42CrMo Alloy Steel Grade 8 Black Oxide Hex Bolts
Product Overview
Grade 8 black oxide hex bolts are high-strength fasteners made from 42CrMo alloy steel and finished with a black oxide coating for improved corrosion resistance. Designed for heavy-duty applications, these bolts deliver exceptional tensile strength and durability in mechanical assemblies, construction, automotive, and industrial equipment.
Product Specification Table
| Parameter | Details |
|---|---|
| Product Name | Grade 8 Black Oxide Hex Bolt |
| Material | 42CrMo Alloy Steel |
| Standard | ANSI B18.2.1 / ISO 4014 |
| Grade | Grade 8 |
| Coating | Black Oxide |
| Thread Type | UNC/UNF/Metric |
| Sizes Available | M6–M30, 1/4″–1-1/4″ |
| Length Range | 10mm–300mm |
Technical Parameters
| Property | Value |
|---|---|
| Tensile Strength | ≥1200 MPa |
| Yield Strength | ≥1080 MPa |
| Hardness | 33–39 HRC |
| Proof Load | 85% of minimum tensile load |
| Operating Temperature | -40°C to 300°C |
Material & Manufacturing Process
The 42CrMo alloy steel used in Grade 8 black oxide hex bolts is known for its outstanding mechanical properties, including high tensile strength, excellent wear resistance, and good toughness. The manufacturing process includes:
Raw material inspection
Hot forging
Thread rolling
Heat treatment (quenching + tempering)
Black oxide coating
Dimensional inspection and packaging
This process ensures product consistency, precise threading, and superior surface finish.
Typical Applications & Industries
Grade 8 black oxide hex bolts are widely used in:
Heavy-duty automotive assemblies (e.g., engine and suspension systems)
Industrial machinery and press equipment
Construction and infrastructure (steel structures, beams)
Agricultural and mining equipment
Railway and transit systems
Performance Advantages of Grade 8 Hex Bolts
High Strength Alloy Steel Hex Bolts with Corrosion Resistance
Flybear Fastener manufactures its Grade 8 hex bolts using selected 42CrMo alloy steel to ensure outstanding load-bearing performance and mechanical durability.
Premium Material Selection: 42CrMo delivers high strength-to-weight ratio
Precision Manufacturing: Tight tolerances and clean threads ensure reliable fit
Advanced Surface Treatment: Black oxide finish provides mild corrosion resistance and anti-galling
Customizable Options: Available in various thread types, lengths, and head configurations
Stock Availability: Fast delivery supported by large inventory
Reliable After-Sales Support: Technical assistance available for project needs
Quality Inspection & Control
At Flybear Fastener, each batch of Grade 8 hex bolts undergoes a rigorous quality control process, including:
Tensile and hardness testing
Salt spray testing for surface treatment validation
Dimensional inspection using gauges and calipers
Batch traceability and certification compliance (ISO 898-1, IATF 16949)
Selection & Procurement Guide
When selecting Grade 8 black oxide hex bolts, consider the following:
Load requirements and stress conditions
Corrosion environment and coating needs
Thread fit (coarse/fine/metric)
Bolt length relative to grip length
We recommend contacting your technical team or suppliers for dimensional fit checks or ordering drawings. For high-volume or special requests, custom sizes and finishes are available.
Conclusion & Company Promotion
We always uphold the philosophy of “quality first, customer foremost,” and are committed to providing customers with high-quality fastener products and one-stop fastening solutions.
Explore more bolt varieties or contact us for tailored industry solutions and quotations.
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