Converting mesh to mm and inches

Converting mesh to mm and inches

What does mesh size mean?  

Figuring out mesh sizes is simple. All you do is count the number of openings in one inch of screen (the number of openings in a lineal inch measured from the center of one wire to a point one inch distant).  The number of openings is the mesh size.  So a 4-mesh screen means there are four little squares across one linear inch of screen (see fig.).  As the number describing the mesh size increases, the size of the particles decreases.   Higher numbers equal finer material.  Mesh size is not a precise measurement of particle size.

What do the minus (-) and plus (+) plus signs mean when describing mesh sizes?  

Here's the explanation:  

• -200 mesh means that you need all particles that pass through a 200 mesh,
• +200 mesh means, that you need all particles that remain on the sieve of 200 mesh.

If you needed a ground mica that was closer to size you would need to specify two mesh sizes. For example: ground mica -40+100 Mesh. This mica powder would have particles that were smaller than 40 mesh (420 micron) but larger than 100 Mesh (149 micron).  The customer receives a powder having a particle passed through the 40 mesh screen but was trapped in the 100 mesh screen. Rejected are larger particles (were trapped above in the 40 mesh screen) and smaller particles (passed through the 100 mesh screen). 

How fine do screens get?  

That depends on the wire thickness.  If you think about it, the finer the weave, the closer the wires get together, eventually leaving no space between them at all. For this reason, beyond 325-mesh particle size is usually described in “microns.”