Versatile Metric Small Fasteners for Precision Electronics, Instrumentation, and Corrosion-Sensitive Industrial Assemblies.
ASME B18.6.7M Metric Hex Head Machine Screws are metric-series small fasteners designed to thread into pre-tapped holes or pair with metric nuts for securing components in electronics, control panels, scientific instruments, small mechanical assemblies, household appliances, and light industrial equipment where compact fastening and precise dimensional control are critical design requirements. The ASME B18.6.7M standard governs metric dimensions for multiple head styles, including flat countersunk, oval countersunk, pan, hex, and hex flange heads, covering head dimensions, recess or slot dimensions, body diameter, thread pitch, thread length, and associated tolerances in SI units for sizes M2 through M12. These metric machine screws are manufactured to ASTM A1082, the specification for high-strength stainless steel bolting material, which provides outstanding corrosion resistance and aesthetic surface quality required in medical devices, food-grade equipment, marine instrument panels, pharmaceutical packaging machinery, and chemical plant control cabinets. Unless otherwise specified by the purchaser, ASME B18.6.7M machine screw threads are metric coarse series to ASME B1.13M, with Class 6g size limits before plating or coating. Full EN 10204 Type 3.1 material documentation is available for ASTM A1082 metric machine screws supplied to quality-critical projects in medical, aerospace, and industrial sectors.
| Nominal Size and Thread Pitch | DS | Sa | Ea | K | DA | R | |||
|---|---|---|---|---|---|---|---|---|---|
| Body Diameter | Hex Width Across Flats | Hex Width Across Corners | Head Height | Underhead Fillet | |||||
| Transition Dia | Radius | ||||||||
| Max | Min | Max | Min | Min | Max | Min | Max | Min | |
| M2 × 0.4 | 2 | 1.65 | 3.2 | 3.02 | 3.38 | 1.6 | 1.3 | 2.6 | 0.1 |
| M2.5 × 0.45 | 2.5 | 2.12 | 4 | 3.82 | 4.28 | 2.1 | 1.8 | 3.1 | 0.1 |
| M3 × 0.5 | 3 | 2.58 | 5 | 4.82 | 5.4 | 2.3 | 2 | 3.6 | 0.1 |
| M3.5 × 0.6 | 3.5 | 3 | 5.5 | 5.32 | 5.96 | 2.6 | 2.3 | 4.1 | 0.1 |
| M4 × 0.7 | 4 | 3.43 | 7 | 6.78 | 7.59 | 3 | 2.6 | 4.7 | 0.2 |
| M5 × 0.8 | 5 | 4.36 | 8 | 7.78 | 8.71 | 3.8 | 3.3 | 5.7 | 0.2 |
| M6 × 1 | 6 | 5.21 | 10 | 9.78 | 10.95 | 4.7 | 4.1 | 6.8 | 0.3 |
| M8 × 1.25 | 8 | 7.04 | 13 | 12.73 | 14.26 | 6 | 5.2 | 9.2 | 0.4 |
| M10 × 1.5 | 10 | 8.86 | 16 | 15.73 | 17.62 | 7.5 | 6.5 | 11.2 | 0.4 |
| M12 × 1.75 | 12 | 10.68 | 18 | 17.73 | 19.86 | 9 | 7.8 | 13.2 | 0.4 |
| M10 × 1.5b | 10 | 8.86 | 15 | 14.73 | 16.5 | 7.5 | 6.5 | 11.2 | 0.4 |
|
|||||||||
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 B18.6.7M, 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.
The grade symbol comes from Table 5 (clause 11.1), for example 32205 for S32205 or 174G for S17400 in H1150. With Supplementary Requirement S2 the marking goes on the heads of bolts of all sizes; if the area is too small, the grade symbol may go on one end and the manufacturer's identification on the other. Bolts under 1/4 in. [6 mm] are marked by agreement between purchaser and manufacturer.
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).
