About this item
On most commercial door schedules, the 4-1/2" x 4-1/2" full mortise ball bearing hinge is the workhorse. It's on office doors, classroom doors, hospital patient room doors, hotel corridor doors, and virtually every interior commercial opening in between. The Cal-Royal TABB31 is the template version of that hinge: a full mortise, standard weight, two ball bearing hinge in the 4-1/2" x 4-1/2" square format, sold in a box of three, and built to ANSI A156.1, A156.7, and A156.18 standards. If you're sourcing hinges for a standard commercial door schedule and you need a reliable, code-compliant hinge that installs without modification on hollow metal or wood frame doors, this is the correct product.
For companion spring hinges for fire-rated self-closing assemblies, browse our commercial spring hinges. For all commercial hinge types across every size and weight class, view our full commercial door hinges selection.
Why Ball Bearing Hinges Outperform Plain Bearing Hinges
Plain bearing hinges work fine on low-frequency doors. The moment you put a plain bearing hinge on a door that gets opened and closed dozens or hundreds of times a day, you start hearing it. The friction point between the pin and the knuckle wears, the hinge starts squeaking, and eventually the pin channels wallow out and the door sags. Ball bearings eliminate that friction at the pivot point. The two ball bearing races in the TABB31 carry the door load smoothly, which means quieter operation, longer hinge life, and no sag on standard weight doors receiving average daily use. That's why ball bearing hinges are the default spec for commercial applications while plain bearing hinges are reserved for light-duty or infrequent-use openings.
Cal-Royal TABB31 Technical Specifications
Size: 4-1/2" x 4-1/2". Hinge type: full mortise, both leaves mortised. Knuckles: 5-knuckle. Weight class: standard weight. Gauge: 0.134". Corner: square. Bearings: two ball bearings. Material: wrought steel base. Template: ANSI A156.7 templated hole pattern. Included fasteners: machine screws and wood screws. Sold as: box of 3. UL Listed: yes, for use on fire-rated door assemblies. Meets Buy American Act. BHMA Certified. Logo: stamped with CRP logo (use "UN" prefix when ordering for logo-free version). Brass base material available, use "SB" prefix before part number. ANSI compliance: A156.1 (Butts and Hinges), A156.7 (Template Hinge Dimensions), A156.17 (Self Closing Hinges and Pivots), A156.18 (Materials and Finishes).
Full Mortise Mounting: What It Means for Your Application
Full mortise means both leaves are recessed into the door edge and the door frame. This is the correct mounting type for hollow metal doors in hollow metal frames and wood doors in wood frames. It provides the strongest mechanical attachment and the cleanest finished appearance. The TABB31 is not a half mortise, half surface, or full surface hinge. Confirm your door and frame construction before ordering. For hollow metal doors with channel iron frames, a half surface hinge is the correct configuration.
Standard Weight vs. Heavy Weight: Choosing Correctly
Standard weight hinges like the TABB31 are specified for interior commercial doors receiving average daily use. For high-frequency openings like main building entrances, corridor doors in schools and hospitals, or any door receiving heavy daily traffic, a heavy weight ball bearing hinge is the appropriate upgrade. Heavy weight hinges have a heavier gauge, beveled inner edges that conform to the barrel shape for tighter joints, and machine screws with half screws. If there's any doubt on a high-traffic opening, specify heavy weight. Upgrading a hinge after installation costs far more than the price difference at the time of order.
Available Finishes and NRP Option
The TABB31 is available in a full range of ANSI/BHMA A156.18 architectural finishes: US26D Satin Chrome, US32D Satin Stainless Steel (order as BB31 US32D), US10B Oil Rubbed Bronze, US3 Bright Brass, US4 Satin Brass, US1 Polished Brass, US26 Bright Chrome, and USP Primed for Paint. Stainless steel base material provides true corrosion resistance for exterior-adjacent or high-humidity environments. A Non-Removable Pin (NRP) version is available for security-sensitive openings where pin removal would allow the door to be lifted off the frame from the hinge side. For five-knuckle ball bearing hinge options across additional sizes and configurations, browse our full hinge category.
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