Aluminum Polishing

Just wondering how to polish the aluminum cases and other small parts, from my bike. Is a bench grinder/buffer the best way?

If you want to re-polish an alloy part that was originally polished, the buffing wheel with some good polishing compound will work. But if you want to polish a cast part that was never tumbled (the original polishing process), you'll have to take it down with successively finer grits of sandpaper to get rid of the cast surface texture. Grind off any seams, sprue or other imperfections first, then sand with 50, 100, 200, 400, 600, 800 and then 1000 grit before using the buffer and compound. When sanding, use a circular, random motion and try not to leave any gouges, especially with the rougher grits.

Like Danno says, if it has previously been polished, you can get a 3/4HP buffer from Harbor Freight for about $80. You will need buffing wheels, go to the Caswell site, they have plenty and will explain it all. You will need black, red (rouge or brown) white, blue for stainless and maybe green compounds. Get a large bar of each. Wear a hat and eye protection and be prepared for grease all over your clothes from the polishing compound. Your wife will whine about the grease on the pillow from the grease that gets in your hair, if you have any. I have had good luck polishing AL with 80, 150, and then 320 with a DeWalt orbital hand sander. After that you can usually go right to the black compound and then finer, like red or white. You will need different wheels for each color. Clean the item between colors too. You will never get all the holes out of the AL castings in the Norton M/C. Only way to get a real mirror shine is to take it to a professional buffer person who will have probably a 6 HP buffer and will melt the metal to get it looking real sharp. I think after having done it, I would send it out and pay the bucks. But I had fun, I guess.

Dave
69S

You can match the best pro polishers with just a hand drill and buffer wheels, Ater you've done as Dano says,work down sanding grit, but I found to keep going to 1200 then 2000 grit before starting the 3 grades of polish and buffer wheels.
I mounted hand drill in vice and have at it. But BEWARE, polishing is medittaive tedius and puts one in a trace seeing the fine surface appearing, and about then the piece flings out of grip to ding surface and start all over again. Files can be handy to use before sand paper in some spots. The power need is to spin fast and hard enough to melt the carrier waxes, drill just takes longer is all. Castwells or Eastman has polish kits-supplies. Some things can be done so so on bike but most will need to be free in hands. Next issue is to avoid redoing in a year or less, so study up on waxes and clear coat wheel paint.

As final process I use the corn starch-talcum powder to wipe up wax out of pours then 'flame anodize' to burn out residual wax-grease carriers and melt over microscopic ridges and form a bit more sapphire surface layer.

There used to be a guy in the Norton club who would take his 750 Roadster down to nuts and bolts every winter and power buff all the polished alloy. Man that thing look fantastic, but that's way too much work for me.

You know something Dano, that is exaclty what I hope to do making love to Ms Peel cured up next to a warm fire place flickering flames glinting off the smooth curves and angles, warming to my touch, pressing harder - well you know, or why would know so much about it, eh?

hobot'r and out.

You can match the best pro polishers with just a hand drill and buffer wheels, Ater you've done as Dano says,work down sanding grit, but I found to keep going to 1200 then 2000 grit before starting the 3 grades of polish and buffer wheels.

Click to expand...

Although your results certainly speak for themselves, I've found that drill polishers simply don't have the surface speed and torque to do the job. If you're sanding to 2000 grit then hand polishing would probably do as well.

This shop made buffing/grinding station has served me well for 25 years or so. I use 8" buffs. Note the full face shield hanging on the wall - a wise man once told me, "Never buff anything that you're not willing to be hit in the head with".

Yes, how to beat having real power on surfaces. I put money in parts and spend more labor for the shine. Maybe my result have to do with going to 2000 grit paper.
Alas once even so so polished like me, the parts must be handled with kids gloves
and will decay by air and time alone, darn it.

