Gardner Spring 421C Extension Spring 0.5in Od 15.58lb

Product Description

The GARDNER SPRING 421C is a steel extension spring designed for light-duty tensioning applications across HVAC, mechanical, and general industrial service work. It measures 0.5 inches in outside diameter with a wire diameter of 0.0625 inches and an overall free length of 6.0 inches. The spring extends to a maximum of 15.58 inches under a maximum work load of 15.58 pounds, with a spring rate of 3.27 pounds per inch. The zinc-plated finish provides basic corrosion resistance suitable for indoor mechanical environments. Double loop ends allow for straightforward hook or pin attachment in typical spring mounting configurations. Installation is performed by HVAC technicians, millwrights, or general maintenance professionals.

This extension spring fits a wide range of light mechanical tensioning applications including damper linkages, access panel latches, belt tensioners, and equipment door closures common in residential and light commercial HVAC systems. Its compact 0.5-inch outside diameter allows fitment in tight clearance zones where standard larger springs cannot seat properly. The 3.27 lb/in spring rate provides consistent, predictable return force suited to low-mass mechanical components.

Key Features

• 0.5-inch outside diameter for compact clearance installations
• 15.58-pound maximum work load with 15.58-inch maximum extended length
• 3.27 lb/in spring rate for consistent tensioning force
• Double loop ends for easy hook or pin attachment
• Zinc-plated steel construction for corrosion resistance in indoor service environments
• 0.0625-inch wire diameter for light-duty load applications

Compatibility

Designed as an OEM-style replacement extension spring for light mechanical tensioning applications in residential and light commercial HVAC equipment, damper assemblies, and general mechanical systems requiring a 0.5-inch OD double loop spring.

Installation Notes

Extension springs store energy under tension and must be handled carefully to prevent injury during removal and installation. Disconnect power to the equipment and release any existing spring tension before servicing. Use appropriate hooked tools or pliers rated for spring work to seat the double loop ends onto mounting pins or hooks. Do not stretch the spring beyond its rated maximum extended length of 15.58 inches, as permanent deformation or failure may result.