Electro Hardware S521-M07-F16-E Circuit Board Spacer

Product Description

The ELECTRO HARDWARE S521-M07-F16-E is a round, female unthreaded circuit board spacer designed to maintain precise standoff distances between PCBs and mounting surfaces in electronic assemblies. Built from 18-8 and 303 grade stainless steel with a bright uncoated finish, this spacer meets the QQ-S-763 fastener standard. It measures 0.375 inches overall length with an outside diameter of 0.25 inches and an inside diameter of 0.116 inches, sized for number 4 screw hardware. Electricians, controls technicians, and electronics assembly professionals use these spacers when building or servicing control boards in HVAC units, motor controls, and similar equipment.

This spacer is suited for use in both residential and light commercial electronic control assemblies where board isolation, vibration resistance, and corrosion resistance are required. The stainless steel construction makes it appropriate for environments where moisture or mild chemical exposure is a concern, such as rooftop units or outdoor control enclosures. Its female unthreaded body accepts a number 4 screw passed through a mounting hole in the PCB or panel.

Key Features

• 18-8 and 303 grade stainless steel construction for corrosion resistance
• Meets QQ-S-763 fastener standard for quality assurance
• Female unthreaded body accepts number 4 screw hardware
• 0.375 inches overall length with tight length tolerance of -0.005 to 0.005 inches
• Inside diameter tolerance of 0.000 to 0.010 inches for consistent fit
• Bright uncoated finish - no coating to degrade or flake in service

Compatibility

Designed as an OEM-style replacement or direct-use standoff spacer for control board assemblies requiring a round, female unthreaded number 4 screw size spacer with 0.375 inches overall length.

Installation Notes

Installation is typically performed by licensed electricians or controls technicians during board mounting or replacement procedures. Always de-energize the control panel and verify zero voltage with a meter before handling any PCB or spacer hardware. Use hand tools appropriate for number 4 fasteners and avoid over-tightening, which can crack PCB substrates. Follow applicable NEC guidelines for control wiring and enclosure work.