Metric Bolt Grade Markings and Steel Strength Chart - MonsterBolts
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 |
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A2-70 Stainless Most common stainless. Similar to 304 / 18-8 |
N/A |
450 |
700 |
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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.