5/8"-18 L9 Hex Head Cap Screw – Fine Thread Alloy Steel Zinc Yellow CR+3 (Made in U.S.A.)

5/8"-18 L9 Hex Head Cap Screw – Fine Thread Alloy Steel Zinc Yellow CR+3 (Made in U.S.A.)

Our 5/8"-18 L9 Hex Head Cap Screws bring unparalleled strength and reliability to high-demand applications. These premium screws are manufactured in the USA from high-grade alloy steel, offering an exceptional tensile strength of 180,000 PSI. Ideal for critical projects requiring enhanced durability, these screws meet the toughest standards for secure fastening in dynamic environments.

Why Choose L9 Hex Head Cap Screws?

L9 fasteners represent the highest SAE grade for hex cap screws, specially engineered for applications where maximum strength is a priority. Identified by nine radial lines and the "L9" marking, these screws are known for their superior performance. The fine thread (UNF) design allows for greater holding power and better clamp load distribution, while the Zinc Yellow CR+3 finish ensures exceptional corrosion resistance and durability.

Enhanced Design Features:

• Increased Head Height: Slightly taller than standard hex heads, allowing for more secure wrenching and reduced slippage.
• Radius Under Head: Reduces stress concentrations, enhancing resistance against fatigue failure.
• Smooth Washer-Bearing Surface: Provides even load distribution to prevent loosening in high-stress settings.

Key Mechanical Properties:

• Hardness: 38 to 42 HRC
• 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 identification

Advanced Surface Finish:

• Zinc Yellow Plated: Compliant with ASTM F1941/F1941M Fe/Zn 5CN standards, providing a minimum thickness of 5 microns (0.0002").
• Yellow Trivalent (Cr+3) Coating: Delivers 96 hours of salt spray protection for reliable corrosion resistance.

Technical Specifications:

• Size: 5/8"-18 (Diameter: 0.625", Threads per Inch: 18)
• Length Options: Various lengths available for specific application needs (select above)
• Material: High-Grade Alloy Steel (L9)
• Finish: Zinc Yellow CR+3 Plating for maximum corrosion resistance
• Thread Type: Fine Thread (UNF)
• Manufactured In: United States

Ideal Applications:

Our 5/8"-18 L9 Hex Head Cap Screws with fine threading are ideal for securing critical assemblies in industries such as automotive, aerospace, heavy machinery, and construction. Built for high-stress applications, they are designed to hold strong in challenging conditions.

Full L9 Product Line

Order Yours Today!

Ensure the stability and strength of your assemblies with our 5/8"-18 L9 Hex Head Cap Screws. Order now to receive fast shipping and reliable customer service from Monster Bolts, trusted by professionals worldwide.