High Strength Bolt Grades 8.8 / 10.9 / 12.9: Compl. Guia completo de High Strength Bolt Grades 8.8 / 10.9 / 12.9: Compl - especificações, aplicações e seleção de fornecedores para exportação B2B para mercados africanos.
Understanding the Grade Marking System
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Grade 8.8: Galvanized Bolts for Machinery and Auto Chassis
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Grade 10.9: Structural Bolts for Construction and Engineering
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Grade 12.9: Black Oxide Socket Bolts for Precision Machinery
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Grade 8.8 vs 10.9 vs 12.9: Mechanical Properties Comparison
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| Property | Grade 8.8 | Grade 10.9 | Grade 12.9 |
|---|---|---|---|
| Tensile Strength | 800 MPa | 1000 MPa | 1220 MPa |
| Yield Strength | 640 MPa | 900 MPa | 1100 MPa |
| Proof Load | 580 MPa | 830 MPa | 1100 MPa |
| Head Marking | 8.8 | 10.9 | 12.9 |
| Common Coatings | HDG, Zinc Plated | Zinc Plated, HDG | Black Oxide, Parkerized |
| Auto Chassis | Yes (standard) | Yes (heavy duty) | Rarely |
| Structural Steel | Yes (indoor) | Yes (preferred) | Specialized |
| Machinery/Precision | General | Heavy duty | High precision |
| Price Index | 1.0x (baseline) | 1.3x | 1.8x |
Frequently Asked Questions
See frequently asked questions below.
Can I substitute a 10.9 bolt where 8.8 is specified?
Generally yes—using a higher grade bolt where lower is specified is usually acceptable. However, always verify torque specifications match, and consider thread engagement depth.
What coating should I use for outdoor high-strength bolts?
Hot-dip galvanizing (HDG) is recommended for outdoor structural bolts. The zinc coating provides cathodic protection. Note: HDG reduces thread class from 6g to 8g.
What is the difference between hex bolts and socket head cap screws?
Hex bolts use an external hex drive requiring a wrench. Socket head cap screws use an internal hex (Allen) drive, allowing lower profile installation in recessed areas.
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