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November 2003 - Cutting Edge |
| A
bounty of abrasives gives woodworkers good reason to go with
the grain |
|
Sanding
is often the most time-consuming part of a project, and choosing
the perfect grit can be daunting for the uninitiated. Whether
you’re looking for sanding belts and discs engineered
to withstand the rigours of rapid stock removal without clogging
or a flexible sanding block to follow irregular contours, the
harder and sharper the mineral, the deeper the scratches. Softer
minerals with the same grit size will cut slower but leave a
smoother finish. And the secret to getting good results with
less tedium is taking full advantage of today’s improved
papers, and choosing the right one for the job.
[1] Glit’s Finishfast synthetic
steel wool pads are reusable and won’t rust. Use between
final coats of stain and in stripping old paint. $2
[2] Glit’s drywall sanding screen
is made of reusable silicone carbide grit. It features an open-mesh
sanding surface for less loading and is recommended for sanding
drywall joists, plaster and spackling. Can also be used on wood,
metal and painted surfaces. $5
[3] Klingspor’s 4 1/2"
circular sanding disc is aluminum oxide grit with a
no-load, zinc stearate coating for longer wear. A loop backing
attaches to an orbital sander plate with a hook facing. Use
with dustless sanders, such as Ryobi or Sears sanders, that
have 4.5" eight-hole plates. $1
[4] Glit’s peel-and-stick adhesive
paper discs are coated with aluminum oxide that’s bonded
to an adhesive backing, and come in packages of five in assorted
grit sizes. $3
[5] Stockroom Supply’s sanding
mop, made of gold-coloured, aluminum- oxide grit, is designed
for metal or woodworking applications. The Klingspor grit is
stearate-coated or non-loading, so it won’t plug or heat
up and is glued to a flexible, pre-slit cloth backing. Great
for wood moulding, carvings and restoring antiques. $40
[6] Glit’s 4" strip-away
disc is a rust and paint stripper that comes with an arbor for
use with an electric drill. Ideally used for blending, deburring,
and finishing metal and fibreglass. $10
[7] 3M’s Sandblaster sanding
pad is buildup-resistant and ideal for contoured surfaces of
bare wood or drywall. Wet and dry applications. $4
[8] Lee Valley’s replacement
sleeves for drum sanders are cloth-backed with aluminum oxide
grit. Use with flex shafts, drill presses or any chucked tool
that takes a 1/4" shaft. $7 for 10 assorted sleeves
[9, 10 and 11] 3M Sandblaster Sandpaper
is colour-coated for easy
identification among grits. Green (P60-grit) is for heavy and
moderate stripping, purple (P100-grit) is for bare-surface smoothing,
and yellow (P180-grit) is for between coats and finishing. $5
for a package of 3
[12] Glit’s all-purpose sanding
block is an aluminum oxide-coated sponge for wet or dry sanding.
Each sponge has four abrasive sides. $2
[13] GatorGrit’s 3" sanding
belt for belt sanders is semi-open-coat aluminum oxide, with
an X-weight cloth backing. $2
[14] Glit’s 5" Sanding
and Finishing Kit consists of three assorted fibre discs, a
1 1/4" arbor and a backing pad for use on electric drills.
Aluminum oxide discs are resin-bonded to a fibre backing. $12
[15] Rhodes American steel wool is
available in eight abrasive grades ranging from super fine (finishing
grade) to extra coarse. Uses include polishing furniture and
heavy-duty stripping. $4 |
| ABRASIVE
ACTION |
ALUMINUM OXIDE
(Man-made) |
Properties: Not as sharp as silicon carbide,
but lasts longer. Hard grained. High degree of friability
(i.e., it fragments under heat and pressure, creating
new sharp edges) Application: A good all-rounder.
Works well for power sanding wood or metal. Finer grits
can be used in sharpening applications and for finishing
metals, wood and other high-tensile- strength materials
without excessive fracturing or shedding |
ALUMINA ZIRKONIA
(Man-made) |
Properties: An alloy of aluminum
oxide and zirconium oxide. Zirconium is a very dense,
friable material, which gives this sandpaper long life
on heavy stock-removal operations. Sharp, hard and durable.
Cuts faster and lasts longer than aluminum oxide, but
not as long as ceramic. Application: Used mostly
on belts and discs for machine sanding. Works well on
stainless steel, titanium and other hard steels. Can also
be used on wood |
CERAMIC
(Man-made) |
Properties: More durable and expensive than other
abrasives. Often bonded with aluminum oxide. Application:
Used primarily on belts and discs for power sanding.
Generally available in lower grits for shaping and levelling
wood |
EMERY
(Natural) |
Properties: Very soft. Usually
comes on flexible cloth backing. (Cloth backings are the
stiffest and produce the coarsest and fastest cut) Application:
Excellent for sanding and polishing metal. Good for rust
removal, polishing, deburring, and corrosion and paint
removal |
GARNET
(Natural) |
Properties: Garnet is soft and dulls quickly
compared to man-made abrasives, but cuts smoother than
other abrasives Application: Suitable for sanding
bare wood. Excellent for final sanding before applying
a finish |
SILICON CARBIDE
(Man-made) |
Properties: Extremely hard
and sharp, but wears quickly Application: Suitable
for cutting harder materials, such as paint, fibreglass
and plastic. Best for smoothing joint compound and removing
dust nibs between coats of finish. Extra-fine grits can
be used for sanding the final finish coat |
| FINER POINTS |
 Apart
from the manufacturer’s name, grit size (the number
of teeth per square inch) is about the only information
consistently found on the back of sandpaper sheets. There
are three commonly used abrasive grading systems in Canada.
The Coated Abrasives Manufacturer’s Institute (CAMI)
regulates the U.S. standard scale. These products simply
have numbers, such as 80, 120 or 320, printed on them.
The Federation of European Producers Association (FEPA),
or European scale, uses the letter “P” in
front of the grit size (as in P1000). Some manufacturers
offer the micron grade scale, which has the Greek letter
µ (micron symbol) after the number (as in 320µ)
and are best suited for jobs in which a highly polished
surface is desired, such as working with metal and in
sharpening applications. Factors such as the type of backing
material, the weight, the type of abrasive material and
whether the sandpaper is stearated, open or closed coat,
do contribute to the sandpaper’s performance but
may not be indicated on sandpaper sheets.
|
| CLOG STOPPER |
 The
spaces between grit particles are like the gullets of
a saw blade: the grit can’t remove wood when the
spaces are full. However, if you use a power sander, you
can get extra life out of your discs and belts. When your
sandpaper is loaded, simply offer a block of crepe rubber,
such as the Veritas sanding block (Lee Valley Tools, $9),
to the rotating belt or disc and apply light, firm pressure.
Discs will become considerably cleaner after a few moments
as the block strips out accumulated dust and fibre. |
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