SOSS 420SS Stainless Steel Inv...
IN STOCK (leaves warehouse same day if ordered before 3pm ET)
$570.00
$365.00
SOSS 420SS Stainless Steel Invisible Hinge with 3-Hour Fire Rating

SOSS 420SS Stainless Steel Invisible Hinge with 3-Hour Fire Rating

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Model: 420SSUS32D

In Stock (leaves warehouse same day if ordered before 3pm ET)

$570.00
$365.00
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SOSS 420SS Stainless Steel Invisible Hinge with 3-Hour Fire Rating

The SOSS 420SS Invisible Hinge is engineered for metal door applications requiring a minimum material thickness of 2", delivering a fully concealed, flush-fit appearance combined with heavy-duty commercial performance. Constructed of complete 316 stainless steel, this single-action hinge opens a full 180° and is Underwriters Laboratories labeled for use on hollow metal, sheet metal, tin clad, and steel composite swinging fire doors and frames rated up to and including 3 hours, as well as wood core doors and frames rated up to 20 minutes. Ideal for exterior and full-sized entry applications where corrosion resistance, compact size, and smooth operation are essential.

Key Features

  • Material Thickness Compatibility: Designed for metal applications with a minimum material thickness of 2".
  • Product Size: 4-1/2" hinge size for full-sized entry door applications.
  • Fire-Rated Performance: UL labeled for use on hollow metal, sheet metal, tin clad, and steel composite fire doors and frames rated up to and including 3 hours (180 minutes), and wood core doors and frames rated up to 20 minutes.
  • Full 180° Single-Action Operation: Provides smooth, reliable swing for full-sized entry doors.
  • Heavy-Duty Stainless Steel Construction: Made of complete 316 stainless steel for superior corrosion resistance and durability in exterior and demanding commercial environments.
  • Concealed, Flush-Fit Design: Compact, invisible profile maintains a clean door appearance while delivering dependable operation.
  • Machine Screws Included: Ships complete with machine screws for straightforward installation.
  • Fire Door Hinge Quantity Guidance: Use at least one fire-rated hinge for every 20" of door height (or portion thereof), or one hinge for every 60 lbs. (or fraction thereof), whichever calculation demands more hinges.

Certifications & Compliance

  • Underwriters Laboratories (UL) Labeled
  • Fire Rated up to 3 Hours (180 Minutes) on Metal Doors and Frames
  • Fire Rated up to 20 Minutes on Wood Core Doors and Frames

Technical Specifications

  • Subcategory: Hinges and Pivots
  • Product Group: Door Hinges and Pivots
  • Product Subgroup: Concealed Hinges
  • Commercial/Residential: Commercial
  • Duty Level: Heavy Duty
  • Electronic: No
  • Corner Type: Square
  • Series: 420 Series
  • Product Finish: US32D - Satin Stainless Steel
  • Product Size: 4-1/2"
  • Product Category: Door Hinges and Pivots
  • Department: Door Hardware
  • Application: Exterior, Full Sized Entry, Metal
  • Min. Material Thickness: 2″
  • Fire Rating: 180 Minutes
  • Power Transfer: No
  • Closer: No
  • Counter Bored Screw Holes: No
  • Screws Included: Machine
  • Packaging: 1 / Box = 1 Each
  • Packages Per Container: 1 Each
  • Price Per: Each

Typical Applications

  • Commercial Office Buildings
  • Educational Facilities
  • Healthcare Institutions
  • Retail Establishments
  • Industrial and Warehouse Facilities
  • Government and Municipal Buildings
  • Exterior Full-Sized Entry Doors

Why SOSS 420 Series?

SOSS 420 Series hinges deliver professional-grade reliability with complete 316 stainless steel construction rated for use on UL labeled fire doors up to 3 hours. Engineered for demanding commercial applications where a concealed appearance, corrosion resistance, and dependable 180° single-action operation are essential.

