Flattened Expanded Metal manufactured to DIN 791 follows the specification table reproduced on this page. The standard fixes geometry and tolerances; alloy chemistry and testing are assigned by their own companion documents.
DIN 791 — Scope
DIN 791 specifies the designation system, dimensions and tolerances of flattened expanded metal — mesh count or nominal opening, wire diameter and the permissible aperture deviations. Alloy chemistry, mechanical testing and delivery condition are governed by separate documents in the same standards family.
Tolerance Classes
DIN 791 defines tolerance limits on the average aperture and on the maximum single aperture, tightening as the aperture gets finer. For test-sieve duty the tighter ISO 3310-1 tolerances apply instead of the general cloth tolerances — specify sieve grade explicitly if the mesh will be used for particle-size analysis.
Specifications Defined by DIN 791
| Mesh designation (SWD x LWD) | SWD (mm) | LWD (mm) | Strand width (mm) | Strand thickness (mm) | Open area (%) |
|---|---|---|---|---|---|
| 6x12 | 6 | 12 | 1.0 | 1.0 | 62 |
| 10x20 | 10 | 20 | 1.5 | 1.5 | 66 |
| 12.5x25 | 12.5 | 25 | 2.0 | 2.0 | 60 |
| 16x34 | 16 | 34 | 2.0 | 2.0 | 70 |
| 22x50 | 22 | 50 | 3.0 | 3.0 | 67 |
Companion Standards
DIN 791 controls the geometry of flattened expanded metal. Companions frequently cited alongside it: ISO 565 / ASTM E11 (test-sieve aperture series), ISO 3310-1 (test sieves of metal wire cloth), ISO 4783 (selection of wire and aperture combinations), ISO 9044 (industrial woven wire cloth), and ISO 2941 (collapse/burst rating for finished filter elements).
When to Specify DIN 791
DIN 791 remains common in European engineering and on legacy drawings; for new international programs reference the ISO equivalent alongside it.