Value Collection 721178PR Flat Socket Cap Screw 5/16-18 X 4 in

Product Description

The VALUE COLLECTION 721178PR is a flat socket cap screw designed for flush or countersunk fastening applications in metal assemblies. It features an 82-degree flat head profile and a 3/16-inch hex socket drive, allowing installation with a standard hex key in recessed or tight-clearance locations. The screw is manufactured from alloy steel with a black oxide finish that provides moderate corrosion resistance and reduces light reflection on the fastener surface. At 5/16-18 UNC thread and 4 inches in overall length with partial threading, this fastener suits structural joints where grip-length control and clamp load are priorities. It is sold individually with a minimum order quantity of 5 units.

This flat socket cap screw is suited for general industrial, mechanical, and light structural applications where a low-profile, flush-mount fastener is required. The partially threaded shank allows the unthreaded grip section to bear shear loads without thread engagement in the shear plane. Common installation scenarios include machinery frames, jigs and fixtures, tooling plates, and fabricated steel assemblies. It meets ASME/ANSI B18.3 and ASTM F835 fastener standards, making it appropriate for engineered connections that reference those specifications.

Key Features

• 82-degree flat head profile for flush or countersunk seating
• 3/16-inch hex socket drive for precise torque application with a standard hex key
• Alloy steel construction for high tensile strength in mechanical assemblies
• Black oxide finish for mild corrosion resistance and low-reflectance appearance
• Partial threading preserves an unthreaded shank grip section for shear-loaded joints
• Conforms to ASME/ANSI B18.3 and ASTM F835 fastener standards

Compatibility

Designed as a standard UNC replacement or new-installation fastener for 5/16-18 threaded holes requiring an 82-degree countersunk flat head and hex socket drive per ASME/ANSI B18.3.

Installation Notes

Installation is typically performed by machinists, millwrights, or maintenance technicians using a 3/16-inch hex key or hex bit driver. Ensure the mating hole is properly countersunk to 82 degrees to achieve full head seating and correct clamp load. De-energize and lock out any equipment before installing or removing fasteners in mechanical assemblies. Avoid over-torquing alloy steel screws in tapped blind holes, as thread stripping can occur without visible warning.