High Quality Content by WIKIPEDIA articles! Random orbit sanders, also called Dual-Action or D.A. sanders (referring to the rotation of the disk and the head) are hand-held power sanders where the action is a random orbit. They were first introduced in the early 1990s and quickly became tremendously popular. Random orbit sanders combine almost the speed and aggressiveness of a belt sander, with the ability to produce a finer finish than that available from a standard, slow speed, orbital finishing sander. The random orbit is produced by simultaneously spinning the sanding disk and moving it in an ellipse, which ensures that no single part of the abrasive material travels the same path twice. Because of this unique random sanding action, the tool does not leave swirl marks, and it is not sensitive to the direction of the wood grain.