BOLT MARKINGS AND STRENGTH (US)

Head MarkingGrade & MaterialSize Range (inches)Mechanical Properties
Proof Load (psi)
Mechanical Properties
Min. Yield Strength (psi)
Mechanical Properties
Min Tensile (psi)
gr2_Marking

No Markings
Grade 2
Low or Medium
Carbon Steel
1/4" - 3/4"

Above 3/4"-1 1/2"
55,000

33,000
57,000

36,000
74,000

60,000
gr5_Marking

3 Radial Lines
Grade 5
Medium Carbon
Steel
1/4"-1"

Above 1" -
1 1/2
85,000

74,000
92,000

81,000
120,000

105,000
gr8_Marking

6 Radial Lines
Grade 8
Medium Carbon
Steel
1/4"-1 1/2"120,000130,000150,000
Stainless Steel
Markings Vary
18-8 Stainless
Steel Alloy with
17-19% Chromium &
8-13% Nickel
Up to 1"-20,000 Min.
65,000 Typical
65,000 Min.
100,000-150,000
Typical