ASTM A307

Covers — carbon-steel bolts, studs, and threaded rod of nominal 60 ksi tensile strength: Grade A (general), Grade B (cast-iron flanged joints), and Grade C (nonheaded anchor bolts, structural).

Does NOT cover (exclusions) — the following are governed elsewhere:

• High-pressure/high-temperature pressure-boundary bolting → ASTM A193 / A320.
• Structural high-strength bolts → ASTM F3125 (A325/A490).
• Nut requirements → ASTM A563 / A194.

A307 is general/structural bolting; do not use it on rated pressure-boundary flanged joints.

A307 sets minimum requirements for general bolting:

• Grades — A (general), B (cast-iron flanges, capped strength), C (anchor bolts to A36-type).
• Mechanical Properties — 60 ksi minimum tensile; Grade B has a maximum tensile to protect cast-iron flanges.
• Dimensions & Marking — head/thread per B18.2.1 and grade/manufacturer marking.

ASTM A307 covers low-strength (60 ksi) carbon-steel bolts, studs, and threaded rod for general and structural use. Grade A is the general-purpose choice, Grade B is made specifically for cast-iron flanged joints (its capped strength avoids cracking brittle flanges), and Grade C serves as structural anchor bolts.

It is not a pressure-boundary bolting material — rated high-temperature/high-pressure flanged joints require A193 or A320. Using A307 where the flange rating calls for A193 dangerously under-specifies the joint.

Engineering Note: Grade B's maximum-strength cap is a feature, not a defect — it protects cast-iron flanges from being over-torqued; do not "upgrade" to a stronger bolt on those joints.