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Chrome
Chrome isn't polished, it's cleaned. Unlike aluminum and stainless, chrome doesn't oxidize much, it's pretty inert, very hard, and usually pretty thin. If you find a "polish" that removes scratches from chrome, please let me know. It's been my experience that you have to live with a scratch in chrome, or replace the part.
If you're real careful not to scratch it, all you have to do is remove the schmutz and the shiny chrome will be underneath. Use soaps and solvents, but keep abrasives far away from chrome. Be very careful to use clean, soft rags, one imbedded metal chip will ruin your day and your chrome.
Aluminum and stainless
There are hundreds of alloys of both. What they all have in common is the fact that they oxidize at the surface. Fortunately, that oxide layer protects the metal from further corrosion. The goal is to remove the oxide, and get it smooth (that's the hard part). Do this properly, and the finished product will rival chrome in shine. Some prefer the softer look of polished aluminum. The advantages are ease of repair and costing less than chrome.
Smoothing
If the part is oxidized and gray, but smooth, skip to the "Buffing." section. If the part is pitted or scratched, it must be smoothed. One note: pits can't be polished.
Wet-sand the part with #600 wet-dry paper using a little liquid dish soap in the water. Sand for a while, wipe off the dreck, and examine closely. If you can see pits or scratches through the dark, dull gray, continue to wet sand. When there is a uniform, dull gray, it's ready to be buffed. Don't spend too much time with screw recesses and other hard to reach places. As long as the edges are smooth, those parts won't show in the finished job.
Buffing
The final polish on metal is accomplished by buffing it with a rotating wheel that has been loaded with a buffing compound. Buffing compounds are very fine abrasives, usually combined with wax in a bar form. From the roughest to the finest, they are:
Many people simply use emery and rouge. Emery is good for the initial cut on either stainless or aluminum where just a little more sanding is needed. Many times one can go directly from sanding to rouge.
Buffing requires a certain "feel". If the wheel is kept moving, you can see when it's polishing effectively. Occasionally wiping off the wax schmutz will allow you to see how much progress has been made. Different alloys require different compounds, speeds, and pressure. This is where the "feel" comes in. The typical user can't hurt anything, so feel free to experiment. Perfectionists may want to do a final hand polish as explained in the "Maintenance" section.
Wheels
Use only cloth wheels. Felt doesn't follow odd shapes, and sisal is too aggressive. Inspect the side of the buffing wheel and note the ring(s) of stitching. Fewer rings indicate a softer wheel, which should be used for polishing. More rings indicate a harder wheel, that should be used for cutting. A six inch wheel can have from one to seven rings. A harder buff should be used with emery, while a softer buff should be used with rouge. The rotating speed is dependant on wheel size. For a six-inch wheel, speed should be limited to 3500 RPM. A four-inch wheel can be turned up to 6000 RPM. A two-inch wheel can be spun at 12000 RPM. Wheels smaller than one-inch can be turned up to 15000 RPM. Always use the wheel manufacturer's specifications.
Wheels come with a number of different hole sizes, so the right mandrel or bushing will be needed. The mandrel is the steel shaft that holds the wheel, and is turned by the tool. These are available for electric drills, but the drill should be capable of spinning at 2000 RPM. Many drills are limited to 1200 RPM. It is important that the wheel be in balance.
You may want to start at slower speeds, and work your way up. It is possible to be too fast, as well as too slow.
You may also want to use the buff so that it rotates off the edge of the piece. If it rotates toward the edge, it will throw pieces at the operator.
Load the wheel by arranging it so the top is turning away from the operator. Next apply the bar of compound for a few seconds. The compound will melt in. After loaded a few times, clumps of the compound will build up in the wheel. Make sure the top of the wheel is turning away from the operator while the wheel is being raked. Wheel rakes are available, but an old sawsall blade will work as well. It is best to have one wheel dedicated to each compound. Mark each weel with a marker. If a single wheel is used for multiple compounds, rake the wheel between the application of each compounds. Words cannot express the imporatnce of wearing eye protection.
Tools
- An electric drill capable of spining two and four-inch wheels at 2000 RPM. Bosch drills that are capable of these speeds are available at many hardware stores, where the wheels are also typically available. The problem with two and four-inch wheels is they won' fit into tight spaces. It is preferable to use the largest wheel that will fit, as the smaller ones can streak.
- Dremel is a brand of power tool, but a Dremel "type" tool will work just fine. Black and Decker sells a similar tool for under $40. The Black and Decker tool will turn all Dremel bits and buffers, which are widely available. The low and middle speeds (12000 & 24000 RPM) will handle most work. The one-inch bufferss will fit most places, and there are small (3/8") felt bullet shapes that can be used to fit into screw recesses.
- A bench mount grinder with two 1/2-inch buffers on each shaft - a hard pair for emery, a soft pair for rouge. This is a great tool, but has limited applications. You'll have to disassemble the part, and bring it to the buffer.
Maintenance
As previously stated, the oxide protects the metal, so as soon as the polishing has ended, the metal starts to oxidize again.
Waxes have a tendency to gray the sheen, and don't last long. Spray on waxes are easily and quickly applied, but may require a weekly application.
© 2009 Marcus Blair Fitzhugh
Signal to Noise