Precision Regular-Height Metric Hex Nuts for Standard Metric Bolted Assemblies Across Industrial and Structural Applications.
ASME B18.2.4.1M Metric Hex Nuts Style 1 are metric-series regular hexagon internally threaded fasteners providing dimensional requirements in SI units for width across flats, width across corners, nut height, chamfer dimensions, and thread pitch specifications (Class 6H) for sizes M1.6 through M36, serving as the standard mating nut for ASME B18.2.3.1M metric hex cap screws, B18.2.3.5M metric hex bolts, and B18.31.1M metric clamping studs in North American-designed systems operating under metric fastener standards. The ASME B18.2.4.1M Style 1 dimensional reference ensures full interchangeability between metric hex nut suppliers across different manufacturing countries, which is essential for large international engineering projects and global maintenance programs sourcing metric fasteners from multiple vendors. When manufactured to ASTM A1082, the specification for high-strength stainless steel bolting material, these Style 1 metric hex nuts provide excellent corrosion resistance and maintained mechanical performance in aggressive service environments, making them the preferred choice for chemical processing plants, food and beverage facilities, marine structures, water treatment infrastructure, and pharmaceutical manufacturing buildings. Proper nut grade selection to match the bolt material specification is essential to achieving safe, reliable, and code-compliant bolted joint performance in all metric fastening applications. ASTM A1082 metric hex nuts are available with EN 10204 Type 3.1 material certification for traceable quality-assured supply.
| Nominal Dia. | S | E | M | Dw | C | Total Runout of Bearing Surface FIM | ||||
|---|---|---|---|---|---|---|---|---|---|---|
| Width Across Flats | Width Across Corners | Thickness | Bearing Face Dia | Washer Face Thickness | ||||||
| Max. | Min. | Max. | Min. | Max. | Min. | Min. | Max. | Min. | Max. | |
| M1.6 | 3.20 | 3.02 | 3.70 | 3.41 | 1.30 | 1.05 | 2.3 | ... | ... | ... |
| M2 | 4.00 | 3.82 | 4.62 | 4.32 | 1.60 | 1.35 | 3.1 | ... | ... | ... |
| M2.5 | 5.00 | 4.82 | 5.77 | 5.45 | 2.00 | 1.75 | 4.1 | ... | ... | ... |
| M3 | 5.50 | 5.32 | 6.35 | 6.01 | 2.40 | 2.15 | 4.6 | ... | ... | ... |
| M3.5 | 6.00 | 5.82 | 6.93 | 6.58 | 2.80 | 2.55 | 5.1 | ... | ... | ... |
| M4 | 7.00 | 6.78 | 8.08 | 7.66 | 3.20 | 2.90 | 6.0 | ... | ... | ... |
| M5 | 8.00 | 7.78 | 9.24 | 8.79 | 4.70 | 4.40 | 7.0 | ... | ... | 0.30 |
| M6 | 10.00 | 9.78 | 11.55 | 11.05 | 5.20 | 4.90 | 8.9 | ... | ... | 0.33 |
| M8 | 13.00 | 12.73 | 15.01 | 14.38 | 6.80 | 6.44 | 11.6 | ... | ... | 0.36 |
| M10 | 15.00 | 14.73 | 17.32 | 16.64 | 9.10 | 8.70 | 13.6 | ... | ... | 0.39 |
| M10 | 16.00 | 15.73 | 18.45 | 17.77 | 8.40 | 8.04 | 14.6 | ... | ... | 0.39 |
| M12 | 18.00 | 17.73 | 20.78 | 20.03 | 10.80 | 10.37 | 16.6 | ... | ... | 0.42 |
| M14 | 21.00 | 20.67 | 24.25 | 23.35 | 12.80 | 12.10 | 19.4 | ... | ... | 0.45 |
| M16 | 24.00 | 23.67 | 27.71 | 26.75 | 14.80 | 14.10 | 22.4 | ... | ... | 0.48 |
| M20 | 30.00 | 29.16 | 34.64 | 32.95 | 18.00 | 16.90 | 27.9 | 0.8 | 0.4 | 0.56 |
| M24 | 36.00 | 35.00 | 41.57 | 39.55 | 21.50 | 20.20 | 32.5 | 0.8 | 0.4 | 0.64 |
| M30 | 46.00 | 45.00 | 53.12 | 50.85 | 25.60 | 24.30 | 42.5 | 0.8 | 0.4 | 0.76 |
| M36 | 55.00 | 53.80 | 63.51 | 60.79 | 31.00 | 29.40 | 50.8 | 0.8 | 0.4 | 0.89 |
ASTM A1082/A1082M (2016) Table 1 lists 14 duplex (ferritic-austenitic) grades, S31100, S31260, S31803, S32101, S32202, S32205 (2205), S32304 (2304), S32506, S32550 (255), S32750 (2507), S32760, S32906, S32950 and S39277, and 5 precipitation-hardening grades, S15700 (Type 632), S17400 (Type 630), S17600 (Type 635), S17700 (Type 631) and S35500 (Type 634). Grade selection depends on design, service conditions and the mechanical properties required.
Dimensions follow ASME B18.2.4.1M, tabulated on this page. ASTM A1082/A1082M sets chemistry (Table 1), heat treatment and mechanical properties (Tables 2 to 4) and marking (Table 5). ASTM A962/A962M general requirements also apply, and A1082 prevails where the two conflict (clause 4.1). Inch-pound units apply unless the order specifies A1082M (clause 1.4).
ISO 15156-3 Table A.24 accepts wrought duplex stainless steel for any equipment when it is solution-annealed and liquid-quenched or rapidly cooled, has 35 % to 65 % ferrite and has had no ageing heat treatment. With 30 ≤ PREN ≤ 40 and Mo ≥ 1.5 % the limit is 232 °C (450 °F) and 10 kPa (1.5 psi) H2S partial pressure; with 40 < PREN ≤ 45 it is 232 °C (450 °F) and 20 kPa (3 psi). Table A.27 accepts wrought 17-4 PH (S17400) at 33 HRC max after a double age at 620 °C (1150 °F) or a modified double age, for named wellhead, valve and subsurface components, up to 3.4 kPa (0.5 psi) H2S and pH 4.5 or above.
Two supplementary requirements apply to nuts when the purchaser specifies them. S5 requires proof load testing of nuts, with the number of tests and the proof loads agreed between purchaser and manufacturer. S6 requires cross-sectional hardness testing of nuts per ASTM A370 Annex A3, with the number of tests agreed. Certification reports chemical analysis, mechanical tests and the heat treatment method (clause 10.1).
Table 4: solution annealed at 1880 to 2060 °F [1025 to 1125 °C], water quenched. Up to and including 2 in.: tensile 116 ksi [800 MPa] and yield 80 ksi [550 MPa] min. Over 2 in.: 110 ksi [760 MPa] and 75 ksi [515 MPa] min. Elongation 15 % min and hardness 33 HRC or 310 HB max for both. The marking grade symbol is 32750 (Table 5).
