Electric sanders can be used on an array of materials from wood to glass to metal, nearly any surface where you wish to remove a coating layer or you desire to smooth out. The most familiar application is to wood, especially stripping old paint and preparing the surface for varnishing or painting. Thisoldhouse.com also notes that electric sanders can be used to clean surfaces between finish coats.
A palm sander is defined primarily by size, as the term refers to the fact that palm sanders are intended to be used in one hand, as opposed to more powerful two-handed sanders. According to Stason.org, the palm sander is useful for giving a good finish and working with fine-grit sandpaper. Because of the lower engine power, the palm sander is gentler and can do finer work than more powerful alternatives. However, a palm sander is insufficient for cleaning up large areas.
Random Orbital Sanders
Random orbital sanders are defined by the unique motion of the sandpaper. The disk in a random orbital sander is round and spins in a circle during operation while the whole pad moves in an oval pattern. According to Thisoldhouse.com, none of the abrasive particles will follow the same path twice, which leads to an absence of the swirl patterns that sometimes occur when sanding against the grain. A random orbital sander can cover a lot of ground quickly, but they are not as powerful at removing a lot of material as belt sanders.
An example of a palm sander is the Makita BO4556. This model is held on top, with the palm facing down and has the on/off switch set close to the grip for easy one-handed operation. This leaves the other hand free to hold the material that is being worked on, making the palm sander ideal for smaller projects. The engine draws 2 amps and creates 14,000 oscillations per minute. According to Makita.com, the unit weighs 2.4 lbs. An example of a random orbital sander is the Makita BO5030. This model has an engine that draws 3 amps and creates 12,000 oscillations per minute. The unit weighs 3.3 lbs. and has a 5-inch abrasive disk.
Although palm sanders and random orbital sanders are not entirely distinct-- because there are palm-sized random orbital sanders--the primary distinction between these two types of sanders is that palm sanders are small and fitted to finish work, while most random orbital sanders are larger and more powerful, suited for working on larger surfaces. Palm sanders can more easily work around edges, while random orbital sanders are a better fit for flat surfaces.