The random orbital sander is an essential part of most woodwork- ing facilities. The tool allows rapid removal of material to create a flat surface that is ready to accept stain or coatings. Along with their many advantages, there are some issues, including swirls and excessive polishing.
Orbital sanders use two types
of movements simultaneously to
product a random scratch pattern.
The pad must spin and orbit to
create the proper scratch pattern.
This is where the backup pad
An essential part of most woodworking shops, the
comes into play. The backup pad
is the part of the sander that the
sandpaper attaches to via hook
and loop (H&L) or pressure
sensitive adhesive (PSA).
For flat surfaces, this pad must
remain flat and in good condi-
tion. When the operator tips up
the sander to dig out defects on
a surface, not only does this dig a
divot in the workpiece, but it also
damages the outside diameter
of the backup pad. Over time,
the pad starts to retain the curve
induced when the sander is tipped
up and it no longer maintains
full contact on flat surfaces. The
reduced surface area makes flat
surface sanding take much longer
and it induces many more swirls
into the surface. It is also much
easier to miss spots, leaving streaks
of inconsistent surface finish.
An out-of-balance or out-
of-square backup pad can also
produce defects. If you sand a
flat surface and feel the sander
pulling back and forth across the
surface, the backup pad needs
to be replaced. Or if the sander
bounces as the pad rotates, then
you likely need a new backup pad.
PSA disks are often harder to
remove from worn out pads, as
shown by the amount of adhesive
that remains stuck to it. The H&L
disks will fly off of the backup pad
when worn out. An out-of-balance
pad will put undue stress on the
The often overlooked
tool allows rapid removal of material to accept
stain or coatings. Here are some things you need
to know about this woodworking workhorse.
By Adam West
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