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NF E 25-511 — French Serrated Lock Washers
NF E 25-511French standard for serrated lock washers. Defines Type Z (fine knurl), Type M (medium knurl), Type L (coarse knurl). Serrations cold-stamped; washer embeds into mating surfaces to provide anti-loosening. Material XC75 (C75S)/XC65, surface phosphated or zinc-plated. Mainly used in automotive, agricultural machinery, and general mechanical assembly.
Clause Summaries
Knurl Type Classification & Selection
Type Z (fine): pitch 0.5-1.0mm, for hard surfaces (HRC 30-45). Type M (medium): pitch 0.8-1.2mm, general purpose. Type L (coarse): pitch 1.2-2.0mm, for soft substrates (castings/aluminum).
Dimensions & Tolerances
Covers M2-M30 thread sizes. OD tolerance h14, ID H14, thickness ±0.05mm (t≤1mm) or ±0.1mm (t>1mm). Knurl depth ≥0.1mm.
Dimension Table
| de | di | force | group | h0 | t | weight_per_1000 |
|---|---|---|---|---|---|---|
| 9 | 4.3 | 560 | M4-Z | 0.2 | 0.8 | 0.22 |
| 12 | 6.4 | 1100 | M6-M | 0.3 | 1 | 0.48 |
| 16 | 8.4 | 1800 | M8-M | 0.4 | 1.2 | 0.85 |
| 20 | 10.5 | 2800 | M10-L | 0.5 | 1.5 | 1.55 |
| 24 | 13 | 4200 | M12-L | 0.6 | 1.8 | 2.7 |
| 30 | 17 | 7000 | M16-L | 0.75 | 2.2 | 5.2 |