Electro Hardware S517-M10-F21-H Round Board Spacer 5/16in

Product Description

The ELECTRO HARDWARE S517-M10-F21-H is a round, female unthreaded circuit board spacer designed to create precise standoff clearance between a PCB and its mounting surface. Constructed from Grade 2 steel with a zinc-plated finish meeting ASTM B633 and QQ-S-633 Type 1 standards, this spacer provides reliable corrosion resistance and dimensional consistency. It accepts a Number 8 screw, measures 0.3125 inches overall length, 0.25 inches outside diameter, and 0.171 inches inside diameter. Electronics technicians, HVAC controls installers, and electrical panel assemblers use this type of hardware when mounting control boards in equipment enclosures.

This spacer is suited for use in residential and commercial electronic assemblies where a consistent standoff gap is required between a circuit board and a chassis or sub-panel. Typical applications include control board mounting in HVAC units, electrical enclosures, and industrial control panels. The female unthreaded design accepts a Number 8 fastener passed through the board and into the spacer body, allowing the board to sit at a fixed, repeatable height above the mounting surface.

Key Features

• Female unthreaded body accepts Number 8 screws for straightforward board mounting
• Grade 2 steel construction with zinc-plated finish per ASTM B633 and QQ-S-633 Type 1
• Overall length of 0.3125 inches with a tight length tolerance of -0.005 to 0.005 inches
• Inside diameter of 0.171 inches with tolerance of 0.000 to 0.010 inches for consistent fit
• Round body shape with 0.25 inches outside diameter for compact footprint on crowded boards
• Inch system of measurement for direct compatibility with standard US fastener layouts

Compatibility

Designed as an OEM-style replacement or new-installation spacer for circuit board mounting applications requiring a Number 8 screw, 0.3125-inch standoff height, and a female unthreaded round body in inch dimensions.

Installation Notes

Installation is performed by electronics technicians or qualified electricians during control board assembly or replacement. Always de-energize the equipment and discharge any stored capacitance before handling circuit boards or installing standoff hardware. Use a screwdriver or nut driver sized for the Number 8 fastener and do not overtighten, as excessive force can crack the PCB substrate or deform the spacer. Follow applicable NEC guidelines when working inside electrical enclosures.