Sheet Sander Versus Random Orbital Sander

When it comes to light to medium sanding, two of the most commonly used powers tools are the sheet sander and the random orbital sander. Here's how these tools stack up against each other and when to favor using one over the other.

Sheet Sander

The sheet sander, also known as a palm sander, a quarter sheet sander, pad sander, or an orbital sander, uses quarter sheets of sandpaper, held in place against a rectangular pad by spring-loaded clips. The pad vibrates in tiny circles or orbits to produce a sanding action.

The sheet sander is primarily used for light to moderate duty sanding tasks. These tasks include final smoothing of the wood surface, sanding between coats of finish, and smoothing of curved surfaces that are difficult to sand with larger, more powerful sanding tools. With a little care, sheet sanders can be used to sand joints where two pieces of wood meet at a right angle.

One of the advantages of the sheet sander is that it can fit into corners or tight areas that would be difficult or impossible to do with a random orbital sander. Also, it is easier to control a sheet sander when sanding edges, or otherwise trying to sand with a light touch.

Random Orbital Sander

A random orbital sander, also known as an orbital sander, a random orbit sander, or a dual action sander, employees a random sanding orbit that produces a near swirl free finish. The random orbit is achieved by a dual action movement: the sanding disk spins at high speeds of 20,000 to 25,000 RPM while the circular sanding pad simultaneously moves in an elliptical orbit so that no single spot on the disc travels the same path twice.

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. This tool tends to be slightly larger and heavier than a sheet sander.

Sanding Aggressiveness

A random orbital sander removes material more aggressively than a sheet sander and less so than a belt sander. It is easier to ruin a surface with an random orbit sander compared to a sheet sander. Because of its aggressiveness, a random orbital sander is not recommended for sanding between coats. Go with the sheet sander - or hand sanding - for this task.

A sheet sander is easier to control than a random orbital sander. Although it sometimes leave swirl marks behind because it's orbit is circular and not random, the effect is not that noticeable if the tool is not kept in any one spot for too long and a proper grit sequence is followed.

Cost

Sheet sanders are typically less expensive than random orbital sanders. Furthermore, they are less expensive to operate because they use standard sheets of sandpaper. With either tool, best results are achieved when a sequence of several progressively finer grits is used. For example, one might start sanding using 100 grit paper, switch to 150 grit, and then finish up with 200 grit.

Health and Safety

Sheet sanders vibrate a lot and prolonged use can result in hand fatigue and numbness. A gel-filled anti-vibration glove and frequent breaks are recommended. A random orbital sander typically causes less hand fatigue and numbness than a sheet sander. However, the machine's vibration will produce these symptoms with extended use so frequent breaks and anti-vibration gloves are also recommended.

A random orbital sander uses circular sanding disks, usually 5 to 6 inches in diameter, that attach via a pressure sensitive adhesive (PSA) or a hook-and-loop system (similar to Velcro). Holes in the sanding disks and the pad enable a random orbital sander to be hooked up to a dust collection system. This facilitates sanding efficiency and reduces sanding dust in the work environment. A sheet sander generally produces less dust than a random orbital sander but it is still a good idea to purchase a model with dust collection capabilities.