polishing aluminum - what do the pros use?

Dunno what the pros use but I re-polish my alum truck rims with Nev-R-Dull magic wadding. Best I remember, my last can was bought at a CVS drugstore.
technomaNge
This is a nice NG once I got all my kill filters set correctly.

I've used Never-Dull before and it works pretty well but I dont know that I would put it above Flitz or any of the other polishes I have used. I was thinking maybe there are various grades of jewelers rouge or some other more industrial grade products that would get me the mirror finish I'm after.

You need a buffing wheel and a stick of jeweler's rouge. You have to apply the rouge heavily to the buffer and then jam the workpiece hard onto it so the work and rouge get hot. When you smell hot Carnauba wax you are getting there. You may literally have to hold the work with gloves to avoid burns. When the wax is hot enough to be near liquid the rouge is able to flow and expose the surface of the tiny particles that do the work. Wear a dust mask, or you'll be blowing black crud out of your sinuses for a week.
I worked on polishing an 18' radar dish into a solar collector, and we tried a bunch of "easy ways out" before finally getting a really GOOD polisher and doing it the "elbow grease" way. You can use a buffing wheel and bench grinder motor due to the small size of your part, and that will make it a lot easier. (The monster 1 Hp buffer we used after burning up a cheapie was a very heavy industrial grade machine, and it really tired your arms out.)
Once you get the setup put together and the buffing wheel loaded, it will only take a couple of minutes to do one square foot, from rough sandpaper finish to mirror polish. You will NOT get a real mirror, however, due to uneven material removal and warpage. If you want it totally shiny, this will work fine. if you want an optical grade, first-surface mirror, it is a LOT harder to keep from having inch-scale waves in the surface. (That's not inch-DEEP, I mean tiny waves of maybe .010" deep repeating every inch or couple inches. Very careful attention to keeping the buffer moving evenly and making each pass at right angles to the last pass will help some, but you can't avoid this patterning with freehand buffing.)
Jon

On Wed, 21 Dec 2005 19:01:26 -0600, with neither quill nor qualm, "mike" quickly quoth:
All my buddies with motorcycles swore by (not at) Mother's Mag polish.
--== May The Angst Be With You! ==-- -Yoda, on a bad day -- Ending Your Web Page Angst.

If by "mirror finish" you mean high distinction of image rather than optically flat, you're almost there.
Flitz, Mother's etc can't make a finish better than it was, they only restore finishes by removing oxides and tarnish. You're trying to create a finish that didn't previously exist.
If you just want it "shiney", then a buffing wheel and tripoli buffing compound will get that done very quickly. Some will say rouge (white or red) but I think tripoli works better on aluminum, though a light hand-buff with white rouge and a cloth can sometimes give the final coupe-de-grace -- that'll last about 15 minutes before the ali starts to dull from surface oxides forming. How good your finish can be will depend some on the aluminum. Some aluminum alloys accept a higher polish than others.

You should be able to find a product called SimiChrome. It's a paste that will do what you want to do unless you are looking for an optical quality finish.

Well, acording to our friends at NASA, India Ink!

After a single-point diamond turning. Where are these tools available, BTW?

Here is one source:

I really like Mothers Aluminum Polish, sold in many auto parts stores.

What do you mean by "mirror" ? Shiny, or reflect your face in it? If you want shiny it's easy, if you want a perfectly flat surface as well that's harder.
I'm assuming you just want shiny. This is pretty easy and you can do it all by hand for little money. You can use power tools if you want, but aluminium is pretty soft and the better controllability of doing it by hand will be quicker than fixing high-speed slips with a power tool.
Go to the shop and buy a set of "Garryflex" blocks (UK brand - there'l be a local version) These are big rubber blocks, filled with grit. They're colour coded and come in different grit grades. Get a set of all of them.
Now work the big grits first and work carefully and methodically over the whole surface. Support the piece (if it's sheet) on a layer of old carpet or blanket on a wideworkbench - you don't want to drop or bend it. When you've worked the whole piece with one grit, go down to the next grit and start again. Work clean - wash your hands and the workpiece between grits.
It's dead easy (and quick) to get a mirror shine. The hard part is getting one that doesn't also have scratches in it. Don't rush into the finer grits - a big scratch needs a big abrasive to remove it, even if this makes a lot of smaller scratches in turn. getting out those few big ones will take twice as long as putting that first mirror onto it did. So that's another reason to work from clean unscratched sheet in the first place and to be careful when you're working - don't use dividers on stuff you're going to have to plate or polish afterwards.

I appreciate all the advice and knowledge here. Here is a picture of what I am trying to accomplish. I might consider subbing it out to a local metal polisher if it isnt an arm and a leg

Mike

Oh, right, engine parts.
Add another £100 for a Foredom or similar machine with a flexible shaft and £50 or so for the numerous felt bobbins and compounds you'll be needing to reach into the corners. OTOH, you'll not regret owning the Foredom afterwards.

Am only wanting to polish the outside flat areas. I didnt think it would be that hard but now am a little concerned that this particular cast ali cant be polished to the sheen of the valve covers.

and sand in one direction -only-.
Which is the trick to sanding down to the near mirror finish that will just need a polishing it up to a real shine.

Umm, the diamonds themselves are not terribly exotic. The MACHINES, however, are extremely exotic. Many of them run under a complete deluge of water held to .01 degree C, to keep all parts of the machine from thermal expansion, as well as the workpiece. These machines usually use laser interferometry for position measurement accurate to a few nanometers. A nm is 3.9 x 10^-8 inches, or 1/400 the wavelength of blue light. These machines cost several million $ each, and there are, at best, a few hundred in the entire world.
Jon