For line-shaft hardware, collars, and similar mechanical locations, 7/8-9 x 3 1/4 gives buyers the square-head set screw style named on many older drawings.

Typical applications include older machine tools that were designed around wrench-driven set screws. The five-point structure lets the same square-head size serve locating, bearing, and seating requirements. Point selection should reflect the shaft feature, acceptable marking, and expected service adjustment.

Cold Headers keeps the record focused on usable engineering details so buyers can compare the callout against drawings and service notes. Review the selected point, wrench clearance, and mating feature before substitution. The square head equals the nominal diameter across flats, giving the wrench size a direct relationship to the screw size.

Technical Highlights

• Head: Square, wrench-driven
• Material: Low Carbon Steel, Case Hardened
• Point Styles: Half Dog, Full Dog, Cone, Oval, Flat (specify at order)
• Thread Size: 7/8-9 (UNC)
• Thread Fit: 2A (per ASME B18.6.2)
• Length: 3 1/4 in.
• Width Across Flats (F): 0.875 / 0.852 in. (max/min)
• Across Corners (G): 1.237 / 1.170 in. (max/min)
• Head Height (H): 0.678 / 0.635 in. (max/min)
• Dimensional Standard: ASME B18.6.2

Call 773-775-7900 or email Sales@coldheaders.com for pricing, availability, or a quote.