Steel Fasteners by Grade
This comprehensive reference covers mechanical properties for all common fastener materials. Use this guide to compare strengths and select the right material for your application.
Steel Fasteners by Grade
SAE (Inch) Bolt Grades
| Grade | Material | Tensile Strength | Yield Strength | Proof Load | Hardness |
|---|---|---|---|---|---|
| Grade 2 | Low/Medium Carbon | 74,000 psi (510 MPa) | 57,000 psi (393 MPa) | 55,000 psi (379 MPa) | Rockwell B70-100 |
| Grade 5 | Medium Carbon, Q&T | 120,000 psi (827 MPa) | 92,000 psi (634 MPa) | 85,000 psi (586 MPa) | Rockwell C25-34 |
| Grade 8 | Medium Carbon Alloy, Q&T | 150,000 psi (1,034 MPa) | 130,000 psi (896 MPa) | 120,000 psi (827 MPa) | Rockwell C33-39 |
| Grade 8.2 | Low Carbon Martensite | 150,000 psi (1,034 MPa) | 130,000 psi (896 MPa) | 120,000 psi (827 MPa) | Rockwell C33-39 |
Q&T = Quenched and Tempered
Metric (ISO) Bolt Property Classes
| Class | Material | Tensile Strength | Yield Strength | Proof Load | Hardness |
|---|---|---|---|---|---|
| 4.6 | Low/Medium Carbon | 400 MPa (58,000 psi) | 240 MPa (34,800 psi) | 225 MPa (32,600 psi) | Rockwell B67-95 |
| 5.8 | Low/Medium Carbon | 520 MPa (75,400 psi) | 415 MPa (60,200 psi) | 380 MPa (55,100 psi) | Rockwell B82-95 |
| 8.8 | Medium Carbon, Q&T | 800 MPa (116,000 psi) | 640 MPa (92,800 psi) | 580 MPa (84,100 psi) | Rockwell C22-32 |
| 10.9 | Medium Carbon Alloy, Q&T | 1,040 MPa (150,800 psi) | 940 MPa (136,300 psi) | 830 MPa (120,400 psi) | Rockwell C32-39 |
| 12.9 | Alloy Steel, Q&T | 1,220 MPa (177,000 psi) | 1,100 MPa (159,500 psi) | 970 MPa (140,700 psi) | Rockwell C39-44 |
Understanding Metric Class Numbers:
- First digit × 100 = Tensile strength in MPa (e.g., 8 × 100 = 800 MPa)
- First digit × second digit × 10 = Yield strength in MPa (e.g., 8 × 8 × 10 = 640 MPa)
Grade Equivalency Reference
| SAE Grade | Metric Class | Relative Strength |
|---|---|---|
| Grade 2 | Class 5.8 | Low strength |
| Grade 5 | Class 8.8 | Medium strength |
| Grade 8 | Class 10.9 | High strength |
| — | Class 12.9 | Very high strength |
Stainless Steel Fasteners
Austenitic (300 Series)
| Designation | Material | Tensile Strength | Yield Strength (0.2%) | Proof Load | Hardness |
|---|---|---|---|---|---|
| A2-50 | 304/18-8 (soft) | 500 MPa (72,500 psi) | 210 MPa (30,500 psi) | 310 MPa (45,000 psi) | Rockwell B70 max |
| A2-70 | 304/18-8 (cold worked) | 700 MPa (101,500 psi) | 450 MPa (65,300 psi) | 500 MPa (72,500 psi) | Rockwell B80-95 |
| A2-80 | 304/18-8 (strain hardened) | 800 MPa (116,000 psi) | 600 MPa (87,000 psi) | 640 MPa (92,800 psi) | Rockwell B90-100 |
| A4-50 | 316 (soft) | 500 MPa (72,500 psi) | 210 MPa (30,500 psi) | 310 MPa (45,000 psi) | Rockwell B70 max |
| A4-70 | 316 (cold worked) | 700 MPa (101,500 psi) | 450 MPa (65,300 psi) | 500 MPa (72,500 psi) | Rockwell B80-95 |
