Air-powered sanders have several advantages over their electrically driven cousins. They are smaller, lighter, quieter, have less vibration, and are safer in operation than electrically driven versions. They are also comparably priced, while offering similar performance. When working in an environment where flammable fluids and vapours are present, air-powered tools do not present the same risk as tools with arcing at the electric motor or switch.
Production woodworking shops use these sanders for their fast cutting action, which helps shop productivity, and for their ability to produce finely sanded surfaces ready for a high gloss finish. They are similar to the air sanders used by body shops to sand out the bodies on cars before applying a high gloss finish. If they can do this for an expensive automobile, imagine what they are capable of in the wood shop. Like all air tools, you have to keep them clean and oiled to maintain their performance, but this is easier than with the electric version. An electric sander must suck in air to cool the motor and this will often also suck in a great deal of debris over time which will eventually degrade the cooling efficiency of the motor; an air driven sander on the other hand has clean filtered air delivered to it from a remote location.
This air rushing through the motor as it spins also carries away any heat generated. Heat is the number one killer of electric tools. As the cooling airways of the motor become restricted with dust, the temperature starts to rise. When the temperature rises the bearings begin to degrade and eventually the motor overheats and fails. Air sanders are made for production work and the inner components are much more robust, most often being all metal as compared to the plastic components in the electric version. The air used to drive the tools keeps these tools cool to the touch, a fact that will be welcomed on a hot summer day. On a cool autumn afternoon, they can even feel cold when using them for an extended period of time.
As with all tools, after years of service your sander may exhibit a drop-off in power, which means the motor may need replacing. Models like those in the Dynorbital line (dynabrade.com) feature drop-in motors. These motors can easily be changed on most models in less than ten minutes with just a few tools. Often a thorough cleaning and replacing the vanes on the motor will restore the sander to like new performance. Most quality models used by professional shops will be supported with a complete line of renewal parts that can be ordered as the originals wear out.
There are several different styles of air sanders on the market, including inline (long bed or straight line), jitterbug, belt, orbital, and random orbital. Of these styles, woodworkers will be most familiar with, and likely find the greatest use for, random orbital sanders.
Air orbital sanders come in one of three different orbit options: 3⁄32”, 3⁄16” and ⅜”. For most woodworking applications, choose a model with a 3⁄32” or 3⁄16” orbit. A 3⁄16” orbit sander, like the Campbell Hausfeld PL1565 (chpower.com) is the one best suited to general sanding tasks, while a 3⁄32” orbit model, like the Samona 18778 (samona.com) is used for ultra fine sanding. There are models that offer hook and loop and PSA pads in the common five and six inch sizes. These sanders typically run at 10,000 OPM (orbits per minute), weigh in at about two and a half pounds, and require anywhere from 5 to 15 CFM of air at 90 PSI. The Campbell Hausfeld requires 11.6 CFM while the Samona consumes 6 CFM. Some sanders come with a speed adjustment on the tool, which allows for infinite control over the orbital speed, while others must be controlled via an inline regulator or by the regulator on the compressor (see “Compressors“, Apr/May ’08, Issue #53).
Another variation on this tool is the angled random orbital sander, such as the Grex AOS368 (grexusa.com). This is a small 2” angled sander with a pistol grip similar to that of a cordless drill. The small head allows it to be used in tight areas that other sanders can’t reach and can be equipped with an optional 3” head when you need to sand a slightly larger area. The Grex has a 105º angled head, runs at 15,000 OPM, weighs a mere 1.4 pounds, and consumes only 2.2 CFM. This makes it one of the few air sanders that can be operated on a portable air compressor.
These sanders typically come in one of three styles: non-vacuum, central vacuum and self-generated vacuum. The non-vacuum version of the sander has no provision for pickup of the sanding dust at the source. When using a sander of this type, use adequate local collection such as a downdraft sanding table in combination with an ambient air filter, and a respirator.
The central vacuum model is equipped with a fitting that allows it to be connected to a central dust collection system like any other sander. The self-generated vacuum model incorporates a venturi design that creates its own airflow to carry the debris into a remote collector, without the need for an external vacuum line. It is the ideal choice when you do not have a central collection system installed.
OK, so now you are probably wondering why we don’t all have these fantastic labour-saving sanding tools in our shops. The simple answer is that to operate these tools, you typically need a large air compressor. Most air sanders consume a great amount of air with many falling in the 14-18 CFM range. To run these sanders you need a compressor that can supply them with the required amount of air, which normally means running at least a 5 HP compressor with at least a 40 gallon tank. If you are purchasing a compressor, this is definitely a case where bigger is better.
For intermittent use, and where the air consumption of the air sander is under 5 CFM, such as the Grex AOS368, you can use a portable air compressor (as long as the CFM rating of the compressor is close to the air consumption requirement of the air sander). However the compressor will operate at 100% duty cycle.
Pneumatic sanders are tough production tools designed to make a less than pleasant task as painless as possible. In a professional shop that has been plumbed for air and has an adequate commercial grade compressor, these sanders offer unsurpassed user comfort because of their light weight and cool operation when used for extended periods. They are capable of aggressive swirl free cutting which will reduce the time spent sanding, letting a shop be more productive.
The casual user will need to weigh the advantages offered by the sanders against the need to invest in a much larger and expensive compressor than might normally be required.