That's why over the years I have selectively chromed parts on my bike. Much easier to keep up than polished aluminum. The major cases (primary, timing, gearbox) will always stay aluminum however, and require frequent attention. There's really nothing out there that lets the shine through and protects against time and air.

We've done a lot of aluminum buffing in the shop this last 2 years and one thing is real clear - you want to put a lot of time into the prep before the part ever touches the wheel. If you start with very coarse sandpaper, be careful that each time you go to a finer grit, you get the scratches out that were left by the coarser paper - if you left some 100 grit scratches in the aluminum, it won't matter how long you sand with 1200 grit - you want to get those scratches out with 150 grit or whatever you used after the 100 grit.

We use wet-or-dry paper for most of the sanding - if you sand with water it'll sand finer than dry - and if you sand with oil it'll sand finer than with water. Also - this shd be pretty obvious - the more you use a piece of paper, the finer it'll sand, as the abrasive wears down.

Files are handy sometimes - an 8" mill bastard file is a good size - you can blend some scratches and nicks out. You need to be careful with this - if you make a flat spot and then polish it, you'll see it in the reflection.

We're buffing with a 3/4 hp buffer and 10" wheels, running at 1800 rpm - I guess if you have a single-speed buffer you'd want about 6" wheels for 3600 rpm. It's pretty easy to find charts online that discuss surface speed of the buffs for different materials. We usually start with tripoli (brown) unless we have some really heavy buffing to do, then we go to "white rouge". Sometimes I've finished up with jewelers rouge (red), but I can't say that I see a tremendous difference when we do it.

Look out for areas that are hard to get to - sometimes you tend to work them real hard to try to get them to shine - then afterwards you find the the buff has taken away enough so you can see "grooves" in the aluminum - looks nasty when it's shiny.

Then put the stuff back on the bike - and everything else looks old because the aluminum is so shiny <s>... But take heart - after a few months of riding the aluminum will oxidize and won't be shiny anymore <lol>....

Ugh, too true pt. I also get grit-dust blasting dullness, and must use care to wipe off or might as well left it alone. I want to try anodizing or clear powder coat.
Sapphire as in scratch-less watch lens is Al oxide, same as anodized Al surface.

http://www.mini-lathe.com/anodizing/ano ... uminum.htm
Simple clear anodizing is surprisingly easy, zap
it in acid and pitch it in boiling water. Adding color is where it
starts to get hard. Fortunately I like shiny stuff, so I'll be doing
most of my personal anodox in clear over polished aluminum. Here's some
links to a couple of places that sell the stuff:

If you haven't done it before find a local polisher to do it right. The buffing wheel can take your part and fling it across the garage before you even know what happened. If you can find it there will be a ding in it that will make you cry.

If you choose the hand drill route, the buffing pad can suddenly slip off sideways and your drill chuck will be grinding away on the part being polished. Not all that good.

It seems simple but it's not. Not just me - I know I can be spazzy already.

batrider knows what he's talking about and knows excatly how's its worked out on my hand drill learning curve. If money no issue or more time than money or use want your own surface to show, hammers then files then paper to finest grit you can get then grades of polish compound by 6" hand drill in a vise or stand, can equal a pro's after a very short bit of exposure to riding or storage. Its a test of concentration and physics of forces vs fine muscle control or 1st instant attention wavers, zing ping pong, pranged. Parts should get pretty darn hot to handle but gloved hands may allow a slack grip or slips of aim > for tank tracks of drill head across otherwise lovely fine finish : (

Darn Amals will shiny up but not get much brighter d/t zine alloy dull grayness.
Not good to polish much heat dissipating areas as reflects IR heat back in as much as visible light back out to eyes.

Plastic items like some buffer wheel attention too. Clear coats can be rubbed down or wheel polished too, ohh laa laa, just saw Trixie's yellar parts tonight, shiny as can be even better painter applies finish buffing,

I'm going to try to polish out thumb size rim rusts on Trixie to leave a shiny area then wax over and hope few notice - being distracted by other glitter : )