sieves

Sieves are a very ancient tool, at least as old as the open weave baskets used to separate grain from refuse, the earliest example of a go/no-go gage. A later more sophisticated sieve was the medieval miller's bolting cloth. Even more precise sieves began to be made during the Industrial Revolution. In 1800, for example, to extend the supply of grain during an agricultural crisis the king of England forbade the baking of bread with flour that would pass through a sieve with 13 wires on each side of a square inch. (41 George III c 16 1800)

Many occupations are concerned with the size of large numbers of small objects, such as grain, seeds or soil particles. If a graded series of sieves is available, a batch can be shaken through a stack of sieves with increasingly smaller holes. Weighing the amount left behind in each sieve gives a series of masses which is a size distribution for the particles in the batch. In such situations it is more accurate to describe the sizes of the particles in sieve numbers, rather than as particle diameters. For an example of how sieve numbers are used to grade a commercial product, see abrasives.

The sieves used in industry and the laboratory are precision products. The smaller the particle that is not to pass through the sieve, the finer the wires of the sieve–but despite that, the smaller the proportion of the sieve's area which is hole.

Test sieve apertures in millimeters or micrometers as recommended by the ISO. (See note 1, below.)	U.S. Alternate sieve designations, a survival of an older system. Mesh sizes are roughly the number of openings per inch.	Tyler Screen Scale Equivalent Designation
25.00 mm	1 inch	—
19.00 mm	3/4 inch	0.742″
16.00 mm	5/8 inch	0.624"
14.00 mm
13.20 mm
12.50 mm	½ inch	—
11.20 mm
10.00 mm
9.50 mm	3/8 inch	0.371"
9.00 mm
8.00 mm	5/16 inch	2½ mesh
7.10 mm
6.70 mm
6.30 mm	¼ inch	—
Fine Sieves
5.6 mm	3½ mesh	3½ mesh
5.00
4.75	4	4
4.50
4.00	5	5
3.55
3.35	6	6
3.15
2.80	7	7
2.50
2.36	8	8
2.24
2.00	10	9
1.80
1.70	12	10
1.60
1.40	14	12
1.25
1.18	16	14
1.12
1.00 mm	18	16
900 µm
850	20	20
800
710	25	24
630
600	30	28
560
500	35	32
450
425	40	35
400
355	45	42
315
300	50	48
280
250	60	60
224
212	70	65
200
180	80	80
160
150	100	100
140
125	120	115
112
106	140	150
100
90	170	170
80
75	200	200
71
63	230	250
56
53	270	270
50
45	325	325
40
38	400	400
36		—
32	450	—
28		—
25	500	500
22		—
20	635	625
15		800
10		1250
5		2500

(1) The ratio between adjacent sizes is the fourth root of 2, so the aperture size doubles every 5th size. Red lettering identifies sizes in common use in the United States that are ASTM supplementary values.