| A4-80 | 316 (strain hardened) | 800 MPa (116,000 psi) | 600 MPa (87,000 psi) | 640 MPa (92,800 psi) | Rockwell B90-100 |
Note: "A2" = 300 series austenitic (typically 304), "A4" = molybdenum-bearing austenitic (typically 316)
Martensitic (400 Series)
| Grade | Condition | Tensile Strength | Yield Strength | Hardness |
|---|---|---|---|---|
| 410 | Annealed | 450 MPa (65,000 psi) | 275 MPa (40,000 psi) | Rockwell B80-90 |
| 410 | Hardened (H) | 965 MPa (140,000 psi) | 760 MPa (110,000 psi) | Rockwell C35-40 |
| 410 | Hardened (HT) | 1,100 MPa (160,000 psi) | 860 MPa (125,000 psi) | Rockwell C38-45 |
| 416 | Hardened | 760 MPa (110,000 psi) | 585 MPa (85,000 psi) | Rockwell C30-40 |
Precipitation Hardening
| Grade | Condition | Tensile Strength | Yield Strength | Hardness |
|---|---|---|---|---|
| 17-4 PH (630) | H1150 | 930 MPa (135,000 psi) | 725 MPa (105,000 psi) | Rockwell C28-35 |
| 17-4 PH (630) | H1025 | 1,070 MPa (155,000 psi) | 1,000 MPa (145,000 psi) | Rockwell C35-40 |
| 17-4 PH (630) | H900 | 1,310 MPa (190,000 psi) | 1,170 MPa (170,000 psi) | Rockwell C40-47 |
Shear Strength Reference
Shear strength is typically not directly specified but can be estimated:
| Material | Shear Strength (approximate) |
|---|---|
| Grade 2 | 44,000 psi (303 MPa) — ~60% of tensile |
| Grade 5 | 72,000 psi (496 MPa) — ~60% of tensile |
| Grade 8 | 90,000 psi (620 MPa) — ~60% of tensile |
| 304 Stainless (A2-70) | 56,000 psi (386 MPa) — ~55% of tensile |
| 316 Stainless (A4-70) | 56,000 psi (386 MPa) — ~55% of tensile |
| 17-4 PH (H1025) | 85,000 psi (586 MPa) — ~55% of tensile |
General Rule: Shear strength ≈ 55-60% of tensile strength for steel fasteners.
Temperature Limits
Steel Fasteners
| Grade | Min Temp | Max Continuous | Max Intermittent |
|---|---|---|---|
| Grade 2 | -40°F (-40°C) | 450°F (230°C) | 500°F (260°C) |
| Grade 5 | -40°F (-40°C) | 450°F (230°C) | 500°F (260°C) |
| Grade 8 | -40°F (-40°C) | 450°F (230°C) | 500°F (260°C) |
| Class 10.9 | -40°F (-40°C) | 480°F (250°C) | 550°F (290°C) |
| Class 12.9 | -40°F (-40°C) | 480°F (250°C) | 550°F (290°C) |
Note: Above 500°F (260°C), tempered steel begins to lose hardness. Use high-temp alloys (A286, Inconel) for elevated temperature applications.
Stainless Steel Fasteners
| Grade | Min Temp | Max Continuous | Notes |
|---|---|---|---|
| 304 (A2) | -425°F (-254°C) | 800°F (427°C) | Sensitization above 800°F |
| 316 (A4) | -425°F (-254°C) | 800°F (427°C) | Better high-temp performance |
| 410 | -40°F (-40°C) | 1,200°F (650°C) | Loses corrosion resistance |
| 17-4 PH | -100°F (-73°C) | 600°F (316°C) | Age hardening can change |
Note: 300 series stainless excels in cryogenic applications. 400 series offers better high-temp strength but less corrosion resistance.
