Grind gage

A grind gage is an instrument which indicates the fineness of grind or the presence of coarse particles and agglomeration in a dispersion.^[1] This is important because many types of solid materials must be ground or into finer particles in order to be dispersed in liquids.^[2] The resulting properties of the dispersion vary based on the size of individual particles and the degree which they are dispersed to.

Application

Grind gages are used in a variety of fields, including; food, pharmaceutical, pigment, plastic, paint, and many others. In all of these fields, grind gages are utilized to produce, store, and apply dispersion products.

Appearance

A grind gage is typically a flat steel block which has two grooves in it with flat bottoms at each end of the gage, one end at a maximum and the other at a minimum. In between these extremes is a gradually increasing groove depth, this groove depth is determined by either one or many scales which are used to measure and determine particle size.

The majority of gages have only one scale which is measured in either mils or micrometers. 1 mil = 25.4 µm 1 mil = 0.001 inch 1 µm = 0.001 mm or 10⁻⁶ m

The National Standard scale, also called the Hegman scale may also be used. On the gage, this scale is abbreviated "NS". With this scale, groove depth is measured on a scale of 0-8, and as the numbers go up, the particle size decreases. 0 Hegman = 4 mil/100 µm particle size 4 Hegman = 2 mil/50 µm particle size 8 Hegman = 0 mil/0 µm particle size

Usage

The grind gage is used by placing an excess of the material in the deeper groove at the maximum, and, using a scraper, drawing the material in the direction of the minimum. The point where oversized particles start to appear in high density determines the rating for that material.^[3]

References

• Koleske, Paint and Coating Testing Manual, p. 743, ISBN 0-8031-2060-5