Product Specs

Subcategory:
Hinges and Pivots
Product Group:
Door Hinges and Pivots
Product Type:
Invisible Hinges
Product Subgroup:
Concealed Hinges
Commercial/Residential:
Commercial
Duty Level:
Heavy Duty
Electronic:
No
Corner Type:
Square
Series:
420 Series
Product Function:
Invisible Hinges
Product Finish:
US32D - Satin Stainless Steel
Product Size:
4-1/2"
Product Category:
Door Hinges and Pivots
Product Substrate:
Stainless Steel
Department:
Door Hardware

SOSS 420SSUS32D – Frequently Asked Questions

1) Will a SOSS 420SS invisible hinge work on a 1-3/4 inch hollow metal door?
No. The 420SS needs a minimum material thickness of 2 inches, so a standard 1-3/4 inch commercial door is too thin for it. The hinge body is concealed inside the door edge and the jamb, and that routing depth is what drives the 2 inch requirement. If your opening is 1-3/4 inch, you need a smaller invisible hinge from the SOSS range rather than the 420.
2) Is the SOSS 420SS fire rated, and for how long?
Underwriters Laboratories labeled, up to and including 3 hours (180 minutes) on hollow metal, sheet metal, tin clad and steel composite swinging fire doors and frames. On wood core doors and frames the label is 20 minutes. So the same hinge covers a 3-hour stair or corridor opening in metal and a 20-minute wood opening, but do not carry the 180 minute number over to a wood door.
3) Will a SOSS 420SS hold up on an exterior entry door?
That is what it is built for. The 420SS is complete 316 stainless steel, the grade specified where corrosion resistance matters, and it is listed for exterior, full sized entry and metal applications at a heavy duty commercial level. The visible finish is US32D satin stainless. Coastal and washdown environments are the case for 316 over a plated steel hinge.
4) How far does a SOSS 420SS invisible hinge open?
A full 180 degrees, single action. That is a door swinging flat back against the wall in one direction only, not a double acting swing. For openings where furniture or gurney traffic needs the leaf fully out of the way, the 180 degree swing is the reason to pick a concealed hinge over a butt hinge that stops shorter.
5) Should I use an invisible hinge or a standard butt hinge on a commercial metal door?
An invisible hinge like the 420SS is the choice when you want no hardware visible on the door edge with the door closed, and a flush, clean face. It routes into the door and jamb, so the prep is a mortise pocket rather than a surface leaf, and the door thickness has to be at least 2 inches. A butt hinge is faster to install, works on thinner doors, and is easier to swap. Pick the concealed hinge for appearance and security of the pin, the butt hinge for simple replacement work.
6) Does the SOSS 420SS come with screws, or do I need to buy fasteners?
Machine screws ship with the hinge. That is the correct fastener type for the metal doors and frames it is labeled for, since the prep is tapped rather than relying on wood threads. Nothing else is included in the box, which holds one hinge.
7) Can the SOSS 420SS carry power to an electrified lock?
No. The 420SS is a mechanical hinge with no electric power transfer through it and no closer function. If the opening needs power to an electric strike, electrified lever trim or a mag lock, run it through a separate power transfer device or a raceway, and specify the door closer separately.
8) Can I standardize on one invisible hinge across metal and wood fire doors in my building?
The 420SS covers both, within different ratings. On hollow metal, sheet metal, tin clad and steel composite doors and frames it is labeled up to 3 hours; on wood core doors and frames it is labeled to 20 minutes. Both doors also need at least 2 inches of material thickness for the hinge to be prepped into, which is the practical limit on standardizing, since many wood leaves are thinner than that.
9) Are the screw holes on the SOSS 420SS counterbored?
They are not counterbored on the 420SS. The machine screw heads seat in the plain holes as machined, so do not plan on a flush countersunk head or on substituting a flat head screw to sit below the surface. Use the screws supplied.
10) What is the exact part number and finish to order for a SOSS 420 stainless invisible hinge?
SOSS model 420SS, in US32D satin stainless steel. That is the single configuration in the 420 Series stainless offering, so there is no separate finish or handing code to add; the hinge is symmetrical single action and is sold one per box.
How fast can I get the SOSS 420SSUS32D delivered?
Most orders ship the same day from our distribution partners, with quick delivery throughout the continental U.S. Need it urgently? Contact Us for expedited shipping options.
Can I return it if it doesn’t work for me?
Yes—ZenSupply offers a hassle-free return policy. If the product isn’t the right fit, reach out to our support team for a return authorization or setup a return by following our return instructions.
Does the SOSS 420SSUS32D come with a warranty?
Absolutely. The SOSS 420SSUS32D is backed by a manufacturer’s warranty. For full warranty terms, check the product documentation or Contact Us.
How do I get technical support or installation help for the SOSS 420SSUS32D?
You can call, text, or email our expert support team for fast answers. We’re here to help with product selection, installation tips, and troubleshooting. Contact Us
Why buy the SOSS 420SSUS32D from ZenSupply?
ZenSupply makes it easy to get the commercial door hardware you need—fast shipping, expert support, and rewards on every order. Our team is always ready to help you choose the right product for your project.
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