Non-Ferrous Fasteners
Brass
| Alloy | Tensile Strength | Yield Strength | Hardness |
|---|---|---|---|
| C36000 (Free Cutting) | 49,000 psi (338 MPa) | 18,000 psi (124 MPa) | Rockwell B60 |
| C46400 (Naval Brass) | 54,000 psi (372 MPa) | 25,000 psi (172 MPa) | Rockwell B65 |
| Silicon Bronze | 70,000 psi (483 MPa) | 38,000 psi (262 MPa) | Rockwell B80 |
Aluminum
| Alloy | Temper | Tensile Strength | Yield Strength | Hardness |
|---|---|---|---|---|
| 2024 | T4 | 62,000 psi (427 MPa) | 40,000 psi (276 MPa) | Brinell 120 |
| 6061 | T6 | 45,000 psi (310 MPa) | 40,000 psi (276 MPa) | Brinell 95 |
| 7075 | T6 | 83,000 psi (572 MPa) | 73,000 psi (503 MPa) | Brinell 150 |
Titanium
| Alloy | Tensile Strength | Yield Strength | Hardness |
|---|---|---|---|
| Grade 2 (CP) | 50,000 psi (345 MPa) | 40,000 psi (276 MPa) | Rockwell C10-15 |
| Grade 5 (Ti-6Al-4V) | 130,000 psi (896 MPa) | 120,000 psi (827 MPa) | Rockwell C30-36 |
Comparative Strength Overview
By Ultimate Tensile Strength (Ranked)
| Rank | Material | Tensile Strength |
|---|---|---|
| 1 | 17-4 PH H900 | 190,000 psi (1,310 MPa) |
| 2 | Class 12.9 | 177,000 psi (1,220 MPa) |
| 3 | 410 SS (Hardened) | 160,000 psi (1,100 MPa) |
| 4 | 17-4 PH H1025 | 155,000 psi (1,070 MPa) |
| 5 | Grade 8 / Class 10.9 | 150,000 psi (1,034 MPa) |
| 6 | Ti-6Al-4V | 130,000 psi (896 MPa) |
| 7 | Grade 5 / Class 8.8 | 120,000 psi (827 MPa) |
| 8 | A2-80 / A4-80 | 116,000 psi (800 MPa) |
| 9 | A2-70 / A4-70 | 101,500 psi (700 MPa) |
| 10 | 7075-T6 Aluminum | 83,000 psi (572 MPa) |
| 11 | Grade 2 | 74,000 psi (510 MPa) |
| 12 | Silicon Bronze | 70,000 psi (483 MPa) |
| 13 | 6061-T6 Aluminum | 45,000 psi (310 MPa) |
| 14 | Brass | 49,000 psi (338 MPa) |
Hardness Conversion Reference
| Rockwell C | Rockwell B | Brinell (HB) | Approximate Tensile (psi) |
|---|---|---|---|
| — | 70 | 130 | 67,000 |
| — | 80 | 150 | 79,000 |
| — | 90 | 175 | 93,000 |
| — | 100 | 212 | 112,000 |
| 20 | — | 226 | 119,000 |
| 25 | — | 253 | 133,000 |
| 30 | — | 286 | 150,000 |
| 35 | — | 327 | 171,000 |
| 40 | — | 371 | 195,000 |
| 45 | — | 421 | 220,000 |
Key Takeaways
1. Grade 5 / Class 8.8 — The standard for most structural applications
2. Grade 8 / Class 10.9 — Use when higher strength is required; specify careful torque control
3. 18-8 / A2-70 — Standard stainless; similar strength to Grade 2 but corrosion resistant
4. 316 / A4-70 — Same strength as 304 but better corrosion resistance
5. 17-4 PH — When you need high strength AND corrosion resistance
6. Shear strength — Roughly 60% of tensile; design for this in shear applications
7. Temperature matters — Above 500°F, standard steel loses strength; use appropriate alloys
Design Factor: Always apply a safety factor of 2-4x depending on application criticality. Published strengths are minimums under controlled conditions.