marks...you know what I mean...

[Skinner]

...you know what I mean...

Unfortunately yes.

[Nessism]

A sisal wheel and black cutting compound will take out DA marks made with 220 grit sandpaper.