A random orbit sander relies on a pad that both oscillates from
side to side and turns in a circular motion to create a virtually swirl free
sanded surface. This makes them invaluable for sanding 90 degree joints on many
wooden items such as rails and stiles and cabinet face frames.
They tend to cut
much more aggressively than other sanders and, unlike some other types, the less
pressure you put on them, the better they cut. Consequently, they are far less
tiring to use than traditional pad or belt sanders....and they do more work for
the effort expended by the operator at the same time!
Air driven Random orbit sanders require 14CFM or more air
flow to operate. Because the average home shop compressor rarely puts out more
than 4 to 10 CFM, we won't discuss them any further herein. There are two basic
shapes of Random orbit sanders, regardless of whether air or electrically
driven: Right angle (much like a grinder) and inline. There's a sub species of
inline Random orbit sanders called "palm grip" as well.
Right angle Random orbit sanders are harder to control and tend to "dig
into" the stock with the edge of the disk until the operator learns to
balance the spinning pad out in front of his hand. For this reason, the inline type
dominates sales in the tool stores
Because 5" disks are much easier to find and cheaper
than the 6" disks, more than 70% of all Random orbit sanders sold are the
5" variety. Some come with PSA
(pressure sensitive adhesive) pads and others come with H&L (hook and
loop). Hook and loop (Velcro) disks are sold in boxes of 5, 25 and 50. Both
5" & 6" come in grits as large as 60 and as fine as 320 in a
variety of paperweights.
The jury is still out on which saves the mostmoney overall as H&L disks can be changed at will and reused when switching to finer grits to finish off a project and PSA disks are, for all intents and
purposes, for one time use only, once removed, they seldom stick tight again the 2nd time...except to each other.
Almost all Random orbit sanders spin between 8,000 and
12,000 RPM. Most of the single speed models run at 10,000 RPM only. Many are
variable speed with the operator controlling the orbits/RPM by two methods that
work well in conjunction with each other: a knurled switch that adjusts and how
much pressure the operator puts on the trigger switch. We find variable speed
preferable to fixed speed, especially for touch up work on sanding sealer or
Palm grip Random orbit sanders are generally designed for
finish work, sanding sealer and the like. The ones with handles are preferred
for rough work and final sanding.
All Random orbit sanders generate a lot of dust...more than
just about any other hand held power tool. Those who are dust phobic areadvised that
they will also need an adapter to fit these hoses into the 2 1/4"
of a standard shop vacuum cleaner.
Random orbit sanders should be brought up to full speed
(whatever you've got it set at if it is variable speed) before coming into
contact with the work surface. Likewise, it should be completely lifted off the
work surface before it is shut off or even slowed down. Failure to do so may,
and probably will, result in swirl marks in the work piece at the last point of
Most, if not all, ROS makers offer three different type pads
for their machines: soft, medium and hard backed. All come standard with a
medium pad. Hard pads are wonderful for use on wide flat surfaces. Medium pads
will follow a shallow contour. Soft pads will follow any shape, within reason,
and are excellent for things like cleaning up the profile on a raised door
panel. For reasons known but to God, soft pads DO have a tendency to toss off
H&L disks once in a while but the others don't.
Random orbit sanders don’t use much current to do their
work. They range from a low of 1.8 amps to 7 amps all well under 1 HP.
Random orbit sanders have been around since the 1940's in
the automobile and other metal finishing industry as air driven models. It was
only when they were converted to electrically run tools twenty years ago, that
they gained dominance, as the finishing sander of choice with woodworkers.
While they won't replace a belt sander for heavy duty rough surface smoothing
or a 1/3 to 1/4 sheet pad sander for getting into tight corners, overall, they
will end up doing 90% of your sanding for you...with much better results and
far less effort.
Corner Detail Sanders
Corner detail sanders have been on the market for years.
They were invented by the Fein Corporation, who owned the market on the gizmo's
at around $500.00 until Ryobi, came out with their single speed model for
Like Random orbit sanders, they sand by using a somewhat
orbital motion, although a couple may be "in line" (straight back and
forth) as we never actually checked since our eyes won't see a thing moving
1/32" or less at 8,000+ RPMs.
A Corner detail sanders will fit almost anywhere you can
stick your arm, with refined corners to give the user additional small,
straight edges to sand to opposing parts, as inside of face frames.