Unraveling
the mystery of the grades is easy. In the list above, the
larger particle sized grades begin on the left and each
successive grade is smaller. Particles are sized using U.S.
Standard Sieves/Screens.
Examples:
+8
Grade: The majority of particles are retained on a #8
sieve.
-40
Grade: The majority of particles pass through a #40
sieve.
1420
Grade: The majority of particles pass through a #14
screen and are retained on a #20 screen.
Particle
Sizes
Following
is a table which shows the U.S. Standard Sieve number, the
opening size in microns and the corresponding opening size
in inches.
Particle
Sizes According to Various Sieve Standards
US
Standard
Inches
Microns
5/16"
.312
8000
4
.187
4750
6
.132
3350
8
.0937
2360
10
.0787
2000
12
.0661
1700
14
.0555
1400
16
.0469
1180
18
.0394
1000
20
.0331
850
30
.0234
600
40
.0165
425
50
.0117
300
60
.0098
250
80
.0070
180
100
.0059
150
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