Random Orbital Sander
What:
A random orbital sander is a hand-held power sander that produces a near swirl free finish due to a random sanding orbit. The random orbit is achieved by simultaneously spinning the sanding disk at high speeds up to 25,000 RPM and moving it in an elliptical orbit such that no single abrasive particle travels the same path twice. Since their introduction in the early 1990s, random orbital sanders have become very popular among woodworkers thanks to their ability to sand aggressively while producing far fewer swirl marks than other power sanders, such as belt sanders. A random orbital sander is also known as an orbital sander, a random orbit sander, or a dual action sander.
Random orbital sanders use round sandpaper discs that attach via a pressure sensitive adhesive or a hook-and-loop system. The discs are typically 5 inches in diameter and come in a number of different grits, from 60 (coarse) to 220 (very fine). It is important to buy the proper type of sanding disk for a particular model of sander. Most decent quality orbital sanders are equipped with a dust collection port, which allows an external vacuum to suck sanding dust through the holes in the paper and sanding pad and away from the work surface. Another desirable feature is a sealed switch to keep sanding dust from clogging up the switch mechanism, which could make it difficult to turn the unit on or off.
Why:
The random orbital sander has become the go-to sanding tool in many woodshops in recent years. In terms of sanding efficiency, it sands much more aggressively than a conventional sheet sander and depending on the grit used, nearly matches the aggressiveness of a belt sander. Because of its random sanding action, it produces a smooth surface without the swirl marks left by these other power sanders. This means that is not sensitive to direction of the wood grain, a feature that is very beneficial when sanding two pieces of wood that join at a right angle. Another big advantage of the random orbital sander is that the dust collection holes in the sanding pad and disks allow sanding dust to be removed before it can accumulate, improving the sanding action and providing a near dust free working environment.
Notes:
When purchasing a random orbital sander, consider the type of sanding disc that it requires. Some models use a pressure-sensitive adhesive (PSA) peel-and-stick disc while others use hook-and-loop discs that have a Velcro like backing. Many woodworkers prefer hook-and-loop disks because they are easier and faster to change, an important feature when going through a grit sequence. Plus they can be reused. On the other hand, PSA discs are less expensive and the attachment pad tends to be harder and longer lasting than the pad on a hook-and-loop unit.
A random orbit sander should be turned on when the sanding disc is in contact with the wood surface. If the unit is turned on before being lowered to the surface, the disc spins very rapidly, making it difficult to control the machine once it is lowered onto the surface.