ASME B18.2.1 Square Bolts
Scope
ASME B18.2.1 Square Bolts dimension standard covers the dimensional requirements for product types of bolts and screws recognized as American National Standard. Also included are appendices covering gaging procedures, grade markings for bolts and screws, formulas on which dimensional data are based, and a specification to assist in identifying a product as being a screw or a bolt. Where questions arise concerning acceptance of product, the dimensions in the tables shall govern over recalculation by formula. Heavy hex structural bolts, formerly covered in ASME B18.2.1, are now covered in ASME B18.2.6, The Tables measurements are also converted into millimeters to make the information clearer and easier to to understand.
ASME B18.2.1 Square Bolts Dimensions (mm)
| Nominal Size or Basic Product Diameter | Full-Size Body Diameter, E | Width Across Flats, F | Width Across Corners, G | Head Height, H | Radius of Fillet, R | Nominal Thread Length, LT | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Max. | Min. | Basic | Max. | Min. | Max. | Min. | Basic | Max. | Min. | Max. | Min. | 152.4mm and Shorter | Over 152.4mm | ||
| 1/4 | 6.350 | 6.604 | 6.020 | 9.525 | 9.525 | 9.195 | 13.462 | 12.649 | 4.366 | 4.775 | 3.962 | 0.762 | 0.254 | 19.050 | 25.400 |
| 5/16 | 7.938 | 8.230 | 7.569 | 12.700 | 12.700 | 12.294 | 17.958 | 16.891 | 5.159 | 5.588 | 4.724 | 0.762 | 0.254 | 22.225 | 28.575 |
| 3/8 | 9.525 | 9.855 | 9.144 | 14.288 | 14.275 | 13.818 | 20.193 | 18.974 | 6.350 | 6.807 | 5.893 | 0.762 | 0.254 | 25.400 | 31.750 |
| 7/16 | 11.113 | 11.481 | 10.693 | 15.875 | 15.875 | 15.316 | 22.454 | 21.031 | 7.541 | 8.026 | 7.061 | 0.762 | 0.254 | 28.575 | 34.925 |
| 1/2 | 12.700 | 13.081 | 12.243 | 19.050 | 19.050 | 18.415 | 26.949 | 25.273 | 8.334 | 8.839 | 7.823 | 0.762 | 0.254 | 31.750 | 38.100 |
| 5/8 | 15.875 | 16.307 | 15.367 | 23.813 | 23.825 | 23.012 | 33.680 | 31.598 | 10.716 | 11.278 | 10.160 | 1.524 | 0.508 | 38.100 | 44.450 |
| 3/4 | 19.050 | 19.507 | 18.517 | 28.575 | 28.575 | 27.635 | 40.411 | 37.948 | 12.700 | 13.310 | 12.090 | 1.524 | 0.508 | 44.450 | 50.800 |
| 7/8 | 22.225 | 22.733 | 21.641 | 33.338 | 33.325 | 32.233 | 47.142 | 44.247 | 15.081 | 15.748 | 14.427 | 1.524 | 0.508 | 50.800 | 57.150 |
| 1 | 25.400 | 25.959 | 24.790 | 38.100 | 38.100 | 36.830 | 53.873 | 50.571 | 16.669 | 17.374 | 15.951 | 2.286 | 0.762 | 57.150 | 63.500 |
| 1 1/8 | 28.575 | 29.185 | 27.889 | 42.863 | 42.875 | 41.427 | 60.604 | 56.871 | 19.050 | 19.812 | 18.288 | 2.286 | 0.762 | 63.500 | 69.850 |
| 1 1/4 | 31.750 | 32.436 | 31.064 | 47.625 | 47.625 | 46.025 | 67.361 | 63.221 | 21.431 | 22.250 | 20.625 | 2.286 | 0.762 | 69.850 | 76.200 |
| 1 3/8 | 34.925 | 35.662 | 34.163 | 52.388 | 52.375 | 50.648 | 74.092 | 69.545 | 23.019 | 23.876 | 22.149 | 2.286 | 0.762 | 76.200 | 82.550 |
| 1 1/2 | 38.100 | 38.887 | 37.338 | 57.150 | 57.150 | 55.245 | 80.823 | 75.844 | 25.400 | 26.314 | 24.486 | 2.286 | 0.762 | 82.550 | 88.900 |
ASME B18.2.1 Square Bolts 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. | +0.508 0.762 |
+0.508 0.762 |
+0.508 0.762 |
... | ... | ... |
| Over 25.4 mm to 63.5 mm, incl. | +0.508 1.016 |
+1.016 1.524 |
+1.524 2.032 |
+2.032 2.54 |
+3.048 3.048 |
+4.572 4.572 |
| Over 63.5 mm to 101.6 mm, incl. | +1.016 1.524 |
+1.524 2.032 |
+2.032 2.54 |
+2.54 3.556 |
+4.064 4.064 |
+5.08 5.08 |
| Over 101.6 mm to 152.4 mm, incl. | +1.524 2.54 |
+2.032 2.54 |
+2.54 2.54 |
+3.048 4.064 |
+4.572 4.572 |
+5.588 5.588 |
| Longer than 152.4 mm | +2.54 4.572 |
+3.048 4.572 |
+3.556 4.572 |
+4.064 5.08 |
+5.588 5.588 |
+6.096 6.096 |
ASME B18.2.1 Square Bolts Dimensions (inch)
