At a MK1&2 Jaguar workshop being held at Sid Robinson's I produced a some SU carburettor parts to illustrate the point about SU diaphragms which included a dashpot which I had polished. This dashpot seemed to attract a lot of attention and the question was asked " where had I got the polishing done ?".
The answer was I did it myself in a few minutes with a relatively simple and cheap buffing machine on my own workbench. I had learnt a little about metal polishing from a professional in the aviation trade many years ago and applied it for my own purposes.
Most of us admire the concourse cars' engine bays with those beaut polished alloy cam covers and carbys etc. without realising that we can achieve quite good results without resorting to expensive professional treatments.
My own buffing machine consists of a six inch [150mm] bench mounted grinder which has had the emery wheels removed. These grinders vary considerably in price and I have seen them as low as $29 but expect to pay more like $50 to $70 for a reasonable quality item.
I have attached a six inch wire wheel on one side. Once again these vary in price but average about $15 to $20. You don't need the wire wheel for polishing but it is a boon when removing old paint, rust, scale and all the other rubbish encountered when involved in Jaguar restoration.
The other end has a spindle screwed onto the shaft which mounts the cloth polishing wheel. Note that the standard bench grinder has a left hand thread on the left hand side and a standard right hand thread on the right side. This acts as a self tightening system for the nuts retaining the emery wheels, so when purchasing a spindle ensure you get the correct thread for the side you intend to mount the polishing wheel. Spindles cost typically $15 to $20. The six inch cloth polishing wheel is simply screwed onto the spindle. Once again prices vary depending on grade and quality and somewhere between $10 and $20 should buy one.
Finally you will need a compound stick sometimes referred to as jewellers rouge. This is the actual material which will do the polishing. They come in a number of grades and some assistance should be sought from the retailer on suitability for alloy etc. Most cost about $5 to $7 per stick. I am currently half way through a stick after 2 years of use so it does go a long way.
Before you launch into polishing with this setup there are a few things you should know about the nature of the material you are going to polish. Cast aluminium alloys can be surprisingly porous and do corrode. Have a look at the effects of corrosion on old thermostat housings and cylinder heads
If the aluminium you intend to polish has a lot of black embedded in the surface that means you have a case of corrosion and you should take steps to remove this corrosion which will be embedded in the surface of the material. There are a number of commercial alloy cleaners on the market and you should investigate the use of one of these. A good source of supply is from truck specialist shops who sell this cleaner for use on alloy truck trays.
Another way to get rid of corrosion is to use of "wet and dry" or emery paper. You can quite easily rub the surface back to a clean "white" finish. If you don't have this sort of finish it is a waste of time going on with buffing unless you are prepared to resort to heavy grades of compound stick to cut the corrosion out of the surface. I would not recommend using anything coarser than 280 grade paper and work back up to at least a fine 600 grade paper before attempting to polish with the buffing machine. Another useful trick on large surfaces such as cam covers is to use an orbital sander with these grades of paper - it sure saves a lot of elbow grease.
Now before you get stuck into polishing with the buffing machine lets get in a few words about SAFETY. All machinery is potentially dangerous and requires due care, attention and protective measures when being operated. Please read the manufacturers recommendations before operating a bench grinder. In addition the following recommendations should always be followed.
1. Wear protective goggles. Bits of hot buffing compound in the eye are not funny.
2. Wear gloves - preferably leather to protect your hands from hitting the wheel and remember the items being polished will get hot from the friction of the buffing wheel.
3. Don't wear loose clothing including scarves and ties. A pair of overalls with the sleeves fastened is recommended.
4. Be extremely careful when polishing small objects or pieces of sheet metal as the wheel may flick them out of your grasp. If possible mount them onto something larger on which you can retain a good grip
Warning. The professional polishers use large wheels [up to 12 inch diameter] with very powerful drive motors. If you do have or can get access to such equipment be very careful and get some proper training in its use. You will find that the six inch system I have described is relatively safe and in fact the typical 1/3 hp motor can be stopped by excessive pressure on the buffing wheel.
To actually use the buff simply turn it on. Allow the machine to come up to full speed. Hold the compound stick against the buffing wheel to allow it to pick up a thin layer of compound. Hold the object to be polished against the wheel and work it around. As the compound wears off reapply the stick. Finally, be patient and take your time as you are acquiring a new skill and will need some practice to get it "right". The process you are using is fairly slow and the light equipment means it will take time to get a good finish.
You will notice that the object you are polishing will get a build up of black "gunk" which seems hard to remove. This is only the residue of a combination of metal polished off and used compound which contains a wax. Any number of solvents such as petrol, turps etc will remove this.
As a last point you might like to experiment with this buff on some old chrome. I have achieved surprisingly good results in repolishing old chromed items including hubcaps, headlight rims, trim strips, acorn head nuts etc. Practice on some old parts if you can before attacking bits of your best Jaguar.