Holo-krome 60090 Flat Socket Cap Screw 5/16-18 X 2-1/4 in

Product Description

The HOLO-KROME 60090 is a flat socket cap screw designed for flush or countersunk fastening applications in mechanical assemblies, tooling fixtures, and structural components. It features an 82-degree flat head with a 3/16-inch hex socket drive, allowing installation with a standard hex key. The fastener is partially threaded and sized at 5/16-18 UNC, 2-1/4 inches in overall length. Manufactured from alloy steel with a black oxide finish, it carries a hardness rating of 39-44 HRC and conforms to ASME B18.3 and ASTM F835 standards. Licensed tradespeople, machinists, and maintenance technicians are the primary installers.

This screw is suited for applications where a low-profile, countersunk head is required and a protruding fastener head is not acceptable. Common uses include machine tool construction, jigs, dies, and industrial equipment assembly. The partial threading provides strong clamping force when fastening through clearance holes into tapped bores. The black oxide finish provides mild corrosion resistance and reduces light reflection in precision environments. This is a sold-in-multiples item with a minimum order quantity of 10 pieces, packaged as single units.

Key Features

• 82-degree flat head profile for flush countersunk installations
• 3/16-inch hex socket drive compatible with standard hex keys and Allen drivers
• Alloy steel construction with 39-44 HRC hardness for high-strength fastening
• Black oxide finish for mild corrosion resistance and low-reflectance surface
• Partially threaded shank for secure clamping in clearance-hole applications
• Meets ASME B18.3 and ASTM F835 fastener standards

Compatibility

Designed as an OEM-style replacement or direct-use flat socket cap screw for 5/16-18 UNC tapped holes requiring a countersunk head per ASME B18.3 specifications.

Installation Notes

Installation is typically performed by machinists, millwrights, or maintenance technicians using a calibrated torque wrench with a 3/16-inch hex bit. Before installation, confirm the mating hole is properly countersunk to 82 degrees to ensure full head seating. Do not use an impact driver, as it may damage the hex socket recess or over-torque the fastener. Follow applicable ASME or equipment manufacturer torque specifications for 5/16-18 alloy steel fasteners.