National Mfg N350-850 4in Oil Rubbed Bronze Spring Door Hinge

Product Description

The NATIONAL MFG/SPECTRUM BRANDS HHI N350-850 is a 4-inch oil rubbed bronze spring-loaded door hinge designed for self-closing door applications. Manufactured from cold rolled steel, it features independently adjustable closing speed and tension, allowing installers to dial in the right close rate for the door weight and frequency of use. The hinge carries UL approval for fire door installations, making it a code-compliant choice where rated assemblies are required. It ships in a package quantity of two, covering a standard single-door installation. Carpenters, general contractors, and door hardware installers are the typical trades working with this product.

This hinge is suited for residential and light commercial interior door installations where a self-closing function is required. The 1/4-inch radius round corners and standard hinge cutout dimensions allow it to drop into existing hinge mortises without modification in most cases. Its UL listing for fire doors makes it appropriate for rated corridor and stairwell doors in commercial occupancies where self-closing hardware is mandated by code. The oil rubbed bronze finish suits applications where a dark, matte hardware aesthetic is specified.

Key Features

• Adjustable closing speed allows field tuning to match door weight and use frequency
• Adjustable spring tension for consistent self-closing performance over time
• UL approved for fire door assemblies, supporting code-compliant rated installations
• Fits standard hinge cutout mortises without modification
• 1/4-inch radius round corners for compatibility with standard door prep
• Cold rolled steel construction with oil rubbed bronze finish
• Sold as a pack of two hinges

Compatibility

Designed as an OEM-style replacement or upgrade hinge for standard residential and light commercial doors with a 4-inch hinge mortise prep, including UL-listed fire door assemblies where self-closing hardware is required.

Installation Notes

Installation is typically performed by a carpenter, door hardware installer, or general contractor. Before installation, confirm the door and frame mortises match the 4-inch hinge dimensions and 1/4-inch corner radius. On fire-rated assemblies, verify that all components of the door assembly maintain the required UL listing and consult local building codes for self-closing hardware requirements. Adjust closing speed and tension using the hinge adjustment screws after the door is hung and hardware is fully fastened.