The term Mesh is used to describe the size of an abrasive particle. In some instances, such as withAluminum Oxide GritorSilicon Carbide Grit, a single number is used. This does not mean every particle in that product is exactly that size but rather than mesh size indicator is approximately the mean or average size of the range of particles in that grade. In other instances, such as withWalnut Shell GritorGlass Beads, two numbers are used. This indicates that all of the particles in that grade of product are within that range of mesh sizes.
U.S. Mesh Size (or U.S. Sieve Size) is defined as the number of openings in one square inch of a screen. For example, a 36 mesh screen will have 36 openings while a 150 mesh screen will have 150 openings. Since the size of screen (one square inch) is constant, the higher the mesh number the smaller the screen opening and the smaller the particle that will pass through. Generally US Mesh is measured using screens down to a 325 mesh (325 openings in one square inch).
Sometimes the mesh size of a product in noted with either a minus (-) or plus (+) sign. These signs indicate that the particles are either all smaller than (-) or all larger than (+) the mesh size. For example, a product identified as -100 mesh would contain only particles that passed through a 100 mesh screen. A +100 grade would contain particles that did not pass through a 100 mesh screen. When a grade of product is noted with a dash or a slash is indicates that the product has particle contained within the two mesh sizes. For example, a 30/70 or 30-70 grade would only have particles that are smaller than 30 mesh and larger than 70 mesh.
The terms Mesh and Grit are often confused. The terms can be used interchangeably when referring to abrasive grit. A 60 mesh Aluminum Oxide can also correctly be termed a 60 grit Aluminum Oxide. In practical terms, identifying a specific abrasive product with the term 60 Mesh would normally indicate that the product has a median size of the openings on a 60 mesh screen. The term 60 Grit more accurately identifies the particle size distribution of the product but the difference in terminology is insignificant for industry purposes. See our blog post Mesh vs. Grit for more detail.
The chart below shows the approximate size in inches and microns for various mesh sizes. These values are generally accepted as accurate but are approximates because the thickness of the wire used to make a specific screen will vary the number of openings in the one square inch. A micron is one-millionth of a meter or one-twenty-five thousandths of an inch. Most grades below 325 mesh are indicated by the micron size as these sizes are not manufactured using screens.
Powder Technology Incorporated (PTI) is a materials processing company with expertise in the total spectrum of particle modification with specialization in size reduction (including jet milling and hammer milling), air classification, vibratory screening and blending.
Sieving or screening is a method of categorizing a powders particle size by running the powder through a specific sized screen.* A powder can be separated into two or more size fractions by stacking the screens, thereby determining the powders particle size distribution. Sieves and screens are usually used for larger particle sized materials, greater than 44 micron (325 Mesh).
Two scales are used to classify particle sizes; US Sieve Series and Tyler Mesh Size. A powders mesh size can at times be somewhat confusing. A -6 mesh powder contains particles that pass through a 6 mesh screen. A -6 mesh powder has particles that measure less than 3360 microns. A powder that is -325 mesh has particles that measure less than 44 micron. As you can see, the larger the mesh number the smaller the particle size of the powder.
You would know that this powder passed though a 325 mesh screen. You could be confident that the powders particle size was less than 44 micron. However, much of the powder could be considerably less than 44 micron and still qualify as a -325 mesh powder. It could be 1 micron and qualify as -325 mesh, it could even be sub-micron and meet the -325 mesh specification. The designation -325 mesh is simply saying the powder passed through a 325 mesh screen.
This powder would have particles that were smaller than 40 mesh (420 micron) but larger than 100 Mesh (149 micron). The powder passed through the 40 mesh screen but was trapped in the 100 mesh screen. Larger particles were trapped above in the 40 mesh screen and smaller particles passed through the 100 mesh screen. As a result the larger particles were eliminated from the distribution by the 40 mesh screen and smaller particles were eliminated by the 100 mesh screen.
Sieve mesh sizes are based on dimensions of the mesh sizeopening, or on the number of openings per linear inch. The two major standards governingtest sieves and appropriate sizes are ASTM E11 and ISO 565/3310-1, both of which specify parameters for aperture dimensions, mesh size, and statistical variations. Opening sizes and mesh diameters for test sieves are often duplicated between these two standards, making it easier to select the proper sieve size for your material. The above tableis a list of all available sieves in U.S. and metric sizes for both ASTM E11 and ISO 565/3310-1. Sieve mesh opening sizes range from 5in (125mm) down to #635 (20m). The table outlines the standard, an alternate and the recommended sizes.
Gilson test sieves for particle size analysis of fine or coarse materials, soil, powder and other applicationsare available with brass or stainless steel frames fitted with brass or stainless steel cloth meeting ASTM or ISO standards. Common frame diameters, 3in (76mm), 8in (203mm), and 12in (305mm), as well as many ISO sizes in 200 mm and 300 mm frames, are in stock ready to ship. Other frame sizes such as 6in (152mm), 10in (254mm), and 18in (457mm) can be ordered. ASTM wire cloth is available cut-to-order or in bulk.