5/16"-24 L9 Hex Head Cap Screw – Fine Thread Alloy Steel Zinc Yellow CR+3 (Made in U.S.A.)

5/16"-24 L9 Hex Head Cap Screw – Fine Thread Alloy Steel Zinc Yellow CR+3 (Made in U.S.A.)

Part Numbers: 440128, 440132, 440136, 440138, 440140, 440142, 440144, 440148, 440152

Discover the strength and reliability of our 5/16"-24 L9 Hex Head Cap Screws, engineered to provide high performance in the most demanding applications. These USA-made fasteners are crafted from premium alloy steel, ensuring industry-leading durability. With an impressive tensile strength of 180,000 PSI, these bolts are specifically designed for high-stress environments where dependable fastening is critical.

Why Choose L9 Hex Head Cap Screws?

L9 fasteners set the standard in high-performance SAE grading, ideal for applications requiring top-tier strength and longevity. Marked by nine radial lines and an "L9" stamp, these hex cap screws are recognized for their superior quality. The fine thread (UNF) design provides a tighter fit and improved clamp load, ideal for environments with vibration or where a secure, durable hold is required. Coated with Zinc Yellow CR+3, these screws offer enhanced corrosion resistance and an attractive finish.

Enhanced Design Features:

• Increased Head Height: Built with a slightly higher head height per ASME B18.2.1 standards for better wrench engagement and reduced slippage.
• Radius Under Head: Minimizes stress concentration to improve resistance against fatigue failure.
• Smooth Washer-Bearing Surface: Provides uniform load distribution, reducing the risk of loosening under dynamic loads.

Key Mechanical Properties:

• Hardness: 38 to 42 HRC (Rockwell Hardness Scale)
• Surface Hardness: Maximum HR15N 81.5
• Tensile Strength: 180,000 PSI Minimum
• Yield Strength: 155,000 PSI Minimum
• Proof Load Strength: 145,000 PSI
• Elongation: 12% Minimum
• Reduction of Area: 35% Minimum
• Head Marking: Nine radial lines with "L9" for easy identification

Advanced Surface Finish:

• Zinc Yellow Plated: Conforms to ASTM F1941/F1941M Fe/Zn 5CN standards with a minimum thickness of 5 microns (0.0002").
• Yellow Trivalent (Cr+3) Coating: Provides excellent corrosion resistance, with 96 hours of protection before red rust appears in salt spray testing.

Technical Specifications:

• Size: 5/16"-24 (Diameter: 0.3125", Threads per Inch: 24)
• Length Options: Available in various lengths to meet specific requirements (please select from options above)
• Material: High-Grade Alloy Steel (L9)
• Finish: Zinc Yellow CR+3 Plating for superior corrosion resistance
• Thread Type: Fine Thread (UNF)
• Manufactured In: United States

Ideal Applications:

Our 5/16"-24 L9 Hex Head Cap Screws with fine threads are ideal for applications where strength and vibration resistance are paramount, including automotive engines, machinery, heavy equipment, and construction assemblies. Built for ultimate reliability, they’re ready to support your most challenging projects.

Full L9 Product Line

Place Your Order Today!

Ensure the stability and security of your assemblies with our 5/16"-24 L9 Hex Head Cap Screws. Order now for fast shipping and quality you can trust, exclusively from Monster Bolts.