Hand
Sanding Tips
12th in a series by Barb Siddiqui
There are
any number of power tools for sanding jobs: hand-held belt sanders, wide-belt
sanding machines, oscillating drum sanders and stationary disc sanders.
The most common is the palm-grip random orbit sander, a real convenience
for a small workshop. The best advice for using this tool is don't apply
unneeded pressure to the job. Instead, allow the eccentric rotation of
the pad to do the work, and apply light, even pressure all across the
surface to be sanded.
Hand sanding
before finishing a project is probably the least-liked chore in woodworking,
but doing this job poorly is a sure way to ruin what may have taken days
or weeks to build. A couple of basic rules to remember are: it is best
to sand with the grain, not across it, and also to think of sanding in
at least three steps of grits, not two. Since each individual grade of
sandpaper is meant to eliminate the scratches of the coarser grit used
before it, skipping from coarse to fine grits, without an intermediate
sanding, will most likely leave unsightly scratches under your final top
coat. So, no matter what grit size you decide to start with, plan on advancing
through by three grits, coarse to fine.
There is
a bewildering variety of sandpaper products available. Aluminum oxide
is the most economical, and is good for raw wood. Open coat sandpapers
mean there are open spaces between the grit particles, which help prevent
the sandpaper from clogging with dust and losing its effectiveness. Open
coat papers are a necessity on softwoods and on any wood that may have
a resin build-up.
Closed coat
papers have fewer spaces between the grit particles. They cut faster and
smoother, but may clog up quickly with sanding dust. These papers are
best used for final light sanding of non-resinous woods, and for use between
coats of applied finish. "Wet/dry" sandpapers, usually silicon/carbide,
are made to work with a lubricant such as water or kerosene, and are excellent
for use with finishes, or on metal.
It's best
to buy a variety of sandpapers and experiment with them for the work you
do. Store them flat and protect them from moisture. While you're at the
hardware store, purchase a "tack cloth" to wipe sawdust off
your project between sanding grits.
Sanding blocks can be anything, from a short piece of 2x4 lined with cork
to an ergonomically-designed walnut block with spring-loaded attachments
for the sandpaper. When you've decided on the size block you will commonly
use, it is helpful to measure its width, then attach an old hacksaw blade
to a piece of plywood, exactly that width from the edge of the wood. Set
a slim washer under each end of the blade to elevate it slightly, and
screw it down through the end holes of the blade. This way you have a
cutter already sized to quickly make strips for your sanding block out
of a full-sized sheet of paper.
Before you
sand, glue joints should be carefully scraped. It is best to sand and
finish any parts you can before assembly, being careful to not get any
finish on areas to be glued. Doing so will affect the glue bond, which
needs bare wood.
Sanding
irregular surfaces can be downright vexing. Curved moldings, inset corners,
thin spindles and deep grooves all present special needs when preparing
a piece for finishing. Many of these are cases that go by the old rule:
"whatever works."
Wrapping
sandpaper around a dowel works for many concave spaces. If you take time
to cut and glue different grits to 1/2", 3/4" or 1" dowels,
you'll be surprised how often you reach for them. A piece of 1/4"
square trim molding, wrapped and glued with sandpaper, works well to take
off those whiskers and rough surfaces in dadoes or grooves, and along
the edges of a rabbet cut. A piece of quarter-round molding, covered in
the same way with sandpaper, will give you a half-round and two sharp
edges for sanding in V-groove spaces. Common fingernail files are sandpaper
and can be very handy for getting into tight spaces.
For complicated
pattern moldings, a piece of packing Styrofoam can be shaped with scrapers
to match the profile needed, then covered with sandpaper to smooth the
finished product. For very small piecework, glue different grits of paper
on each side of a 3"x 7" piece of 1/4" ply and move the
workpiece over the paper, rather than the paper over the piece. This board
is also useful for chamfering the ends of dowels.
One useful
aid is made by tracing the outline of a large C-clamp onto plywood, cutting
it out and tacking a 1" strip of sanding belt to each end with a
little flex left in it. This gives you a bow-shaped handle to allow the
belt to round over edges of different dimensions, or take off a corner
when you need to.
For sanding
square edges, cut a wood block about 4"x7", then glue a 2"
x 7" piece of one grit of sandpaper on half of it, 2"x7",
and another 2" x 7" piece of finer grit of sand paper on the
other half. Glue and screw an upright divider about 3" high in the
center, being careful to set it accurately perpendicular to the sandpaper
base. The upright will serve as a 90-degree fence to hold against the
workpiece, allowing you to sand an edge square to its face, and gives
you a choice of two grits to use, depending on what needs to be done with
the edge.
Spindles
in an assembled workpiece can be sanded using a long 1" strip, simply
pulling the ends back and forth around them like a shoeshine cloth. Any
piece of sandpaper, whether you use it alone or secured to a block, will
benefit by lining its edges with common masking tape on the back side
to make it more tear-resistant.
Sandpaper
can also be cleaned, so don't be too quick to discard it. If it loads
up with dust, use a stiff brush to clear it, or get a 'File Card' with
short metal bristles to clean it off. Aluminum oxide papers have particles
that will fracture as it is used, creating new, sharp edges. If cleaned
up, it can then be used as a finer grit of sandpaper.
After sanding
your workpiece through several grits, take a moment to pass your fingers
over the work. It's amazing how much you can detect with your fingertips.
It also helps to hold a strong worklight down low at the edge of a workpiece,
then bend down and sight across the surface of the wood. Light and shadow
will show up any indentations or irregularities in short order.
Taking your
time at this stage of a project often means the difference between turning
out a piece of woodworking that looks amateurish or one that looks quite
professional. It's my goal to strive to do the very best I am able. And
then the next time, to do it even better!
Click
on the links below to see the previous articles by Barb Siddiqui.
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