Electro Hardware S521-M10-F21-G Circuit Board Spacer

Product Description

The ELECTRO HARDWARE S521-M10-F21-G is a round, female unthreaded circuit board spacer designed to maintain precise standoff distance between a PCB and a mounting surface. Built from Grade 2 steel with a zinc-plated finish per ASTM B633 and QQ-S-633 Type 1, this spacer measures 0.375 inches overall length with a 0.25 inch outside diameter and a 0.141 inch inside diameter. It accepts a No. 6 screw and is sized for applications where consistent board clearance and corrosion resistance are required. Licensed electricians, electronics technicians, and control board assembly professionals install these spacers during PCB mounting and panel assembly work.

This spacer is suited for use in residential and light commercial control panel assemblies, HVAC control boards, electrical enclosures, and electronic equipment where a No. 6 screw pattern is used. Its compact round body and standardized dimensions make it a practical choice for original-equipment and field-replacement installations requiring a reliable, low-profile standoff with female unthreaded construction.

Key Features

• Female unthreaded design accepts No. 6 screws for secure PCB standoff mounting
• Grade 2 steel construction with zinc-plated finish meets ASTM B633 and QQ-S-633 Type 1 standards
• Overall length of 0.375 inches with tight length tolerance of -0.005 to 0.005 inches for precise board clearance
• Inside diameter of 0.141 inches with tolerance of 0.000 to 0.010 inches for consistent screw fit
• Round body profile for compact installation in tight panel layouts
• Zinc plating provides corrosion resistance in indoor electrical enclosure environments

Compatibility

Designed as a standard No. 6 screw female unthreaded round circuit board spacer for PCB standoff applications in electrical control panels and enclosures.

Installation Notes

Installation is performed by licensed electricians or qualified electronics assembly technicians. De-energize and lock out the panel or equipment before servicing any control board or enclosure. Insert the spacer between the PCB and mounting surface, aligning the inside diameter with the No. 6 screw path before fastening. Do not overtighten the mating screw, as this spacer is unthreaded and relies on the fastener assembly for clamping force.