Belt Sander Versus Random Orbital Sander

There are many different power tools for smoothing a rough surface but two of the most commonly used ones are the belt sander and the random orbital sander. Here is a comparison of these labor saving tools including how each works, sanding aggressiveness and when to use one over the other.

Belt Sander

A belt sander is designed to rapidly remove wood or other materials. It is not a finesse machine. It uses abrasive coated belts that revolve around two metal rollers with a flat metal plate called a platen in between. The backs of the belt rides against the platen which projects out slightly more than the rollers.

A belt sander is typically the first power tool to use in smoothing a rough surface such as a rough milled piece of lumber, or a weather-beaten deck board. After the initial sanding is performed with the belt sander, other tools such as sheet sanders and orbital sanders can be used to finish the job.

Belt sanders also work well at other tasks such as removing an old finish from a wooden floor, flattening a glued up panel, and rounding the corners of a board or piece of furniture

Random Orbital Sander

The random orbital sander, also known as an orbital sander, a random orbit sander, or a dual action sander produces a near swirl free finish by spinning a sanding disk at high speeds up to 25,000 RPM and simultaneously moving it in an elliptical orbit such that no single abrasive particle travels the same path twice.

The random orbital sander does not remove material as aggressively as a belt sander but leaves behind far fewer swirl marks or scratches in the surface. A big advantage of the random orbital sander over a belt sander is the ability to sand two pieces of wood that joint at a right angle without leaving cross-grain swirl marks.

The random orbital sander is typically used after the primary surface smoothing has been completed with the belt sander. It has the mop up role of removing the sanding marks left behind by the belt sander, followed by final smoothing using progressively finer sanding grits.

Sanding Belts Versus Discs

A handheld belt sander generally uses belts that are 3 to 4 inches wide and 18 to 24 inches in length. Some of the smaller belt sanders use belts that are 2-1/2 inches wide by 14 to 16 inches in length. Many belts are made from aluminum oxide in grits ranging from 40 (very coarse) to 220 (very fine). Sanding belts cost considerably more than the sanding discs used on a random orbital sander but they are also thicker and will last much longer.

The random orbital sander uses round sandpaper discs that attach via a pressure sensitive adhesive or a hook-and-loop system. The discs are usually 5 to 6 inches in diameter and come in a number of different grits, from 60 (coarse) to 220 (very fine). Dust collection holes cut into the discs allow for the vacuum removal of sanding dust, improving both the sanding action and air quality of the work environment. Although sanding disks are less expensive than sanding belts, they require more frequent replacement. It can sometimes be difficult to find sanding disks, especially for off brand models.

Belt Sander Caution

A belt sander is much more powerful and aggressive than a random orbital sander. Although this allows for more rapid material removal, the downside is that the belt sander is more difficult to control and can quickly ruin a piece if one is not careful. A belt sander is also more dangerous than a random orbital sander specially if a very coarse sanding belt is in place.

A belt sander will leave behind sanding marks in wood so it helps to sand with the grain as much as possible to minimize the amount of cleanup sanding required afterwards. It takes a lot more effort to remove deep sanding scratches with a random orbital sander.