Electro Hardware P521M12F21-440 Hex Standoff 4-40

Product Description

The ELECTRO HARDWARE P521M12F21-440 is a female hex circuit board standoff designed to create fixed spacing between PCBs, mounting plates, and enclosure panels. Machined from Grade 2 steel with a zinc-plated clear chromate finish meeting ASTM B633 Type 1 and QQ-S-633 standards, this standoff provides corrosion resistance appropriate for indoor electronic assemblies. The female thread accepts a 4-40 fastener at the top, with an overall length of 0.375 inches and a hex body measuring 0.25 inches across flats. It is installed by electronics assemblers, field service technicians, and electrical panel builders who need reliable, repeatable board-to-surface clearance.

This standoff is sized for compact PCB mounting applications where 4-40 thread engagement is specified. The 0.375-inch overall length suits low-profile stacking arrangements in control panels, terminal enclosures, and electronic equipment chassis. It is appropriate for residential and light commercial control board assemblies, as well as industrial electronics where standardized inch-system fasteners are required. The hex body shape allows installation with a standard hex wrench or nutdriver without slippage.

Key Features

• Female 4-40 thread accepts standard 4-40 machine screws for secure board mounting
• Hex body profile allows torque application with a nutdriver or open-end wrench
• Zinc-plated clear chromate finish meets ASTM B633 Type 1 and QQ-S-633 for corrosion resistance
• Grade 2 steel construction provides consistent thread integrity under repeated assembly cycles
• Length tolerance held to plus or minus 0.005 inches for predictable stack height
• Inch system dimensioning compatible with standard 4-40 hardware throughout the assembly

Compatibility

Designed as a standard-duty OEM-style hex standoff for PCB mounting applications using 4-40 inch-system fasteners in electronic enclosures, control panels, and circuit board assemblies.

Installation Notes

Installation is performed by electronics assemblers or qualified service technicians. De-energize all circuits and discharge any capacitors before working inside control panels or electronic enclosures. Use a properly sized nutdriver or hex wrench to drive the standoff to snug contact without over-torquing, which can strip the 4-40 thread or crack the board. Follow the equipment manufacturer's fastener seating specifications and any applicable NEC requirements for the enclosure type.