Class 5.8
Grade 2
510 MPa
Minimum tensile · 74 ksi
- Material
- Low or medium carbon steel
- Application
- Light construction and general machinery
SAE J429 standard
Hex bolts
Grades 2, 5 and 8
A technical comparison to select the right strength level, heat treatment and marking for the demands of each application.
SAE J429
Highest strength in the series
150 ksi · 1034 MPa
Quick identification
Three grades for different levels of demand.
The number of radial lines on the head makes the grade of the bolt easy to recognise.
Class 8.8
Grade 5
827 MPa
Minimum tensile · 120 ksi
- Material
- Medium carbon steel, quenched and tempered
- Application
- Automotive industry, machinery and structures
Class 10.9
Grade 8
1034 MPa
Minimum tensile · 150 ksi
- Material
- Medium carbon alloy steel, quenched and tempered
- Application
- Heavy machinery and critical applications
Comparison sheet
SAE J429 technical specifications
Comparison adapted to every screen size.
SAE J429 Grade 2
- Material
- Low or medium carbon steel
- Heat treatment
- Not required
- Minimum tensile strength
- 74 ksi (510 MPa)
- Minimum yield strength
- 57 ksi (393 MPa)
- Proof load
- 55 ksi (379 MPa)
- Hardness
- HRB 70–100
- Head marking
- No radial lines, or 2 (manufacturer only)
- Typical applications
- Light construction, general machinery
- Coatings per the standard
- Black, zinc plated and galvanized
- Approximate ISO equivalent
- Class 5.8
SAE J429 Grade 5
- Material
- Medium carbon steel, quenched and tempered
- Heat treatment
- Quenched and tempered
- Minimum tensile strength
- 120 ksi (827 MPa)
- Minimum yield strength
- 92 ksi (634 MPa)
- Proof load
- 85 ksi (586 MPa)
- Hardness
- HRC 25–34
- Head marking
- 3 radial lines + manufacturer mark
- Typical applications
- Automotive, machinery and structures
- Coatings per the standard
- Black, zinc plated and galvanized*
- Approximate ISO equivalent
- Class 8.8
SAE J429 Grade 8
- Material
- Medium carbon alloy steel, quenched and tempered
- Heat treatment
- Quenched and tempered
- Minimum tensile strength
- 150 ksi (1034 MPa)
- Minimum yield strength
- 130 ksi (896 MPa)
- Proof load
- 120 ksi (827 MPa)
- Hardness
- HRC 33–39
- Head marking
- 6 radial lines + manufacturer mark
- Typical applications
- Heavy machinery and critical applications
- Coatings per the standard
- Black or coatings per ASTM F3393-24**
- Approximate ISO equivalent
- Class 10.9
Technical notes
Important considerations for surface treatment.
- 1Hot-dip galvanizing for Grade 5 must comply with the applicable standard and allow for thread overtapping.
- 2For Grade 8, non-electrolytic coatings are recommended to reduce the risk of hydrogen embrittlement (ASTM F3393-24).
Technical support
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