Bolt Grade Markings and Properties
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Identification Markings
(Fasteners may also have manufacturer
I.D. markings) |
Specification |
Material |
Nominal Size Range (inches) |
Mechanical Properties |
|
Proof Load (psi) |
Minimum Yield Strength (psi) |
Minimum Tensile Strength (psi) |
|
U.S. |
|
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 |
|
Stainless markings
vary. most stainless steel is non-magnetic |
18.8 Stainless
and
A-2 Metric |
Steel alloy with 17-19% Chromium and
8-13% Nickel |
1/4 thru 5/8 |
|
80,000 – 90,000 |
100,000 – 125,000 |
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3/4 thru 1 |
|
45,000 – 70,000 |
100,000 |
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Above 1 |
|
80,000 – 90,000 |
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Metric |
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8.8 |
Class 8.8 |
Medium Carbon Steel, Quenched and
Tempered |
All Sizes thru 1-1/2 |
85,000 |
92,000 |
120,000 |
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10.9
|
Class 10.9 |
Alloy Steel, Quenched and Tempered |
All Sizes thru 1-1/2 |
120,000 |
130,000 |
150,000 |
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Tensile Strength: The
maximum load in tension (pulling apart or shearing 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 |
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