Soss 418SSICUS32D Fire Rated Invisible Spring Hinge

Product Description

The SOSS UIP ALLEGION 418SSICUS32D is a heavy-duty, fire-rated invisible spring hinge designed for commercial and residential door installations requiring a concealed hardware profile. Measuring 1-1/8 inches by 4-39/64 inches, this hinge installs fully within the door and frame mortise, leaving no visible hardware when the door is closed. The satin stainless steel finish provides corrosion resistance suited to high-traffic or moisture-prone environments. The integrated spring mechanism returns the door to a closed position automatically, making it appropriate for fire-rated door assemblies where self-closing hardware is required by code.

This hinge is intended for 1-3/4 inch thick doors in applications where concealed hardware is specified, such as commercial offices, healthcare facilities, hospitality interiors, and high-end residential builds. It is sold individually (EA) and is appropriate for projects where door aesthetics are critical and surface-mounted hinges are not acceptable per design specifications. Licensed carpenters, finish contractors, and door hardware installers are the typical tradespeople specifying and installing this product.

Key Features

• Fully invisible installation — no exposed hardware visible when door is closed
• Fire-rated construction suitable for fire-rated door assemblies requiring self-closing hardware
• Integrated spring mechanism provides automatic door return
• Satin stainless steel finish (US32D) for corrosion resistance in demanding environments
• Heavy-duty rating for high-cycle commercial door applications
• Designed for 1-3/4 inch thick doors

Compatibility

Designed for use with 1-3/4 inch thick doors requiring a concealed, fire-rated self-closing hinge. Consult local building and fire codes to confirm suitability for specific fire-rated door assembly listings.

Installation Notes

Installation requires precise mortise routing in both the door edge and the door frame jamb; a router and manufacturer-specified template are the standard tools for this work. Power down or disable any electrified hardware in the door assembly before beginning installation. This product is intended for installation by qualified door hardware professionals or licensed finish carpenters familiar with fire-rated door assembly requirements under applicable building codes. Verify that the completed assembly meets the fire-rating listing requirements of the door, frame, and hardware as a combined unit before closing out the installation.