Click here - Printable Metric Bolt Grade Chart (PDF)
Printable Chart for easy comparison between Metric Bolt Classes and US grades equivalents.
Head Markings |
Metric Bolt Class |
Mechanical Properties |
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Proof Load (MPa) |
Min Yield (MPa) |
Min Tensile Strength (MPa) |
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- Class 12.9 - Alloy Steel, quenched and tempered |
970 |
1,100 |
1,220 |
 |
- Class 10.9 - Alloy Steel, quenched and tempered |
830 |
940 |
1,040 |
 |
- Class 8.8 - Medium carbon steel, quenched and tempered |
580-600 |
640-660 |
800-830 |
 |
A4-80 Stainless Similar to 316, commonly used in Marine environments |
N/A | 600 | 800 |
 |
A2-70 Stainless Most common stainless. Similar to 304 / 18-8 |
N/A |
450 |
700 |
|
US/Imperial LBF/In²(PSI) |
Metric Mpa(N/mm²) |
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Chart for easy comparison of US / Metric screws and bolts. It is always a bit unusual to compare them as they use different measurement systems (PSI vs. Mpa). |
180,000 SAE Grade 8- 150,000 SAE Grade 5 - 120,000 116,000 101,530 75,420 SAE Grade 2 - 74,000 58,020 |
1,220 - Class 12.9 1,040 - Class 10.9 830 - Class 8.8 800 - Stainless A4-80 700 - Stainless A2-70 520 - Class 5.8 510 400 - Class 4.6 |
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Proof Load: An axial tensile load which the product must withstand without evidence of any permanent set.
Yield Strength: The maximum load at which a material exhibits a specific permanent deformation
1MPa = 1N/mm2 = 145 pounds/inch2
Tensile Strength: The maximum load in tension (pulling apart) which a material can withstand before breaking or fracturing.
2 comments
Anthony Nastus
Need a bolt that is not brittle and can with stand lateral pressures. Tensile strength not as important. Have an 8.8 JH that is braking from side to side movement.
Ravikumar Kanagaraj
hi Team,
I am looking for A4-70 and A4-80 M8 bolts for the project. Here there is no proof load is mentioned. What is the applicable tightening torque for these bolts and how it is being calculated, Please share the details