Reduced-Height Metric Hex Nuts Used as Jam Nuts for Vibration-Resistant Double-Nut Locking in Industrial Assemblies.
ISO 4035 Hexagon Thin Nuts are metric-series internally threaded fasteners with a reduced height (style 0, maximum height about 0.5D, well below a standard ISO 4032 regular nut) that serve as jam nuts assembled together with a regular or high nut in applications where vibration resistance, precise axial load control, or space constraints prevent the use of a full-height nut. ISO 4035 specifies steel property classes 04 and 05 and stainless classes such as A2-035 and A4-040 for thin nuts and covers all critical dimensional requirements including width across flats, width across corners, nut height, chamfer angle, and thread pitch for metric coarse pitch sizes M1.6 to M64, providing a globally recognized dimensional reference for thin hex nut procurement. These thin lock nuts are manufactured to ASTM A1082, the specification for high-strength stainless steel bolting material, which provides excellent corrosion resistance and reliable mechanical performance in marine and offshore structures, chemical process equipment, food-grade machinery, and water treatment infrastructure , where both the locking function and corrosion resistance of the nut are simultaneously critical to joint integrity. ISO 4035 thin nuts are commonly used as jam nuts tightened against ISO 4032 or ISO 4033 primary nuts to create a mechanically locked double-nut configuration that resists self-loosening under vibration without the need for thread-locking adhesives or mechanical locking inserts. Full EN 10204 Type 3.1 documentation is available for all ASTM A1082 ISO 4035 thin nut lots.
| Thread size d | P | da | dw | e | m | m´ | s | |||
|---|---|---|---|---|---|---|---|---|---|---|
| min. | max. | min. | min. | max. | min. | min. | max. | min. | ||
| M1.6 | 0.35 | 1.6 | 1.84 | 2.4 | 3.48 | 1 | 0.75 | 0.6 | 3.2 | 3.08 |
| M1.8 | 0.35 | 1.8 | 2.06 | 2.7 | 3.82 | 1.1 | 0.85 | 0.68 | 3.5 | 3.38 |
| M2 | 0.4 | 2 | 2.3 | 3.1 | 4.32 | 1.2 | 0.95 | 0.76 | 4 | 3.82 |
| M2.5 | 0.45 | 2.5 | 2.9 | 4.1 | 5.45 | 1.6 | 1.35 | 1.06 | 5 | 4.82 |
| M3 | 0.45 | 3 | 3.45 | 4.6 | 6.01 | 1.8 | 1.55 | 1.24 | 5.5 | 5.32 |
| M3.5 | 0.6 | 3.5 | 4 | 5.1 | 6.58 | 2 | 1.75 | 1.4 | 6 | 5.82 |
| M4 | 0.7 | 4 | 4.6 | 5.9 | 7.66 | 2.2 | 1.95 | 1.56 | 7 | 6.78 |
| M5 | 0.8 | 5 | 5.75 | 6.9 | 9.79 | 2.7 | 2.45 | 1.96 | 8 | 7.78 |
| M6 | 1 | 6 | 6.75 | 8.9 | 11.05 | 3.2 | 2.9 | 2.32 | 10 | 9.78 |
| M8 | 1.25 | 8 | 8.75 | 11.6 | 14.38 | 4 | 3.7 | 2.96 | 13 | 12.73 |
| M10 | 1.5 | 10 | 10.8 | 15.6 | 18.9 | 5 | 4.7 | 3.76 | 17 | 16.73 |
| M12 | 1.75 | 12 | 13 | 17.4 | 21.1 | 6 | 5.7 | 4.56 | 19 | 18.67 |
| M14 | 2 | 14 | 15.1 | 20.5 | 24.49 | 7 | 6.42 | 5.14 | 22 | 21.67 |
| M16 | 2 | 16 | 17.3 | 22.5 | 26.75 | 8 | 7.42 | 5.94 | 24 | 23.67 |
| M18 | 2.5 | 18 | 19.5 | 24.9 | 29.56 | 9 | 8.42 | 6.74 | 27 | 26.16 |
| M20 | 2.5 | 20 | 21.6 | 27.7 | 32.95 | 10 | 9.1 | 7.28 | 30 | 29.16 |
| M22 | 2.5 | 22 | 23.8 | 29.5 | 35.03 | 11 | 9.9 | 7.92 | 32 | 31 |
| M24 | 3 | 24 | 25.9 | 33.2 | 39.55 | 12 | 10.9 | 8.72 | 36 | 35 |
| M27 | 3 | 27 | 29.2 | 38 | 45.2 | 13.5 | 12.4 | 9.9 | 41 | 40 |
| M30 | 3.5 | 30 | 32.4 | 42.7 | 50.85 | 15 | 13.9 | 11.1 | 46 | 45 |
| M33 | 3.5 | 33 | 35.6 | 46.6 | 55.37 | 16.5 | 15.4 | 12.3 | 50 | 49 |
| M36 | 4 | 36 | 38.9 | 51.1 | 60.79 | 18 | 16.9 | 13.5 | 55 | 53.8 |
| M39 | 4 | 39 | 42.1 | 55.9 | 66.44 | 19.5 | 18.2 | 14.6 | 60 | 58.8 |
| M42 | 4.5 | 42 | 45.4 | 60 | 71.3 | 21 | 19.7 | 15.8 | 65 | 63.1 |
| M45 | 4.5 | 45 | 48.6 | 64.7 | 76.95 | 22.5 | 21.2 | 17 | 70 | 68.1 |
| M48 | 5 | 48 | 51.8 | 69.4 | 82.6 | 24 | 22.7 | 18.2 | 75 | 73.1 |
| M52 | 5 | 52 | 56.2 | 74.2 | 88.25 | 26 | 24.7 | 19.8 | 80 | 78.1 |
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 ISO 4035, 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).
