If you are not familiar with the properties of this metal, polishing machined aluminum is usually a process if trial and error. While it will never have a truly chrome-like finish, you can polish machined aluminum to a very clear reflection right in your own garage. One of the disadvantages of polishing machined aluminum is that, over time and with the exposure of elements, the aluminum will start to lose its luster. This can be corrected, however, by using the same type of metal polish that you use to clean and polish aluminum wheels.
Machining Methods: Polishing Compounds
Polishing compounds can be used to polish machined aluminum that appears to have no residual texture left over from the machining process. They are ineffectual on brushed aluminum. Polishing compounds work because the liquid or paste carries microscopic bits of abrasive compounds available that will polish aluminum, ranging from haze polish to scratch remover, and several intermediate grades of polish in between. Using polishing compounds is as easy as choosing the right compound and then rubbing it on the machined aluminum with a buffing cloth.
Machining Methods: Sandpaper Polishing
Sandpaper is a kind of polishing media that is useful if the machined aluminum you are working with has a pronounced texture to it. In general, sandpaper rated at a greater grit than 800 works well for polishing machined aluminum. When working with sandpaper, it is important to remember that adding water between the aluminum and the sandpaper acts as a lubricant, effectively increasing the polishing ability of the paper. For instance, if you polish a piece of aluminum with sandpaper up to 3,000-grit paper, simply sprinkling a little water on the aluminum before continuing will increase the grit of the paper you use.
Machining Methods: Lap Polishing
Machined aluminum that is to be polished to a perfectly flat surface should always be lap polished. A lap polisher is a machine that uses polishing compounds and smooth abrasives to achieve a perfectly smooth finish that is not possible when hand polishing machined aluminum. The drawback to lap polishing is that, generally, only one surface of the machined aluminum part can be polished at a time, then the material has to be turned to perform the polishing on another side. Lap polishing is also less effective at polishing complex surfaces and concave surfaces.
Machining Methods: Media Blasting
The method of media blasting when polishing machined aluminum picks up where lap polishing leaves off. While this kind of polishing is not very good for polishing flat surfaces intended to have a mirror finish, it is very good for polishing complex surfaces and concave surfaces. For the media blast to polish aluminum, it is best to use the smallest plastic media you can find. Glass and sand are too harsh and will actually dull the surface that you are attempting to finish.
While you can do any of these methods in your own home; it would probably do you better if you hand this job over to a professional, especially if you have little experience with machining. Contact a reputable machining San Jose company in your area to get started.