Aluminum polishing

[spyder_xlch]

SANDING
Using 40 grit will take off the rough sand cast finish and remove the casting ridges. Move up to 80 grit. Use 120 grit for any blemishes in the aluminum. Do the same with the 180 grit. Step down from 180, 240, 320, and 400 to get the metal smooth enough for final polishing. If there are no blemishes skip right ahead to 320 grit wet sand and then 400. Stop at 400 grit paper. At the most you want to go up to 600 grit but only briefly. The high grit sandpaper creates too many tiny pores. The pores are too small to get all of the crap out. Let the polishing compounds do the rest. At most use a super fine #0000 steel wool but briefly. The scratches left behind from the 400 grit will be smoothed out by the compounds instead of scratched out with the sandpaper.

BUFFING
Make sure you have a consistent 400 to 600 grit finish on your aluminum part before you start. Any scratches or imperfections visible will still be visible after polishing, it will just be a shiny imperfection. You must use different wheels for the different compounds. Keep at room temperature or warmer. The rouge will goop up if the part gets cool. Use a heater to keep the parts warm.

Cut Buffing-
This is the preliminary step to “coloring” using a course buffing compound. Black emery polishing compound with a spiral sewn buffing wheel is recommended for cutting down copper, brass, aluminum, steel, stainless steel, nickel, and iron. Gently put the stick of compound against the rotating polishing wheel for a few seconds to transfer the compoung to the wheel. Brown tripoli buffing compound is not as course as black emery polishing compound but will cut and color copper, brass, and aluminum in one operation. Cutting down may produce a bright, satisfactory result and coloring may not be necessary. Don't push so hard that the wheel slows down a lot. Be careful, the wheel will grab unexpectedly and can propel the part or the drill across the room. The polishing wheel will also grab onto sharp edges, so go easy. Mounting the polishing wheels on a bench grinder is an option that works well but there are times when the drill mounted wheels are easier to maneuver. Reapply the compound every couple of minutes. Keep going over the part until you get a good shine. Use a Dremmel tool with a conical shaped felt bob to polish the hard-to-reach areas.

Color Buffing-
This buffing operation brings out the maximum shine and produces a mirror like finish. Coloring can take place after “cutting down” or right-away if surface is smooth enough. Loose cotton buffing wheels are usually the best choice for coloring but spiral sewn buffing wheels can be used as well. Brown tripoli buffing compound is a double duty buffing compound and can be used for both coloring and cutting down. White rouge can be used to color chromium, stainless steel, brass, and aluminum. The finest buffing compound is Jewelers rouge a.k.a. red rouge and can be used to produce a mirror like finish on gold, silver, sterling, platinum, and brass (not aluminum). When you use a polishing wheel after it hasn't been used for a few hours you must "comb out" the wheel by rubbing it against a wire brush. Felt polishing wheels and Felt Bobs are made of compressed wool fibers and work with all compounds and are great for getting into hard-to-reach areas and removing residue left from buffing.

There is an even better and finer polishing compound out there if you want to go one step further. India Ink has carbon in it and it is extremely fine. Use Chamois and india ink and keep rubbing. It requires hand rubbing or you'll have a serious mess and, requires rubber gloves. When you can't get any further, dilute the ink in half and continue the same process until you can't go any further. Dilute in again one half and repeat the same process. You'll get a mirror unmatched. You could continue to dilute it and refine the mirror but you'll end up with no time to show off your work. If you keep the part clean, then using the diluted ink every now and then will maintain that mirror shine.

Compounds, course to fine
Black Emery, Brown Tripoli, White Rouge, Green Stainless, Jewelers Rouge, Blue All Purpose

Mothers mag and aluminum polish or Wenol contain anhydrous chemicals, they attack aluminum, mag and zinc. They cause oxidation.

[Musicman]

Wow, thanks for the info. Good job