National Mfg N350-785 3.5in Ss Spring Door Hinge Ul Fire

Product Description

The NATIONAL MFG/SPECTRUM BRANDS HHI N350-785 is a 3.5-inch stainless steel spring-loaded door hinge designed for adjustable self-closing door applications. Manufactured from cold rolled steel with a stainless steel finish, this hinge provides both adjustable closing speed and adjustable spring tension, allowing installers to fine-tune door behavior after installation. The square-corner profile fits standard hinge cutouts without modification. It is UL approved for use on fire doors, making it suitable for code-required fire-rated door assemblies in residential and light commercial construction. Each package contains two hinges.

This hinge is used in applications where a door must self-close consistently, including fire-rated corridor doors, stairwell access doors, and utility room entries. The adjustable tension and closing speed make it well-suited for installations where door weight and swing resistance vary. It fits standard hinge cutouts, so it drops into existing mortises without additional prep work. Carpenters, general contractors, and facility maintenance professionals are the primary installers. The UL fire-door listing makes it appropriate wherever local building codes require self-closing hardware on fire-rated assemblies.

Key Features

• UL approved for fire-rated door assemblies
• Adjustable closing speed for fine-tuned door control
• Adjustable spring tension to accommodate varying door weights
• Fits standard hinge cutouts with square-corner profile — no mortise modification required
• Constructed from cold rolled steel with stainless steel finish for corrosion resistance
• Sold as a package of two hinges

Compatibility

Designed as an OEM-style replacement or new-installation self-closing hinge for standard 3.5-inch hinge cutout fire-rated and non-fire-rated doors in residential and light commercial applications.

Installation Notes

Installation is typically performed by a carpenter, door hardware installer, or licensed general contractor. Ensure the door is properly supported and the frame is plumb and square before mounting. Adjust closing speed and spring tension only with the door hanging and hardware fully secured, using the adjustment tool or hex key appropriate to the hinge mechanism. Where fire-door ratings are required, verify the full assembly — door, frame, and hardware — meets the applicable local building and fire code requirements before sign-off.