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US Grade Bolt Markings – Strength Requirements |
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Head Grade Marking |
Specification |
Material |
Nominal Size (Inches) |
Proof Load psi |
Tensile Strength Min psi |
Yield Strength Min psi |
Rockwell Hardness (Min/Max) |
 |
Grade 1 – SAE J429 Bolts, Screws and Studs |
Low or medium carbon steel |
1/4″ – 1- 1/2″ |
33,000 |
60,000 |
36,000 |
B70 / B100 |
 |
Grade 2 – SAE J429 Bolts, Screws and Studs |
Low or medium carbon steel |
1/4″ – 3/4″ >3/4″ – 1- 1/2″ |
55,000 33,000 |
74,000 60,000 |
57,000 36,000 |
B80 / B100 B70 / B100 |
 |
Grade 5 – SAE J429 Bolts, Screws and Studs |
Medium carbon steel or carbon steel with additives, quenched and tempered |
1/4″ – 1″ >1″ – 1- 1/2″ |
85,000 74,000 |
120,000 105,000 |
92,000 81,000 |
C25 / C34 / C19 / C30 |
 |
Grade 5.1 – SAE J429 Sems |
Low or medium carbon steel, quenched and tempered |
No. 4 – 5/8″ |
85,000 |
120,000 |
92,000 |
C25 / C40 |
 |
Grade 5.2 – SAE J429 Bolts, Screws and Studs |
Low carbon Boron steel, quenched and tempered |
1/4″ – 1″ |
85,000 |
120,000 |
92,000 |
C26 / C36 |
 |
Grade 8 – SAE J429 Bolts and Screws |
Medium carbon / alloy steel with additives, quenched and tempered |
1/4″ – 1- 1/2″ |
120,000 |
150,000 |
130,000 |
C33 / C39 |
 |
Grade 8.2 – SAE J429 Bolts and Screws |
Low carbon Boron steel, quenched and tempered |
1/4″ – 1″ |
120,000 |
150,000 |
130,000 |
C33 / C39 |
 |
L9 – Grade 9 Bolts, Nuts and Washers |
Hight strength alloy steel |
1/4″ – 1- 1/2″ |
145,000 |
180,000 |
155,000 |
C38 / C42 |
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ASTM A307 Grade A Bolts, Screws and Studs (General Engineering) |
Low or medium carbon steel |
1/4″ – 4″ |
33,000 |
60,000 |
36,000 |
B69 / B100 |
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ASTM A307 Grade B Bolts, Screws and Studs (Flanged Joints) |
Low or medium carbon steel |
1/4″ – 4″ |
33,000 |
60,000 |
36,000 |
B69 / B95 |
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One End Green |
ASTM A307 Grade C |
Low or medium carbon steel |
1/2″ – 4″ |
– |
58 min 80 max |
36,000 |
– |
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Head Grade Marking |
Specification |
Material |
Nominal Size (Inches) |
Proof Load psi |
Tensile Strength Min psi |
Yield Strength Min psi |
Rockwell Hardness (Min/Max) |
|
One End Blue |
ASTM F1554 Grade 36 |
Low or medium carbon steel |
1/2″ – 4″ |
– |
58 min 80 max |
36,000 |
– |
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One End Yellow |
ASTM F1554 Grade 55 |
Low or medium carbon steel |
1/2″ – 2″ 2-1/4″ – 2-1/2″ 3-3/4″ – 3″ 3-1/4″ – 4″ |
– |
75 min 95 max |
55,000 |
– |
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ASTM A325 Type 1 High strength structural bolts |
Medium carbon steel, quenched and tempered |
1/2″ – 1″ 1-1/8″ – 1- 1/2″ |
85,000 74,000 |
120,000 105,000 |
92,000 81,000 |
C24 / C35 / C19 / C31 |
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ASTM A325 Type 2 High strength structural bolts |
Low carbon Martensitic steel, quenched and tempered |
1/2″ – 1″ 1-1/8″ – 1- 1/2″ |
85,000 74,000 |
120,000 105,000 |
92,000 81,000 |
C24 / C35 / C19 / C31 |
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ASTM A325 Type 3 High strength structural bolts |
Atmospheric corrosion-resistant steel, quenched and tempered |
1/2″ – 1″ 1-1/8″ – 1- 1/2″ |
85,000 74,000 |
120,000 105,000 |
92,000 81,000 |
C24 / C35 / C19 / C31 |
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ASTM A354 Grade BB Bolts and studs |
Alloy steel, quenched and tempered |
1/4″ – 2- 1/2″ > 2-1/2″ – 4″ |
80,000 75,000 |
105,000 100,000 |
83,000 78,000 |
C26 / C36 / C22 / C33 |