| Nominal Size or Basic Product Diameter | Full-Size Body Diameter, E | Width Across Flats, F | Width Across Corners, G | Head Height, H | Radius of Fillet, R | Nominal Thread Length for Bolt Lengths, LT | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Max. | Min. | Basic | Max. | Min. | Max. | Min. | Basic | Max. | Min. | Max. | Min. | 6 in. and Shorter | Over 6 in. | ||
| 1/4 | 0.2500 | 0.260 | 0.237 | 3/8 | 0.375 | 0.362 | 0.530 | 0.498 | 11/64 | 0.188 | 0.156 | 0.03 | 0.01 | 0.750 | 1.000 |
| 5/16 | 0.3125 | 0.324 | 0.298 | 1/2 | 0.500 | 0.484 | 0.707 | 0.665 | 13/64 | 0.220 | 0.186 | 0.03 | 0.01 | 0.875 | 1.125 |
| 3/8 | 0.3750 | 0.388 | 0.360 | 9/16 | 0.562 | 0.544 | 0.795 | 0.747 | 1/4 | 0.268 | 0.232 | 0.03 | 0.01 | 1.000 | 1.250 |
| 7/16 | 0.4375 | 0.452 | 0.421 | 5/8 | 0.625 | 0.603 | 0.884 | 0.828 | 19/64 | 0.316 | 0.278 | 0.03 | 0.01 | 1.125 | 1.375 |
| 1/2 | 0.5000 | 0.515 | 0.482 | 3/4 | 0.750 | 0.725 | 1.061 | 0.995 | 21/64 | 0.348 | 0.308 | 0.03 | 0.01 | 1.250 | 1.500 |
| 5/8 | 0.6250 | 0.642 | 0.605 | 15/16 | 0.938 | 0.906 | 1.326 | 1.244 | 27/64 | 0.444 | 0.400 | 0.06 | 0.02 | 1.500 | 1.750 |
| 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 | 0.06 | 0.02 | 1.750 | 2.000 |
| 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 | 0.06 | 0.02 | 2.000 | 2.250 |
| 1 | 1.0000 | 1.022 | 0.976 | 1 1/2 | 1.500 | 1.450 | 2.121 | 1.991 | 21/32 | 0.684 | 0.628 | 0.09 | 0.03 | 2.250 | 2.500 |
| 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 | 0.09 | 0.03 | 2.500 | 2.750 |
| 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 | 0.09 | 0.03 | 2.750 | 3.000 |
| 1 3/8 | 1.3750 | 1.404 | 1.345 | 2 1/16 | 2.062 | 1.994 | 2.917 | 2.738 | 29/32 | 0.940 | 0.872 | 0.09 | 0.03 | 3.000 | 3.250 |
| 1 1/2 | 1.5000 | 1.531 | 1.470 | 2 1/4 | 2.250 | 2.175 | 3.182 | 2.986 | 1 | 1.036 | 0.964 | 0.09 | 0.03 | 3.250 | 3.500 |
ASME B18.2.1 Square Bolts Length Tolerance (Inch)
| Nominal Length | Nominal Size | |||||
|---|---|---|---|---|---|---|
| 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 1 in., incl. | +0.02 0.03 |
+0.02 0.03 |
+0.02 0.03 |
... | ... | ... |
| Over 1 in. to 2 1/2 in., incl. | +0.02 0.04 |
+0.04 0.06 |
+0.06 0.08 |
+0.08 0.10 |
+0.12 0.12 |
+0.18 0.18 |
| Over 2 1/2 in. to 4 in., incl. | +0.04 0.06 |
+0.06 0.08 |
+0.08 0.10 |
+0.10 0.14 |
+0.16 0.16 |
+0.20 0.20 |
| Over 4 in. to 6 in., incl. | +0.06 0.10 |
+0.08 0.10 |
+0.10 0.10 |
+0.12 0.16 |
+0.18 0.18 |
+0.22 0.22 |
| Longer than 6 in. | +0.10 0.18 |
+0.12 0.18 |
+0.14 0.18 |
+0.16 0.20 |
+0.22 0.22 |
+0.24 0.24 |
ASME Material Specifications
ASTM
A193/A193M Standard Specification for Alloy-Steel and Stainless Steel Bolting Materials for
High Temperature or High Pressure Service and Other Special Purpose Applications
ASTM
A307 Standard Specification for Carbon Steel Bolts and Studs, 60 000 PSI Tensile
Strength
ASTM
A449 Standard Specification for Hex Cap Screws, Bolts and Studs, Steel, Heat Treated,
120/105/90
ksi Minimum Tensile Strength
ASTM
A453/A453M Standard Specification for Bolting, Stud Bolts, Screws, Nuts
ASTM A354 Standard
Specification for Quenched and Tempered Alloy Steel Bolts, Studs, and Other Externally Threaded
Fasteners
ASTM
A320 Standard Specification for Alloy-Steel and Stainless Steel Bolting for Low-Temperature
Service
ASTM
A1082/A1082M Standard Specification for Bolting, Stud Bolts, Screws, Nuts
ASTM
A1014/A1014M Standard Specification for UNS N07718 Bolting, Stud Bolts, Screws, Nuts
ASTM
F468 Standard Specification for Nonferrous Bolts, Hex Cap Screws, and Studs
ASTM
F593 Standard Specification for Stainless Steel Bolts, Hex Cap Screws, and Studs
ASTM
F901 Aluminium Transmission Tower Bolts
ASTM F738
Stud Bolts, Screws
ASTM F1554
Anchor Bolts, Anchor Rods
ASTM
F2281 Bolting, Stud Bolts, Screws, Hex Cap Screws, Threaded Rods
ASTM
F3125 Heavy Hex Bolts, Screws, Studs