ASTM A307 Grade A and B Bolts (60 ksi)
The general-purpose carbon steel bolt: 60 ksi tensile, not heat treated, weldable and galvanizable — Grade A for general use, Grade B for flanged pipe joints with a 100 ksi cap.
What A307 A / B is.
ASTM A307 covers low-carbon steel bolts, studs and threaded rod at 60 ksi minimum tensile with no heat treatment. Grade A is the general-purpose bolt; Grade B, with a 60 to 100 ksi tensile band and a hardness cap, is for flanged joints in piping systems with cast-iron flanges, where a bolt that is too strong could crack the flange. It is the ASTM counterpart of SAE J429 Grade 2 and of ASME B18 machine bolts.
We machine A307 hex and heavy hex bolts, studs and threaded rod from certified low-carbon bar and supply them plain, zinc plated or hot-dip galvanized with A563 Grade A nuts.
Chemical composition.
| Element | Symbol | Min % | Max % |
|---|---|---|---|
| Carbon | C | — | 0.29 |
| Manganese | Mn | — | 1.20 |
| Phosphorus | P | — | 0.04 |
| Sulfur, Grade A | S | — | 0.15 |
| Sulfur, Grade B | S | — | 0.05 |
Values per ASTM A307-14 Table 1 (verified against the specification). Confirm the edition called out on your purchase order with our estimating team. Grade A permits resulfurized steel to 0.15 % S; Grade B is limited to 0.05 % S.
Mechanical properties.
| Grade / condition and size | Tensile strength, min (ksi) | Yield or proof, min (ksi) | Elongation, min (%) | Reduction of area, min (%) | Hardness |
|---|---|---|---|---|---|
| Grade A — all sizes | 60 | — | 18 | — | 69–100 HRB (121–241 HBW) |
| Grade B — all sizes | 60 (100 max) | — | 18 | — | 69–95 HRB (121–212 HBW) |
Values per ASTM A307-14 Tables 2 and 4 (verified against the specification). Confirm the edition called out on your purchase order with our estimating team. Full-size tensile loads by thread size are in Table 3 of the specification.
Specifications that apply.
How A307 A / B ships from Houston.
- Hex and heavy hex bolts and cap screws
- Studs and threaded rod
- Nuts and washers to match
- Machined specials to drawing
A307 A / B fasteners we make.
Every item is manufactured to your drawing or standard in A307 A / B, imperial or metric, with an EN 10204 3.1 certificate.
What is an A307 bolt?
A307 is the specification behind most plain carbon steel bolts and threaded rod. The steel is low carbon, the bolt is not heat treated, and the only strength requirement is 60 ksi minimum tensile, so the product is inexpensive, ductile, weldable and easy to galvanize. Grade B adds a maximum tensile of 100 ksi and a lower hardness cap because it is meant for cast-iron pipe flanges, where an over-strong bolt can break the flange before the bolt yields.
Testing, certification and marking
- Tensile, proof load and hardness tested per lot to ASTM F606
- Grade mark 307A or 307B and manufacturer's identification on the head or one end
- Certificate of conformance or test report with heat number on request; EN 10204 3.1 available
- Coating thickness reported when plated or galvanized
SAE Grade 5 / ASTM A449 Bolts (120 ksi)
The everyday high-strength bolt: quenched and tempered medium-carbon steel at 120 ksi to 1 in., stepping down for larger sizes — Grade 5 in SAE terms, A449 in ASTM terms.
ASTM F1554ASTM F1554 Grades 36, 55 and 105 Anchor Bolts
The anchor-bolt specification: Grade 36 carbon steel, Grade 55 weldable higher strength, and Grade 105 quenched-and-tempered alloy — straight, bent or headed, plain or galvanized, ½ to 4 in. (Grade 105 to 3 in.)
ASTM A108 cold-finished bar · chemistry per ASTM A29 / SAE J4031018 Carbon Steel (UNS G10180)
The everyday machining steel: low carbon, easily welded and case hardened, cold drawn for a clean finish — for pins, spacers, brackets and non-critical machined parts.