ASME B18.2.1 / SAE J429 Grade 5 Hex Bolts | Inch Series, Quenched & Tempered

Product Introduction
Inch-series hexagon head bolts manufactured to ASME B18.2.1 for dimensions and SAE J429 Grade 5 for material and mechanical properties. The bolt has a standard hexagon head with washer face. Threads are UNC or UNF, Class 2A fit, per ASME B1.1. Diameters 1/4″ to 1-1/2″; lengths 1/2″ to 12″. Used in automotive, machinery, structural, and general industrial joints requiring higher strength than Grade 2 fasteners.

Material & Mechanical Properties
Medium carbon steel with minimum 0.28% carbon (range 0.28–0.55%), or carbon steel with additives such as boron (minimum manganese 0.60% when carbon is below 0.25%). Oil or water quenched and tempered at a minimum of 800°F (427°C).

• 1/4″–1″: proof load 85,000 psi; tensile strength 120,000 psi min; yield strength 92,000 psi min; elongation 14% min; reduction of area 35% min; core hardness C25–C34.

• 1-1/8″–1-1/2″: proof load 74,000 psi; tensile strength 105,000 psi min; yield strength 81,000 psi min; core hardness C19–C30.

Mechanical values are certified by lot. Mill test reports are available.

Geometry & Thread
Dimensions conform to ASME B18.2.1. Width across flats: 1/2″ = 7/8″; 5/8″ = 1-1/16″; 3/4″ = 1-1/4″; 7/8″ = 1-7/16″; 1″ = 1-5/8″; 1-1/4″ = 2″; 1-1/2″ = 2-3/8″. Head height ranges from 0.328″ for 1/2″ to 0.938″ for 1-1/2″. Thread length follows ASME B18.2.1 tables; for bolts over 6″, nominal thread length increases by 0.25″. UNC and UNF thread series per ASME B1.1, Class 2A.

Surface Finish
Plain (uncoated), electro-zinc plating with clear, yellow, or black passivation, zinc flake coatings (Dacromet/Geomet), and hot-dip galvanizing. Electro-zinc thickness is typically 5–12 μm. Hot-dip galvanizing to ASTM F2329 provides a minimum 50 μm coating; threads are tapped oversize before coating to maintain assembly fit.

Marking & Certification
Each bolt head carries a three-line radial “sunburst” grade marking evenly spaced on the head, identifying SAE J429 Grade 5. The manufacturer’s identification symbol is also applied. Compatible nuts include SAE J995 Grade 5 or ASTM A563 Grade A. Full lot traceability is maintained; inspection certificates and material test reports are available on request.

Application Suitability
Automotive chassis and engine assemblies, machinery frames, structural connections, and general industrial bolting where an inch-series, quenched and tempered hex bolt with Grade 5 strength is specified. The fastener is suitable for static and dynamic joints when installed to the applicable design torque and preload requirements.