Dry Sanding Techniques:
If you are doing a lot of sanding duties, you should possible consider adding a power sander to your shop.
They can take a lot of the moronity out of the sanding process and in the hands of a skilled guitar finisher they can save a tremendous amount of time.
Be aware however, it is very easy to completely ruin a finish with one of these powered sanders.
The most common sort of power sanders are the random-orbit and orbital sanders. The DA sanders, which are air-powered, an much less common as they require a very large compressor to operate properly.
Ideally the use of powered sanders are most efficient when utilized in large flat areas. They will remove materials very quickly and it is very easy to over-sand and completely ruin the finish.
Random-Orbit sanders leave much less sanding marks or scratches as a result of using the sanders. Orbital sanders leave the most sanding scratches of any of the three outlined here.
You can hardly detect any sanding marks or scratches at all with the random-orbital type power sanders and thus you will find that you can use much coarser sandpaper as a result of this.
For the best results and fewest scratches, the Dual Action or (DA) air-powered sanders really shine.
Powered Orbital Sanders:
You may more familiar with the therm “vibrator” type sanders, as this is basically how these units operate.
They operate by means of an offset weight on the motor shaft, and this causes the pad to travel in a small circular pattern.
You will find that most of these type of sanders either have a square or rectangular shaped pad. The are also referred to as block sanders.
Normally the sandpaper is clipped to the bottom of the pads on these sanders.
Power Random-Orbit Sanders:
Random-Orbit sanders are a marked increase in value for those of us in the instrument building business.
They are the latest and greatest in sander technology with regards to the electric sanders and they mimic the action of the air-powered DA or Dual Action sanders that have be used for years in automobile body shops.
Even though the random-orbit sanders operate a bit like the orbital type, they sand in a small circular pattern.
In addition to the circular or orbital motion the pad also rotates slowly, which acts to remove any trace of circular sanding scratches.
The pad is prevented from rotating to fast in the sander mechanism, as this the integral to the success of the tool.
You will find the most common types of sanding discs by either hook-and-loop, which is basically a velcro system, or by pressure sensitive adhesives.
If you have a small shop, I would highly recommend a good electric random-orbital sander.
Air-Powered DA Sanders:
These sanders equally work very well on large flat surfaces, just as with the electric random-orbital variety.
One great feature of the air-powered Dual Action sanders is they can run at random speed, give you a lot of control in the amount of material that can be removed.
Naturally at the highest speeds the DA sanders will remove an incredible amount of material and you can sand through a finish in no time so you really need to be careful with them. Another great use of these sanders is to make quick work of rough wood.
It seems as though these sanders with the model that was used in the development of the newer random-orbit electric sander models.
One thing that you need to know about the air-powered models is they require a tremendous amount of air to run properly. An air compressor with a minimum of 3 horsepower or great would be required.
For a small shop this type of equipment will be very expensive and the noise that is generated by these large compressors is very damaging to your hearing. Therefore some distance and segregation is required for these big compressors.