ASTM A307 Bolts Grade A, B, Gr 307A Threaded Rod Tensile Yield Strength
ASTM A307 Bolts, Threaded Rod, Grade A, B
ASTM A307 bolts, threaded rod and studs, are the most commonly used fasteners, covering two grades of chemical and mechanical requirements from 0.25-4 inches in size.
- ASTM A307 Grade A: Suitable for bolts, studs and screws for general applications, with a minimum tensile strength of 60 ksi.
- ASTM A307 Grade B: Heavy-duty bolts, studs and screws, with a tensile strength of 60-100 ksi, used for flange connections in piping systems with cast iron flanges.
Note: This standard does not cover anchor bolt.
Product Marking
All A307 bolt heads, one end of studs 3/8 inches and larger, and studs smaller than 3/8 inches when feasible should be marked with the following grade mark:
- Grade A: 307A
- Grade B: 307B
A307 threaded rod shall be exempt from the marking requirements of relevant material specifications, unless otherwise specified by the buyer. Packaging and labeling requirements are mandatory in the applicable material specifications. If markings are required, they should be located at both ends of the threaded rod and should be raised or lowered according to the manufacturer’s choice.
Specifications
The following tables show ASTM A307 bolt grade and threaded rod properties and specifications (datasheet) including chemical composition, mechanical properties, etc.
A307 Steel Chemical Composition
Chemical requirements for A307 steel, 307B and 307A bolt grade, threaded rod, and studs is listed in the following table.
| Chemical Requirements | |||||
| Grades | C | Mn | P | S | Condition |
| ASTM A307 Grade A | 0.29 | 1.2 | 0.04 | 0.15 | Heat Analysis |
| 0.33 | 1.25 | 0.041 | Product Analysis | ||
| ASTM A307 Grade B | 0.29 | 1.2 | 0.04 | 0.05 | Heat Analysis |
| 0.33 | 1.25 | 0.041 | 0.051 | Product Analysis | |
Mechanical Properties
Hardness Requirements for A307 Bolt, Stud, and Threaded Rod
| Hardness Requirements | |||
| Grade | Nominal Length, in. | Hardness | |
| Brinell | Rockwell B | ||
| A307 Gr A | Less than 3 x dia | 121-241 | 69-100 |
| 3 x dia and longer | ≤241 | ≤100 | |
| A307 Gr B | Less than 3 x dia | 121-212 | 69-95 |
| 3 x dia and longer | ≤212 | ≤95 | |
Tensile Requirements for Full-Size ASTM A307 Bolts, Studs, and Threaded Rod
| Tensile Requirements | ||||
| Bolt Size, in. | Threads per inch | Stress Area, in. | Tensile Strength, lbf x 103 (kN) | |
| Grade A, ≥ | Grade,B | |||
| 1/4 | 20 | 0.0318 | 1.9 (8.45) | 1.9-3.18 (8.45-14.16) |
| 5/16 | 18 | 0.0524 | 3.1 (13.79) | 3.1-5.24 (13.79-23.31) |
| 3/8 | 16 | 0.0775 | 4.65 (20.68) | 4.65-7.75 (20.68-34.47) |
| 7/16 | 14 | 0.1063 | 6.35 (28.25) | 6.35-10.63 (28.25-47.28) |
| 1/2 | 13 | 0.1419 | 8.5 (37.81) | 8.5-14.19 (37.81-63.12) |
| 9/16 | 12 | 0.182 | 11 (49) | 11-18.2 (49-81) |
| 5/8 | 11 | 0.226 | 13.55 (60) | 13.55-22.6 (60-100) |
| 3/4 | 10 | 0.334 | 20.05 (89) | 20.05-33.4 (89-148) |
| 7/8 | 9 | 0.462 | 27.7 (123) | 27.7-46.2 (123-205) |
| 1 | 8 | 0.606 | 36.35 (161) | 36.35-60.6 (161-269) |
| 1 1/8 | 7 | 0.763 | 45.8 (204) | 45.8-76.3 (204-339) |
| 1 1/4 | 7 | 0.969 | 58.15 (230) | 58.15-96.9 (230-431) |
| 1 3/8 | 6 | 1.155 | 69.3 (308) | 69.3-115.5 (308-514) |
| 1 1/2 | 6 | 1.405 | 84.3 (375) | 84.3-140.5 (375-625) |
| 1 3/4 | 5 | 1.9 | 114 (507) | 114-190 (507-845) |
| 2 | 4 1/2 | 2.5 | 150 (667) | 150-250 (667-1112) |
| 2 1/4 | 4 1/2 | 3.25 | 195 (867) | 195-325 (867-1445) |
| 2 1/2 | 4 | 4 | 240 (1067) | 240-400 (1067-1779) |
| 2 3/4 | 4 | 4.93 | 295.8 (1316) | 295.8-493 (1316-2193) |
| 3 | 4 | 5.97 | 358.2 (1593) | 358.2-597 (1593-2655) |
| 3 1/4 | 4 | 7.1 | 426 (1895) | 426-710 (1895-3158) |
| 3 1/2 | 4 | 8.33 | 499.8 (2223) | 499.8-833 (2223-3705) |
| 3 3/4 | 4 | 9.66 | 579.6 (2578) | 579.6-966 (2578-4297) |
| 4 | 4 | 11.08 | 664.8 (2957) | 664.8-1,108 (2957-4928) |
| Tensile Requirements for Machined Specimens | |||
| Grades | Tensile strength, ksi | Yield point, min ksi | Elongation in 2 in, % |
| ASTM A307 Gr A | 60, ≥ | – | 18 |
| ASTM A307 Gr B | 60-100 | – | 18 |
For inspection the sample size and acceptance number of hot-dipped or mechanically deposited zinc-coated threads
| Lot Size | Sample Size | Acceptance Number |
| 2 to 90 | 13 | 1 |
| 91 to 150 | 20 | 2 |
| 151 to 280 | 32 | 3 |
| 281 to 500 | 50 | 5 |
| 501 to 1,200 | 80 | 7 |
| 1,201 to 3,200 | 125 | 10 |
| 3,201 to 10,000 | 200 | 14 |
| 10,001 ≥ | 315 | 21 |
