Advances in random orbital sanders over the past few years have made them the first sander you should consider when outfitting your shop with power tools. Random orbital sanders can be set up to sand very quickly or very smoothly, with the added advantage that the random action will leave very few sanding marks on the face of the wood (as opposed to sheet sanders, which do not have a random action and can leave swirl-shaped marks on the wood, or belt sanders, which are more commonly used for removing a lot of material at one time).
The feature that makes these sanders so unique is its ability to sand in a completely random orbit, at speeds of up to 25,000 RPM. This completely random motion is what allows the sander to be able to leave a smooth finish without the sanding marks that palm sanders or belt sanders leave behind.
Most random orbit sanders use sanding disks, typically in a 5-inch diameter affixed to the foam-rubber pad by hook & loop connections. These disks usually have eight holes in a circular pattern that line up with the dust collection holes in the pad. Sanding disks typically are available in a number of grits, from as low as 60 (coarse) to 220 (very fine).
When buying a random orbit sander, there are a few features you should definitely have. First of all, dust collection is a must. Not only should the sander have a dust collection bag or filter that accompanies the unit, but it should be able to be connected to a dust collection or portable vacuum unit. This will make sanding much cleaner, and keep a lot of the dust that sanding creates to a minimum.
Also, the unit should have a sealed switch, to keep dust from getting into the switch which might cause the unit to be difficult to turn on or off.
The sander should be well balanced and feel comfortable in your hand. If possible, turn the sander on and feel the vibrations. All sanders vibrate, but an excessively vibrating sander will cause considerable fatigue when working on large sanding projects.
Additional Features to Consider:
Some higher-end random orbital sanders have variable speed controls. This is very useful when sanding some heat-sensitive materials where you might want to keep the heat lower. However, in woodworking applications, this has little practical use. Additionally, the orbital sander you choose should have a trigger lock, to lock the power on when in use.
Tips for Using a Random Orbital Sander:
When working with a random orbital sander, keep the sander moving with the grain of the material. Leaving the sander in one place may cause an uneven finish. Also, take care to avoid rounding over the edges. If an eased edge is desired, use the sander to create a consistent but distinct small chamfer on the edge rather than rounding over the action from the face.
The Last Word:
Be certain that whichever random orbital sander you choose, your home center or building supplier carries sanding disks made to fit that particular model. The last thing you want to do is buy a sander that you love, only to find that sanding disks are nowhere to be found or only available in a limited variety of grits.