Three Different Grit “Standards”
In building fine furniture more than 50%
of one’s time goes into sanding, final as-
sembly, buffing and polishing. The sand-
ing part alone can take more than twice
the amount of time that it
took to machine all the
component parts of
the piece. Yet,
sanding processes,
tools and materials
are seldom as
carefully chosen as
are the machines
that cut the wood
components in the
first place.
Sanding, after all,
is just using some
kind of hard mate-
rial to abrade the
surface fibers of
the wood, shearing
them off to leave a
smooth feel to the
surface. Simple to
say, but hard to do
well. As you
abrade the surface
you also scratch
the surface. If
those scratch
marks are large
enough, they will
detract from, not add to the appearance
of the final product.
So, the trick is to learn how to use smaller
and smaller particles of the hard material
to remove the larger scratches and leave
smaller and smaller scratches until they
no longer are visible and to do so in such
a way that the entire surface of the fin-
ished piece is uniformly treated, corners
and all.
Initially, this work was done laboriously by
hand by scooping up naturally occurring
small rock particles (sand) and rubbing
them over the surface with animal skins
or cloth. Later, means were found
to adhere the sand to a paper
or cloth backing and what
we today call “sandpaper”
was born. That is where it
started, but far from where
it ended.
What we call “sandpaper”
today rarely is either really
sand in the way we nor-
mally think of sand nor is it
necessarily paper. The
abrasive particles can be
anything from natural ma-
terials like garnet and
diamonds that have been
carefully processed to be
as even in particle size as
possible to manmade ma-
terials like aluminum oxide
or silicone carbide engi-
neered with a very high
uniformity in particle size.
The backing material can
be various kinds of paper
derivatives or various
kinds of cloth materials or
manmade screens or
combinations of all three.
There may also be other materials added
to the abrasive surface like soaps and
waxes (called “stearates”) to help prevent
loading of the paper with small particles
of wood fibers and the resins that natu-
rally occur in the wood.
GRIT COMPARISION CHART
MICRON US CAMI
FEPA 'P'
(Festool)
JAPAN JIS
500 36 36 36
430 40
410 40
350 50 40
320 50
300 50
270 60
260 60
250 60
210 70
197 80
192 80
177 80
156 100
149 90
140 100
127 120 100
116 120
97 150 120
93 150
78 180 180 150
66 220 220 180
60 240 240
52 240 280 280
46 320 320
42 280
40 360 360
35 320 400 400
30 500
28 360 500
25 600 600
21 400 800 700
18 500 1000 800
15 600 1200 1000
13 800 1500 1200
10 1000 2000 1500
8 1200 2500 2000
7 2500
6 3000
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