Electro Hardware S521-M01-F21-G Circuit Board Spacer No. 6

Product Description

The ELECTRO HARDWARE S521-M01-F21-G is a round, female unthreaded circuit board spacer designed to maintain precise standoff distances between PCBs and mounting surfaces in electronic assemblies. Built from brass to ASTM B633 and QQ-B-626 Comp 22 Type 1 standards, the spacer carries a zinc-plated finish for corrosion resistance. It measures 0.375 inches overall length with a 0.25-inch outside diameter and a 0.141-inch inside diameter. This fastener is sized for No. 6 screws and is installed by electronics assembly technicians, field service engineers, and electricians working with control boards in HVAC, electrical, or industrial equipment.

This spacer suits applications where consistent board standoff is required in control panel assemblies, terminal boards, and circuit board mounting configurations. Its female unthreaded body accepts a No. 6 screw passed through from the mounting surface side, allowing secure stacking or spacing of PCBs without threading into the spacer itself. Typical use cases include residential and commercial HVAC control board mounting, electrical enclosure assemblies, and light industrial electronic equipment where dimensional precision and corrosion resistance are required.

Key Features

• Brass construction meets ASTM B633 and QQ-B-626 Comp 22 Type 1 fastener standards
• Zinc-plated finish provides corrosion resistance in control panel environments
• Female unthreaded body sized for No. 6 screws
• Overall length of 0.375 inches with tight length tolerance of -0.005 to 0.005 inches
• Inside diameter tolerance of 0.000 to 0.010 inches for consistent fitment
• Round body shape for uniform load distribution on PCB mounting surfaces

Compatibility

Designed as an OEM-style replacement or new-installation spacer for No. 6 screw circuit board mounting applications in residential and commercial control panel assemblies.

Installation Notes

Installation is performed by qualified electricians or electronics assembly technicians. De-energize all circuits and discharge any capacitors before servicing control boards or electronic assemblies. Verify that the No. 6 screw used does not exceed the inside diameter tolerance range, as forcing an oversized fastener can crack the spacer or damage the PCB. Follow applicable NEC guidelines for electrical enclosure work when replacing control board hardware.