40 mesh denotes 40 wires per inch in each direction. For plain weave wire mesh the governing document is ISO 9044 / ASTM E2016; the specification row, aperture-micron conversion and selection guidance for this count follow.
40 Mesh Specification Row (ISO 9044 / ASTM E2016)
| Mesh count | Wire diameter (mm) | Aperture (mm) | Micron rating (u00b5m) | Open area (%) | Weight SS (kg/mu00b2) | Reference standard |
|---|---|---|---|---|---|---|
| 40-Mesh | 0.250 | 0.385 | 385 | 36.8 | 1.29 | ISO 9044 |
40 Mesh to Micron & Aperture
| Openings per inch | 40 |
|---|---|
| Aperture (opening width) | 0.39 mm |
| Micron rating | 385 µm |
| Standard wire diameter | 0.25 mm |
| Open area | 36.8 % |
Aperture = (25.4 mm ÷ mesh count) − wire diameter. The micron rating equals the aperture in micrometres; actual retention also depends on particle shape and cake formation.
Wire Diameter Options at 40 Mesh
| Option | Wire dia | Aperture | Micron | Open area | Weight (SS) |
|---|---|---|---|---|---|
| Heavy wire | 0.325 mm | 0.310 mm | 310 µm | 23.8 % | 2.18 kg/m² |
| Standard wire | 0.250 mm | 0.385 mm | 385 µm | 36.8 % | 1.29 kg/m² |
| Fine wire | 0.188 mm | 0.448 mm | 448 µm | 49.7 % | 0.72 kg/m² |
Heavier wire adds strength and abrasion life but closes the aperture; finer wire opens the aperture and raises throughput at the cost of durability. Specify mesh count AND wire diameter to fix the aperture unambiguously.
Open Area & Flow at 40 Mesh
The standard 40 mesh weave presents an open area of about 36.8%. At this count the mesh presents little flow resistance; selection is normally driven by particle retention and mechanical strength rather than pressure drop.
40 Mesh Cloth Weight
Standard 40 mesh stainless cloth weighs approximately 1.29 kg/m² (density 7.93 g/cm³ basis; brass and copper weave roughly 10% heavier, aluminum about one third). Use this figure for roll handling and freight estimation.
Typical Applications for 40 Mesh Plain Weave Wire Mesh
40 mesh plain weave wire mesh is commonly specified for general straining and sieving, paint and coating filtration, grease filters, insect screening, grain cleaning and pre-filtration ahead of fine media.
Plain, Twill or Dutch Weave at This Rating?
Plain square weave is the standard at this count: every opening is a true square of the stated aperture, retention is absolute for hard spherical particles, and the cloth is easy to clean.
When to Step Up or Down from 40 Mesh
Move to 50 mesh when particles are passing that must be retained; drop back to 30 mesh when the element blinds too quickly or the pressure drop is excessive. In a multi-layer pack, pair this count with a coarser support mesh downstream to carry the pressure load.
