Four years after I bought my Fein
sander, the manufacturer is still advertising
that its 636 triangular sander
"eliminates hand sanding." This is not
precisely true, but it comes awfully close.
Fact is, this machine can sand all the way
into a corner (such as a drawer bottom)
without disfiguring adjacent surfaces
(like the drawer sides). It can do this
because the sanding head oscillates
extremely rapidly (20,000 strokes per
minute) through a very narrow range of
movement (only 2°).
Unlike tools with a fundamentally
rotary action, such as random-orbit
sanders and disc grinders, the Fein's sanding
action eliminates radial momentum,
which typically drives the abrasive material
into unintended surfaces.
Instead of spinning a disc, the Fein has