Electro Hardware S521M17F16H Round Circuit Board Spacer

Product Description

The ELECTRO HARDWARE S521M17F16H is a round, female unthreaded circuit board spacer designed to provide precise standoff clearance between a PCB and a mounting surface. Sized for a No. 8 screw, it measures 0.375 inches in overall length, 0.171 inches inside diameter, and 0.25 inches outside diameter. Molded from Nylon Grade 101 to the MIL-P-17091B fastener standard, it delivers consistent dimensional tolerances and a bright uncoated finish. Electronics assemblers, control board technicians, and HVAC or electrical panel builders use this spacer when mounting circuit boards in enclosures, air handlers, or control panels where non-conductive standoffs are required.

This spacer is suited for light commercial and residential PCB mounting applications where a non-metallic, electrically isolating standoff is specified. The female unthreaded bore accepts a No. 8 fastener and holds the board at a fixed 0.375-inch standoff height. Length tolerance is held to -0.005 to 0.005 inches and inside diameter tolerance to 0.000 to 0.010 inches, making it appropriate for production assemblies and field replacements alike where dimensional consistency matters. This item is sold individually but carries a minimum order quantity of 100 pieces.

Key Features

• Female unthreaded body accepts No. 8 screw for secure PCB standoff mounting
• Nylon Grade 101 construction provides electrical isolation between board and chassis
• Meets MIL-P-17091B fastener standard for dimensional and material compliance
• Tight length tolerance of -0.005 to 0.005 inches supports consistent stack height in multi-board assemblies
• Bright uncoated finish — no risk of coating flaking or contaminating board surfaces
• Lightweight at 0.01 pounds per piece, minimizing added load on PCB mounting hardware

Compatibility

Designed as an OEM-style replacement or production-use spacer for circuit board assemblies requiring a No. 8 screw, female unthreaded, round nylon standoff with a 0.375-inch overall length.

Installation Notes

Installation is performed by electronics assemblers or field technicians servicing control boards in HVAC systems, electrical enclosures, or similar equipment. Always de-energize and lock out the panel or equipment before removing or installing circuit board hardware. Use hand tools only when seating nylon spacers — power tools can crack or deform the nylon body. Verify fastener engagement does not bottom out through the spacer bore, which can crack the unthreaded wall.