Inch-Series Corrosion-Resistant Lag Fasteners for Wood, Composite, and Structural Substrate Anchoring.
ASME B18.2.1 Hex Lag Screws are inch-series threaded fasteners featuring a hexagonal head and a coarse gimlet-point thread that is driven into a pilot hole in wood, sized from the thread root diameter (hard woods need a larger pilot hole than soft woods), making them the standard heavy-duty fastener for structural timber connections, deck framing, fence posts, marine dock structures, and outdoor construction applications where a screw-type fastener must develop high withdrawal and lateral load resistance directly in the base material. The ASME B18.2.1 standard covers dimensional requirements for hex lag screws ranging from No. 10 to 1-1/4 inch diameter, defining body diameter, head dimensions, width across flats, head height, thread length, and lag screw thread dimensions (major diameter, root diameter, threads per inch) with all associated manufacturing tolerances to ensure consistent dimensional performance. When manufactured to ASTM A1082, the specification for high-strength stainless steel bolting material, these hex lag screws provide outstanding corrosion resistance in outdoor, marine, and chemical environments where conventional galvanized or hot-dip zinc-coated lag screws would fail prematurely due to corrosion of the zinc coating in aggressive saline, acidic timber preservative, or high-humidity conditions. This makes ASTM A1082 stainless steel lag screws the preferred choice for coastal construction, marine dock assemblies, pressure-treated timber structures, swimming pool surrounds, and chemical plant grating installations. ASTM A1082 hex lag screws are available with EN 10204 Type 3.1 material certification for specification-controlled projects.
| Nominal Size or Basic Product Diameter | Body or Shoulder Diameter, E | Width Across Flats, F | Width Across Corners, G | Head Height, H | Minimum Shoulder Length, S | Radius of Fillet, R | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Max. | Min. | Basic | Max. | Min. | Max. | Min. | Basic | Max. | Min. | Max. | Min. | |||
| #10 | 4.826 | 5.055 | 4.521 | 7.144 | 7.137 | 6.883 | 8.204 | 7.849 | 3.175 | 3.556 | 2.794 | 2.388 | 0.762 | 0.254 |
| 1/4 | 6.350 | 6.604 | 6.020 | 11.113 | 11.125 | 10.795 | 12.827 | 12.294 | 4.366 | 4.775 | 3.810 | 2.388 | 0.762 | 0.254 |
| 5/16 | 7.938 | 8.230 | 7.569 | 12.700 | 12.700 | 12.294 | 14.656 | 14.021 | 5.556 | 5.969 | 4.953 | 3.175 | 0.762 | 0.254 |
| 3/8 | 9.525 | 9.855 | 9.144 | 14.288 | 14.275 | 13.818 | 16.510 | 15.748 | 6.350 | 6.807 | 5.740 | 3.175 | 0.762 | 0.254 |
| 7/16 | 11.113 | 11.481 | 10.693 | 15.875 | 15.875 | 15.316 | 18.339 | 17.450 | 7.541 | 8.026 | 6.909 | 3.962 | 0.762 | 0.254 |
| 1/2 | 12.700 | 13.081 | 12.243 | 19.050 | 19.050 | 18.415 | 21.996 | 20.980 | 8.731 | 9.246 | 7.671 | 3.962 | 0.762 | 0.254 |
| 5/8 | 15.875 | 16.307 | 15.367 | 23.813 | 23.825 | 23.012 | 27.508 | 26.238 | 10.716 | 11.278 | 9.601 | 7.925 | 1.524 | 0.508 |
| 3/4 | 19.050 | 19.507 | 18.517 | 28.575 | 28.575 | 27.635 | 32.995 | 31.496 | 12.700 | 13.310 | 11.557 | 9.525 | 1.524 | 0.508 |
| 7/8 | 22.225 | 22.733 | 21.641 | 33.338 | 33.325 | 32.233 | 38.506 | 36.754 | 14.684 | 15.342 | 13.487 | 9.525 | 1.524 | 0.508 |
| 1 | 25.400 | 25.959 | 24.790 | 38.100 | 38.100 | 36.830 | 43.993 | 41.986 | 17.066 | 17.780 | 15.011 | 15.875 | 2.286 | 0.762 |
| 1 1/8 | 28.575 | 29.185 | 27.889 | 42.863 | 42.875 | 41.427 | 49.505 | 47.219 | 19.050 | 19.812 | 16.713 | 15.875 | 2.286 | 0.762 |
| 1 1/4 | 31.750 | 32.436 | 31.064 | 47.625 | 47.625 | 46.025 | 54.991 | 52.476 | 21.431 | 22.250 | 19.025 | 15.875 | 2.286 | 0.762 |
| Nominal Length | Nominal Size (inches) | |||||
|---|---|---|---|---|---|---|
| 1/4 to 3/8 | 7/16 and 1/2 | 9/16 to 3/4 | 7/8 and 1 | 1 1/8 to 1 1/2 | Over 1 1/2 | |
| Up to 25.4 mm, incl. | +0.000 0.762 |
+0.000 0.762 |
+0.000 0.762 |
... | ... | ... |
| Over 25.4 mm to 63.5 mm, incl. | +0.000 1.016 |
+0.000 1.524 |
+0.000 2.032 |
+0.000 2.540 |
+0.000 3.048 |
+0.000 4.572 |
| Over 63.5 mm to 101.6 mm, incl. | +0.000 1.524 |
+0.000 2.032 |
+0.000 2.540 |
+0.000 3.556 |
+0.000 4.064 |
+0.000 5.080 |
| Over 101.6 mm to 152.4 mm, incl. | +0.000 2.540 |
+0.000 2.540 |
+0.000 2.540 |
+0.000 4.064 |
+0.000 4.572 |
+0.000 5.588 |
| Longer than 152.4 mm | +0.000 4.572 |
+0.000 4.572 |
+0.000 4.572 |
+0.000 5.080 |
+0.000 5.588 |
+0.000 6.096 |
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 B18.2.1, 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).