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ASTM A354 Grade BC Bolts and studs |
Alloy steel, quenched and tempered |
1/4″ – 2- 1/2″ > 2-1/2″ – 4″ |
105,000 95,000 |
125,000 115,000 |
109,000 99,000 |
C26 / C36 / C22 / C33 |
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One End Red |
ASTM F1554 Grade 105 |
Medium carbon steel, Alloy Steel Q & T |
1/2″ – 3″ |
– |
128 min 150 max |
105,000 |
– |
 |
ASTM A354 Grade BD Bolts, screws and studs |
Alloy steel, quenched and tempered |
1/4″ – 2- 1/2″ > 2-1/2″ – 4″ |
120,000 105,000 |
150,000 140,000 |
130,000 120,000 |
C33 / C39 / C31 / C39 |
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ASTM A449 Type 1 Bolts, screws and studs |
Medium carbon steel, quenched and tempered |
1/4″ – 1″ >1 – 1-1/2″ |
85,000 74,000 |
120,000 105,000 |
92,000 |
C25 / C34 |
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81,000 |
C25 / C34 |
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ASTM A449 Type 2 Bolts, screws and studs |
Low carbon Martensitic steel, quenched and tempered |
1/4″ – 1″ |
85,000 |
120,000 |
58,000 |
C25 / C34 |
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Head Grade Marking |
Specification |
Material |
Nominal Size (Inches) |
Proof Load psi |
Tensile Strength Min psi |
Yield Strength Min psi |
Rockwell Hardness (Min/Max) |
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ASTM A490 Type 1 High strength structural bolts |
Medium carbon alloy steel, quenched and tempered |
1/2″ – 1- 1/2″ |
120,000 |
150,000 min 170,000 max |
130,000 |
C33 / C38 |
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ASTM A490 Type 2 High strength structural bolts |
Low carbon Martensitic steel, quenched and tempered |
1/2″ – 1″ |
120,000 |
150,000 min 170,000 max |
130,000 |
C33 / C38 |
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ASTM A490 Type 3 High strength structural bolts |
Atmospheric corrosion-resistant steel, quenched and tempered |
1/2″ – 1- 1/2″ |
120,000 |
150,000 min 170,000 max |
130,000 |
C33 / C38 |
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Metric Bolts |
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Head Grade Marking |
Specification |
Material |
Proof Load (Min) |
Tensile Strength min (MPa) |
Yield Strength Min (MPa) |
Hardness Min/Max |
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Class 4.6 |
Low or medium carbon steel |
220 |
400 (58,000 psi) |
240 |
HRB-67 / HRB-95 |
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Class 5.8 |
Low or medium carbon steel, quenched and tempered |
380 |
520 (75,000 psi) |
420 |
HRB-82 / HRB-95 |
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Class 8.8 |
Medium carbon steel, quenched and tempered |
600 |
830 (120,000 psi) |
640 |
HRC-22 / HRC-34 |
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Class 10.9 |
Alloy steel, quenched and tempered |
830 |
1040 (150,000 psi) |
940 |
HRC-32 / HRC-39 |
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Class 12.9 |
Alloy steel, quenched and tempered |
970 |
1220 (176,000 psi) |
1220 |
HRC-39 / HRC-44 |
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Usually stamped A-2 or A-4 |
A2 & A4 Stainless |
Steel alloy with chromium and nickel |
N/A |
500 Min 700 Typical |
210 Min 450 Typical |
N/A |
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Note: Manufacturer’s identification mark are also stamped when applicable
Tensile Strength: The maximum load in tension (pull apart) which a material can withstand before breaking or fracturing.
Yield Strength: The stress at which a specific amount of permanent deformation is produced
Proof Load: An axial tensile load which the product must withstand without evidence of any permanent set.
