Bowmalloy 36166 Hex Head Cap Screw 5/8-11 X 8.5 in Grade 9

Product Description

The BOWMALLOY 36166 is a partially threaded hex head cap screw designed for high-strength fastening applications in structural, industrial, and mechanical assemblies. It is manufactured from Grade 9 alloy steel, which delivers tensile strength above standard Grade 5 and Grade 8 fasteners, making it a go-to choice where elevated load and shear demands are present. The 5/8-11 thread size and 8.5-inch length under head allow this screw to span thick material stacks while maintaining full clamping force. A zinc-plated clear chromate finish provides baseline corrosion resistance suitable for general service environments. Licensed contractors, millwrights, ironworkers, and maintenance mechanics are the primary installers of this fastener.

This cap screw is suited for heavy-duty structural connections, equipment mounting, and machinery fabrication where Grade 9 alloy steel performance is specified. Its partial threading preserves shank strength in the bearing zone, which is critical in bolted joints subject to dynamic or shear loading. Typical applications include steel fabrication, agricultural equipment, mining machinery, and industrial frame assembly. The inch-system 5/8-11 UNC thread pattern is compatible with standard hex nuts and washers of the same thread specification.

Key Features

• Grade 9 alloy steel construction for high tensile and proof-load strength
• 5/8-11 UNC thread size with partial threading for shear-zone shank integrity
• 8.5-inch length under head accommodates thick material stacks and deep clearance holes
• Zinc-plated clear chromate finish for general corrosion protection
• Inch-system dimensioning for compatibility with standard UNC hardware

Compatibility

Designed for use with standard 5/8-11 UNC hex nuts, flat washers, and lock washers in inch-system fastener assemblies across industrial, structural, and mechanical applications.

Installation Notes

Installation should be performed by a qualified mechanic, ironworker, or millwright following applicable torque specifications for Grade 9 fasteners as published in the relevant ASME or AISC standards. Always use a calibrated torque wrench and apply the correct fastener lubricant or anti-seize compound if specified by the joint design. Inspect the mating threads and bearing surfaces for damage or contamination before assembly. Do not use an impact driver at full power during final tightening, as this can lead to inaccurate clamp load.