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Grit
No, a "grit" is not the singular form of a breakfast food from
the Southern United States, it's a term used to refer to the size of
the abrasive particles used in sandpaper, abrasive belts, diamond
hand pads, or similar tools.
Grit is sized by number, with the smaller numbers used for
larger, coarser particles, and larger numbers used for smaller,
finer particles. The numbers refer to the number of openings
in a square inch of mesh screen which is used to sort the loose
abrasive. For example, 200 grit abrasive refers to particles
that fell through a screen with 200 holes per square inch.
Common grit sizes used in glass working are 60 and 100 (for rough
grinding), 220 (medium), and 400 (for fine smoothing). Sizes
above 400 are generally used for metals, but not for glass work.
When working with grit, the standard process is to start rough
grinding with a coarse grit (such as 60 or 100). This removes
glass quickly. By switching to finer and finer grits (220, then 400,
for example), the glass can continue to be smoothed and prepared for
polishing if desired.
Grit particles can be made of various substances, but the most
common in glass working are diamond, silicon carbide, and aluminum
oxide. As you would expect, diamond is the most expensive of
these, but it does last much longer. Silicon carbide is more
commonly used for rough grinding and smoothing, while aluminum oxide
is more commonly used for very fine particle sizes and as a sand
blasting abrasive.
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Copyright 2005 Brad Walker.
All rights reserved.
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