An independent hex cap screw reference & spec library Compare Grades FAQs
Home › SAE J429
Inch series · SAE

SAE J429

The inch-series standard that defines Grade 2, Grade 5, and Grade 8 — the grades identified by the radial lines on the head.

What it covers

SAE J429 sets the mechanical and material requirements for inch-series externally threaded fasteners in sizes up to 1-1/2″ inclusive. It's the specification behind the Grade 2, Grade 5, and Grade 8 hex cap screws most people picture — defining each grade's proof load, strength, ductility, hardness, and permitted chemistry.

Grade is identified directly on the head by a pattern of radial lines, which makes J429 fasteners the easiest to sort by eye. The summary below covers the three common grades; the standard also defines several others (Grades 1, 4, 5.1, 5.2, 8.1, and 8.2) not shown here.

Identification
Grade 2
No head markings
Grade 5
Three radial lines
Grade 8
Six radial lines
Mechanical properties
Source: published SAE J429 mechanical and chemical requirements. Verify against the current standard (or your IFI Fastener Standards book) before relying on these values for design.
GradeMarkingNominal Size Proof LoadYield, minTensile, min Elong, minCore HardnessTemper, min
Grade 2 1/4″ thru 3/4″ 55,000 psi57,000 psi74,000 psi 18%B80–B100—
Over 3/4″ thru 1-1/2″ 33,000 psi36,000 psi60,000 psi 18%B70–B100—
Grade 5 1/4″ thru 1″ 85,000 psi92,000 psi120,000 psi 14%C25–C34800°F
Over 1″ thru 1-1/2″ 74,000 psi81,000 psi105,000 psi 14%C19–C30800°F
Grade 8 1/4″ thru 1-1/2″ 120,000 psi130,000 psi150,000 psi 12%C33–C39800°F

Reduction of area: 35% min for all grades. Grade 2 values for 1/4″–3/4″ apply to bolts 6″ and shorter and to studs of all lengths; for bolts longer than 6″, Grade 1 requirements apply. Proof loads shown are full-size (tensile) values.

Chemical requirements
GradeMaterialCarbon Phosphorus, maxSulfur, maxMarking
Grade 2Low or medium carbon steel0.15–0.55%0.030%0.050%None
Grade 5Medium carbon steel, quenched & tempered0.28–0.55%0.030%0.050%3 radial lines
Grade 8Medium carbon alloy steel, quenched & tempered0.28–0.55%0.030%0.050%6 radial lines
Recommended mating nut

Grade 2, 5, and 8 hex cap screws are commonly assembled with SAE J995 nuts of the corresponding grade. Match or exceed the bolt grade so the nut isn't the weak point in the joint.

Alternate grades for larger diameters

SAE J429 tops out at 1-1/2″. For fasteners larger than that, these ASTM specifications are the usual substitutes — similar in strength but not identical, so confirm before swapping.

SAE J429 GradeASTM Equivalent
Grade 2ASTM A307 Grade A or B
Grade 5ASTM A449
Grade 8ASTM A354 Grade BD

Comparison applies to diameters through 1-1/2″; the specifications are similar but not identical.