What is an Orbital Sander?
Orbital sanders are for fine finishing work only and should not be used for removing any appreciable quantity of material. The flat cushioned pad over which abrasive paper is stretched rotates in small circles of about 10 mm (3/8 in) diameter The tiny circular marks it leaves can only be detected under very close examination, but to this extent orbital sanders do not come up to careful hand sanding standards. They are, however, extremely useful for rubbing down and keying paintwork in preparation for extra coats.
Usually the weight of the tool on its own provides sufficient downward pressure, though it must be steadied by hand to prevent it skating about on the surface.