Electro Hardware S577-M10-F21-H Round Circuit Board Spacer

Product Description

The ELECTRO HARDWARE S577-M10-F21-H is a round, female unthreaded circuit board spacer designed to create precise standoff clearance between a PCB and a mounting surface or between stacked boards. Machined from Grade 2 steel with a zinc-plated finish per ASTM B633 and QQ-S-633 Type 1, this spacer provides corrosion resistance in light-duty service environments. It accepts a Number 8 screw through its 0.171-inch inside diameter bore and measures 1.25 inches in overall length with a 0.25-inch outside diameter. Electronics technicians, control board assemblers, and field service techs working on HVAC control boards, electrical panels, and similar equipment use this hardware for consistent board mounting.

This spacer is suited for residential and light commercial electronic assemblies where a Number 8 fastener is used to mount circuit boards to enclosures, chassis, or DIN-mounted subpanels. Typical applications include HVAC control board replacements, motor drive assemblies, and general electrical enclosure builds where fixed standoff height and electrical isolation clearance are required. The female unthreaded design allows a screw to pass through freely, seating the board at a fixed height without threading into the spacer body itself.

Key Features

• Female unthreaded bore accepts Number 8 screws with 0.171-inch inside diameter
• 1.25-inch overall length with tight length tolerance of -0.005 to 0.005 inches for consistent standoff height
• 0.25-inch outside diameter round body fits standard PCB mounting hole patterns
• Zinc-plated steel finish meets ASTM B633 and QQ-S-633 Type 1 standards for corrosion resistance
• Grade 2 steel construction provides reliable mechanical strength for panel and board mounting
• Inside diameter tolerance of 0.000 to 0.010 inches ensures consistent fastener fit

Compatibility

Designed as an OEM-style replacement or new-install standoff spacer for circuit board assemblies using Number 8 screws in inch-measurement systems.

Installation Notes

Installation should be performed by a qualified technician. Always de-energize the equipment fully and discharge any capacitors before handling circuit boards or installing standoff hardware. Use hand tools to avoid over-torquing fasteners through the unthreaded bore, which can crack the PCB or deform the spacer. Follow applicable NEC guidelines when working inside electrical enclosures.