Related Specifications
Surface Treatments
Certifications
- ISO 9001 - 2015 Certified
- PED 2014/68/EC
- NACE MR0175/ISO 15156-2
- NORSOK M-650
- DFAR
- MERKBLATT AD 2000 W2/W7/W10
ASME B18.2.1 Hex Lag Screws – Dimensions, Specifications & Standards
Dimensions, Tolerances & Material Specifications for Hex Lag Screws.
ASME B18.2.1 Hex Lag Screws are inch-series fasteners covering dimensional requirements for full-diameter and reduced-diameter body lag screws from No. 10 to 1-1/4 inch diameter, with an approximate 60° gimlet or cone point for installation into wood and other substrates. ASME B18.2.1 defines critical dimensions including head height, width across flats, body diameter, thread length, and tolerances — all recognized as American National Standards. These lag screws are used in conjunction with ASTM A1014/A1014M, the standard specification for UNS N07718 bolting, making them suitable for high-performance applications requiring superior corrosion resistance and strength. The standard also permits carbon steel per A307 Grade A, ASTM F593, and nonferrous materials per ASTM F468. ASME B18.2.1 governs only dimensions — chemistry and mechanical strength are addressed by the applicable ASTM or SAE grade specification.
ASME B18.2.1 Hex Lag Screws Dimensions (mm)
| 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 |
ASME B18.2.1 Hex Lag Screws Length Tolerance (mm)
| 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 |
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