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Aluminum Polishing Part IV - Techniques

Posted by Jay Schneider. Filed under Aviation.
April 5, 2011

There are several ways one can polish aluminum. They are: hand polishing, machine orbital polishing, DA (dual action) machine polishing, rotary polishing and drum buffer polishing. With personally spending thousands of hours polishing aluminum on an award winning North American Navion, I’ve seen and heard it all.

Hand Polishing. Not really a bad way to go. Pros? It’s inexpensive, good exercise, has less risks and provides a fairly good finish. Negatives? It is tiring, yields inconsistent results, it is time consuming and no risk on over temping the surface. Face it- polishing a large surface area similar to a grey hound bus with a 4X6 inch applicator is crazy for some but good therapy for others. The natural circular hand motions of Danielson’s “WAX ON, WAX OFF” lead to very low surface temperatures’, which is a concern when rotary polishing and yield very inconsistent results. The smaller surface area of the applicator along with varying hand pressures hinders congruent swirls. The end result? A mediocre shine.

Orbital Machine Polishing. We are moving up the ladder on this one. Orbital polishers have come a long way in the past 12 years or so. They are more powerful, compact, light weight and becoming more affordable. The electrical ratings on these machines can range from .5 amps to over 5 amps and have drive pads from 1” to 15”! The most popular versions today resemble 4” die-grinders that are light weight and powerful. However, scratch and heavy oxidation removal can be challenging for orbital machines.

Dual Action Machines. Dual action orbital polishers are a dual action polisher on steroids! These machines effectively remove swirls, scratches, and oxidation that can’t be removed using orbital polishers. The orbital rotation of the polisher simulates the circular movement of the human hand while polishing. This motion is less likely to cause holograms than a rotary buffer. At the same time, the polisher's highly smooth running facilitates a careful, precise finish. The positive drive ensures a uniform movement, even under load. The advantages – best of both worlds. You can have the orbital as well as rotary action in one machine. Disadvantage – more costly and limited backing plate size.

Rotary Polishers. These old timers have several advantages and disadvantages yet provide the user with the greatest selection pad substrates and polishing flexibility available. Advantages - the mere weight of some of these machines make it less fatiguing when polishing large horizontal surfaces, the rotational sheering force is great for cutting, compounding, scratch removal as well as heavy oxidation removal. (This is definitely my choice for polishing bare aluminum surfaces.) Pad material substrates are plentiful - from the lesser aggressive acrylics to more aggressive wools and polyesters. These newly designed yarns minimize swirls produced by the polishing process.  Different sized backing plates allow the user to get into smaller areas as well. The disadvantages – rotary polishers command more respect and are recommended for the more experienced machinists. Their rotation force can be very damaging and cause injury to its operator and or the working surface. Heat buildup is another detrimental effect from the usage of rotary buffers. Aluminum can be permanently damaged from too much heat where it will expand and not contract back into its original shape sacrificing structural integrity.

Pneumatic Barrel Buffers.  Not as popular with the novices, but the only way to go when you have a Boeing 737 to polish out! These monsters require massive amounts of air to turn their powerful air driven motors. Advantages – Powerful, long handled for high reaching applications, uni-directional – the drum turns in one direction eliminating swirl marks,) but leave parallel marks). Disadvantages – expensive. Commonly cost upwards towards $3,000. Limited in the number of polishing substrates available for use.

A very good choice would be to start out with a rotary machine and finish up with a random orbital. You’ll lose a little shine when finishing but the risk of swirls’ is greatly diminished.

Next up – going to work.

 

Keep the Blue Skies Up and Happy Motoring!

Scott

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