Bolt Grade Markings and Strength Chart

Head Markings	Grade or Class	Material	Nominal Size Range (Inches)	Mechanical Properties
				Proof Load (psi)	Minimum Yield Strength (psi)	Minimum Tensile Strength (psi)
American Bolts
No Markings	Grade 2	Low or Medium Carbon Steel	1/4 thru 3/4	55,000	57,000	74,000
			Over 3/4 thru 1-1/2	33,000	36,000	60,000
3 Radial Lines	Grade 5	Medium Carbon Steel, Quenched and Tempered	1/4 thru 1	85,000	92,000	120,000
			Over 1 thru 1-1/2	74,000	81,000	105,000
6 Radial Lines	Grade 8	Medium Carbon Alloy Steel, Quenched and Tempered	1/4 thru 1-1/2	120,000	130,000	150,000

Bolt Grade Markings and Strength Chart Stainless markings vary. Most stainless is non-magnetic	18-8 Stainless	Steel alloy with 17-19% Chromium and 8-13% Nickel	1/4 thru 5/8		40,000 Min. 80,000 – 90,000 Typical	100,000 – 125,000 Typical
			3/4 thru 1		40,000 Min. 45,000 – 70,000 Typical	100,000 Typical
			Above 1		40,000 Min. 45,000 – 70,000 Typical	80,000 – 90,000 Typical
Metric Bolts
8.8	Class 8.8	Medium Carbon Steel, Quenched and Tempered	All Sizes thru 1-1/2	85,000	92,000	120,000
10.9	Class 10.9	Alloy Steel, Quenched and Tempered	All Sizes thru 1-1/2	120,000	130,000	150,000
Stainless markings vary. Most stainless is non-magnetic	A-2 Stainless	Steel alloy with 17-19% Chromium and 8-13% Nickel	1/4 thru 5/8		40,000 Min. 80,000 – 90,000 Typical	100,000 – 125,000 Typical
			3/4 thru 1		40,000 Min. 45,000 – 70,000 Typical	100,000 Typical
			Above 1		40,000 Min. 45,000 – 70,000 Typical	80,000 – 90,000 Typical
Tensile Strength: The maximum load in tension (pulling apart) which a material can withstand before breaking or fracturing. Yield Strength: The maximum load at which a material exhibits a specific permanent deformation Proof Load: An axial tensile load which the product must withstand without evidence of any permanent set.