ASME B18.2.1 Square Lag Screws

ASME B18.2.1 Square Lag Screws

Dimensions of Square Lag Screws

Nominial 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.
No. 10
0.1900
0.199 0.178 9/32 0.281 0.271 0.398 0.372 1/8 0.140 0.110 0.094 0.03 0.01
1/4
0.2500
0.260 0.237 3/8 0.375 0.362 0.530 0.498 11/64 0.188 0.156 0.094 0.03 0.01
5/16
0.3125
0.324 0.298 1/2 0.500 0.484 0.707 0.665 13/64 0.220 0.186 0.125 0.03 0.01
3/8
0.3750
0.388 0.360 9/16 0.562 0.544 0.795 0.747 1/4 0.268 0.232 0.125 0.03 0.01
7/16
0.4375
0.452 0.421 5/8 0.625 0.603 0.884 0.828 19/64 0.316 0.278 0.156 0.03 0.01
1/2
0.5000
0.515 0.482 3/4 0.750 0.725 1.061 0.995 21/64 0.348 0.308 0.156 0.03 0.01
5/8
0.6250
0.642 0.605 15/16 0.938 0.906 1.326 1.244 27/64 0.444 0.400 0.312 0.06 0.02
3/4
0.7500
0.768 0.729 1 1/8 1.125 1.088 1.591 1.494 1/2 0.524 0.476 0.375 0.06 0.02
7/8
0.8750
0.895 0.852 1 5/16 1.312 1.269 1.856 1.742 19/32 0.620 0.568 0.375 0.06 0.02
1
1.0000
1.022 0.976 1 1/2 1.500 1.450 2.121 1.991 21/32 0.684 0.628 0.625 0.09 0.03
1 1/8
1.1250
1.149 1.098 1 11/16 1.688 1.631 2.386 2.239 3/4 0.780 0.720 0.625 0.09 0.03
1 1/4
1.2500
1.277 1.223 1 7/8 1.875 1.812 2.652 2.489 27/32 0.876 0.812 0.625 0.09 0.03

Dimensions of Screw Threads

Nomianal Size or Basic product Diameter Threads per inch. Major Diameter Root Diameter Length Tolerance
Max. Min. Max. Min. ≥ 6 in. > 6 in.
No. 10 0.190 11 0.199 0.178 0.122 0.107 ±0.12 ±0.25
1/4 0.250 10 0.260 0.237 0.177 0.160 ±0.12 ±0.25
5/16 0.312 9 0.324 0.298 0.228 0.210 ±0.12 ±0.25
3/8 0.375 7 0.388 0.360 0.268 0.250 ±0.12 ±0.25
1/2 0.500 6 0.515 0.482 0.374 0.354 ±0.12 ±0.25
5/8 0.625 5 0.642 0.605 0.473 0.453 ±0.25 ±0.25
3/4 0.750 4 1/2 0.768 0.729 0.582 0.562 ±0.25 ±0.25
7/8 0.875 4 0.895 0.852 0.686 0.665 ±0.25 ±0.25
1 1.000 3 1/2 1.022 0.976 0.784 0.760 ±0.25 ±0.25
1 1/8 1.125 3 1/4 1.149 1.100 0.892 0.867 ±0.25 ±0.25
1 1/4 1.250 3 1/4 1.277 1.223 1.017 0.987 ±0.25 ±0.25