7/8-9 Flat Head Cap Screw

The 7/8"-9 Flat Head Cap Screw is an ultra-heavy-duty, flush-mount fastener engineered for large-scale structural, mechanical, and industrial assemblies where maximum strength and a clean, unobtrusive finish are required. Designed with an 82° countersunk flat head and an internal hex socket, this fastener delivers high torque capacity, secure thread engagement, and a flush installation surface to reduce interference in demanding environments.

Specifications

• Thread Size: 7/8"-9 (Unified National Coarse)

• Head Type: Flat head with 82° countersink and internal hex drive

• Drive Type: Hex socket (Allen)

• Length: Available in standard lengths (typically from 1-1/2" to 6"+)

• Material: Alloy steel; also available in stainless steel, black oxide, or zinc-plated carbon steel

• Finish Options: Black oxide, plain, zinc-plated, or stainless

• Grade: Typically Grade 8 (hardened alloy steel) or 18-8 / 316 stainless steel for corrosion resistance

Key Features

• Flush Countersunk Head: Allows the screw to seat level with or below the surface, preventing snag points and improving overall safety and appearance.

• Maximum Strength Design: The 7/8" diameter and coarse 9 TPI thread offer exceptional tensile and shear resistance, suitable for extreme load-bearing conditions.

• Secure Hex Drive: Internal hex socket ensures precise, high-torque tightening with reduced risk of head stripping or tool slippage.

• Finish Versatility: Coated and stainless variants support long-term performance in corrosive, marine, or outdoor environments.

• Precision Threading: Machined to UNC standards for reliable mating with tapped holes or structural-grade nuts.

Typical Applications

The 7/8"-9 Flat Head Cap Screw is built for high-load, flush-mounted structural and mechanical systems, including:

• Structural Steel and Support Columns

• Heavy Equipment and Machinery Frames

• Industrial Presses, Dies, and Base Plates

• Bridge and Infrastructure Fastening

• Transportation, Crane, and Rigging Hardware

• Marine and Offshore Platform Assemblies (stainless steel)