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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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Four Corners International, Inc.

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Copyright 2005-2006 by M. Bradley Walker.  All rights reserved.

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