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Bolt Grades and Head Markings

Bolt Grades and Head Markings

Grade Radial Bolt Markings Material Nominal Size Diameter/Inches Proof Load
psi
Tensile Strength
minimum psi
Yield Strength
minimum psi
Grade 2

No Radial Lines
Grade 2 Bolt - No Radial Lines Low or Medium Carbon Steel 1/4" to 3/4" 55,000 74,000 57,000
Over 3/4" thru 1 1/2" 33,000 60,000 36,000
Grade 5

3 Radial Lines
Grade 5 Bolt - 3 Radial Lines Medium Carbon Steel 1/4" to 1" 85,000 120,000 92,000
Over 1" thru 1 1/2" 74,000 105,000 81,000
Grade 8

6 Radial Lines
Grade 8 Bolt - 5 Radial Lines Medium Carbon Alloy Steel 1/4" thru 1 1/2" 120,000 150,000 130,000
Metric 8.8 Metric Bolt - Grade 8.8 Medium Carbon Steel All sizes under 16mm 580 800 640
16mm thru 72mm 600 830 660
Metric 10.9 Metric Bolt - Grade 10.9 Alloy Steel 5mm thru 100mm 830 1040 940

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