Electro Hardware S1391-M10-F21-H Circuit Board Spacer

Product Description

The ELECTRO HARDWARE S1391-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 adjacent board. Machined from Grade 2 steel with a zinc-plated finish per ASTM B633 and QQ-S-633 Type 1, this spacer provides a corrosion-resistant, electrically isolated standoff in panel assemblies, control boards, and electronic enclosures. It has an overall length of 1 inch, an outside diameter of 0.5 inches, and an inside diameter of 0.171 inches, making it sized for No. 8 screw hardware. Electronics assemblers, control panel builders, and field service technicians working on HVAC or industrial control boards typically install this type of fastener.

This spacer is suited for use in residential and light commercial electronic assemblies where a No. 8 fastener is the standard mounting screw. Typical applications include PCB mounting in HVAC control enclosures, electrical panels, and equipment chassis where consistent board-to-surface separation and vibration isolation are required. The female unthreaded body accepts a screw passed through from the board side, with a mating fastener securing the assembly from the opposite face.

Key Features

• Grade 2 steel construction with zinc-plated finish meets ASTM B633 and QQ-S-633 Type 1 standards
• Female unthreaded body accepts No. 8 screws for straightforward board mounting
• 1 inch overall length with tight length tolerance of -0.005 to 0.005 inches for consistent standoff height
• 0.5 inch outside diameter and 0.171 inch inside diameter with inside diameter tolerance of 0.000 to 0.010 inches
• Round body shape allows uniform load distribution across the PCB mounting point
• Zinc plating provides corrosion resistance in indoor panel environments

Compatibility

Designed as an OEM-style replacement or direct-fit standoff spacer for circuit board assemblies using No. 8 screw hardware with a required standoff height of 1 inch.

Installation Notes

De-energize and lock out all power to the control panel or enclosure before handling circuit boards or installing standoff hardware. Ensure the mating screw length is appropriate for the spacer length plus board thickness to avoid bottoming out or insufficient clamping force. Use standard hand tools and follow applicable assembly torque guidelines for No. 8 fasteners to avoid stripping the unthreaded bore or cracking the PCB. Verify spacer seating is flat and even before securing the board.