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Bolt Grade Markings and Strength Chart
| Head Marking |
Grade and
Material |
Nominal Size Range
(inches) |
Mechanical Properties |
Proof Load
(psi) |
Min. Yield Strength
(psi) |
Min. Tensile Strength
(psi) |
|
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 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 |
|
80,000 – 90,000 Typical |
| Head Marking |
Class and
Material |
Nominal Size Range
(mm) |
Mechanical Properties |
Proof Load
(MPa) |
Min. Yield Strength
(MPa) |
Min. Tensile Strength
(MPa) |
|
8.8 |
Class 8.8
Medium
Carbon Steel, Quenched and Tempered |
All Sizes below 16mm |
580 |
640 |
800 |
| 16mm - 72mm |
600 |
660 |
830 |
10.9 |
Class 10.9
Alloy
Steel, Quenched and Tempered |
5mm - 100mm |
830 |
940 |
1040 |
12.9 |
Class 12.9
Alloy
Steel, Quenched and Tempered |
1.6mm - 100mm |
970 |
1100 |
1220 |
Stainless markings vary. Most stainless
is non-magnetic.
Usualy stamped A-2 |
A-2 Stainless
Steel alloy with 17- 19% Chromium and
8-13% Nickel |
All Sizes thru 20mm |
|
210 Min.
450 Typical
|
500 Min.
700 Typical
|
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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.
1MPa = 1N/mm2 = 0.2248 pounds/mm2
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