Holo-krome 77540 Hex Socket Cap Screw 1/2-20 Unf 4 in

Product Description

The HOLO-KROME 77540 is a hex socket cap screw designed for high-strength fastening applications in mechanical, industrial, and equipment assembly work. It features a 1/2-20 UNF thread size and a 4-inch length under head, with partial threading along the shank. The drive is a 3/8-inch internal hex socket, requiring an Allen key or hex driver for installation. Constructed from alloy steel with a black oxide finish, this fastener delivers corrosion resistance and maintains dimensional integrity under torque. Machinists, millwrights, and industrial maintenance technicians commonly specify this fastener where tight tolerances and high clamping force are required.

This screw is suited for precision mechanical assemblies, machinery frames, fixtures, jigs, and structural equipment where a UNF fine-thread fastener is specified. The partial threading engages mating threads in tapped holes while the unthreaded shank provides shear strength across joint interfaces. The black oxide coating is appropriate for indoor and low-exposure applications. It meets ASME B18.3 and ASTM A574 standards, making it compatible with engineering specs that reference those fastener standards.

Key Features

• 1/2-20 UNF fine thread for precise engagement and high clamping force
• 4-inch length under head with partial threading along the shank
• 3/8-inch hex socket drive for use with standard Allen keys or hex drivers
• Alloy steel construction meets ASTM A574 high-strength socket cap screw specification
• Black oxide finish provides mild corrosion resistance and reduces light reflection
• Conforms to ASME B18.3 dimensional standard for socket cap screws

Compatibility

Designed as a standard ASME B18.3 hex socket cap screw for use in any tapped hole or application specifying a 1/2-20 UNF partially threaded socket cap screw in alloy steel.

Installation Notes

Installation is performed by machinists, millwrights, or maintenance technicians using a 3/8-inch hex key or Allen driver. Ensure the mating tapped hole meets ASME B18.3 thread engagement requirements before installation. De-energize, depressurize, or lock out the equipment per OSHA LOTO procedures before fastener replacement in live machinery. Do not substitute a coarse-thread fastener in a UNF-specified hole.