The Differences Between a Pneumatic Random Orbital Sander and an Orbital Sander

The Basics

• A random orbital sander differs from a standard orbital sander in the way that the sanding pad moves. The motors of both sanders cause the pads to rotate (orbit) in an eccentric pattern around the central axis of the motor shaft. Random orbital sanders add spin to this eccentric rotation. This creates a more random scratch pattern as you move the tool across the work surface, giving a smoother, more-thoroughly sanded finish. The combined spinning and rotating action makes a random orbital sander an aggressive sanding tool that can often be used with finer grit paper than you would usually use for any given job.

Electric Sander

• This type of random orbital sander is available in abundance at local hardware and home stores. They all feature robust electric motors, and some are available with multiple speeds to tailor the sander to the job at hand. The heavy motors are a plus on horizontal surfaces, less so on vertical ones when holding them can become quite a chore. Almost all electric random orbital sanders come with some sort of dust containment system, from attached dust bags to provisions for attaching them to a Shop-Vac.

Pneumatic Sander

• Pneumatic random orbital sanders are very common in collision repair centers and some commercial production woodworking shops. Because they are powered by air, and thus have no heavy electric motors, they are easier to use and cause less arm fatigue on large jobs. Because they rely on the flow of air to drive them, their speed is easily adjustable. They have fewer moving parts and are usually less expensive initially.

  On the downside, they require a lot of compressed air to operate, which means you'll need a fairly large, expensive compressor to run one. If that air isn't properly filtered and the sander is poorly maintained, such tools can also spit tiny droplets of oil on the work surface. That's no big deal on a car body but a very big deal on an expensive piece of furniture.

  Although models with dust bags are available, most employ some sort of central vacuum system for dust removal, adding another hose to contend with in addition to the one supplying all that compressed air.

Considerations

• If you already have a high-volume compressor and a central vacuum system, a pneumatic random orbital sander is worth considering. This is especially true if you sand on a daily basis, which could wear out electric models and bring regular replacement costs into the equation. To solve the oil spitting problem, avoid oiling the tool altogether, although that means frequently rebuilding the sander.

  For the average woodworker, a modern electric random orbital sander will handle the most-likely jobs. They're fast, efficient and full-featured, and their popularity has driven the costs of even the highest-quality models down to a reasonable level.