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Five Knuckle Ball Bearing
Five Knuckle Ball Bearing commercial hinges are built for smoother, longer-lasting door operation on high-traffic openings, using ball bearings to reduce friction and wear at the knuckles. Shop National Lock Supply for a wide selection of five-knuckle, full-mortise ball bearing hinges in common sizes, materials, finishes, and options like non-removable pins and electrified (wired) models.
Frequently Asked Questions
What are Five Knuckle Ball Bearing hinges?
They’re commercial butt hinges with five knuckles and ball bearings between the knuckles, designed to support heavier doors and frequent cycles with a smoother swing.
Why choose ball bearing hinges instead of plain bearing?
Ball bearings reduce metal-on-metal friction, which helps doors operate more smoothly and can extend hinge life on heavier or frequently used openings.
What does “five knuckle” mean?
The knuckles are the interlocking hinge barrels where the pin runs through; “five knuckle” is a common commercial configuration that accommodates bearing sets and adds stability for higher-duty use.
What is a “full mortise” hinge?
A full mortise hinge means both leaves are mortised—one into the door edge and one into the frame, so the hinge sits flush when the door is closed.
Standard weight vs. heavy weight, how do I choose?
As a rule of thumb, standard-weight models are often recommended for medium-weight doors and moderate cycling, while heavy-weight models are better for heavier doors and high-frequency use. (Many listings call out guidance like <150 lbs vs. >150 lbs and cycling recommendations.)
What sizes are common in this category?
Typical commercial sizes you’ll see include 3-1/2" x 3-1/2", 4-1/2" x 4", 4-1/2" x 4-1/2", 5" x 4-1/2", and 5" x 5" depending on the door/frame prep and duty requirements.
What materials and finishes are available?
Expect common commercial options like steel and stainless steel, with finishes such as US26D (satin chrome) and US32D (satin stainless) to match other architectural hardware.
Do Five Knuckle Ball Bearing hinges come with security options like non-removable pins?
Yes, many lines offer NRP (non-removable pin) variants for outswing/exterior openings where pin removal is a concern.
Are there electrified (wired) options in this category?
Yes, some five-knuckle ball bearing hinges are available with built-in wire transfer (e.g., 4-wire or 8-wire models) to move power/data from frame to door for access control devices.
Are these hinges suitable for fire-rated door assemblies?
They can be, fire door hardware must match the door’s listing and required standards; guidance commonly references hinges that meet ANSI / BHMA A156.1 requirements, and fire openings must follow applicable code/listing criteria. Always verify the specific hinge’s listing and the door label requirements for your opening.