BBSC77 - 3-1/2 x 3-1/2 BALL BEARING HINGE
BBSC77 3-1/2-Inch Square-Corner Ball Bearing Hinge
Usually Ships: 1-3 Days
Our BBSC77 Ball Bearing Hinge combines a 3-1/2-inch height x 3-1/2-inch open width with .123-inch leaf thickness and square corners. Its standard-weight, two ball bearing, full-mortise construction suits projects specifying this hinge format. Both leaves fit into prepared recesses, one in the door edge and one in the frame.
Practical Uses
- Matching door installations: Use where the door and hardware schedule call for this size and standard-weight bearing arrangement.
- Square-corner replacements: Compare the open size, leaf thickness, mortise, and screw pattern before ordering.
- Hardware refreshes: Coordinate the selected finish with other visible fittings.
- New preparation: Establish matching recesses using the correct BBSC77 drawing and actual supplied hinge.
Everyday example: An installer replaces a worn hinge on an interior door. The existing preparation measures 3-1/2 inches and has square corners, but the installer also checks leaf thickness and attachment before choosing BBSC77. After fitting the complete set, the door is checked for even gaps, free movement, and reliable latching. The .123-inch leaf is a fit detail, not something to assume from nominal height alone.
Dimensions and Preparation
Open size: The 3-1/2-inch width is measured across both leaves with the hinge open, not across a single leaf.
Square corners: Match the leaf outline to both door and frame mortises. A rounded recess may require a different hinge or approved preparation work.
.123-inch leaf thickness: Confirm the actual mortise depth before machining or replacement. The thinner leaves of some residential-weight hinges are not automatically interchangeable with this model.
Full mortise: Both leaves must seat correctly. Aligned hinge axes and sound backing help prevent binding and loose attachment.
Finish Selections
- US10A
- US10B
- US15
- US26
- US26D
- US3
- US32D
- US4
- US5
- USP
Choose the required finish code in the product options. Confirm the exact supplied base material where exposure conditions or a project specification makes that distinction important.
Installation Guidance
- Review the complete door: Check height, width, weight, construction, use frequency, and closer requirements.
- Verify the preparation: Compare the actual hinge with the correct drawing, recess shape, .123-inch depth, and screw positions.
- Support the door: Secure it during removal and fitting so a partially installed set does not carry its weight.
- Check fasteners: The drawing references six #9 x 1-inch wood screws and six #10-24 x 1/2-inch machine screws. Use the appropriate type for the actual preparation and verify adequate engagement.
- Align the set: Seat leaves correctly and keep the hinge axes aligned without forcing the door into position.
- Test operation: Check gaps, free swing, closing, and latching with the complete hardware installed.
Problems It Helps Address
- A matching bearing hinge is needed: Provides two ball bearings in a defined full-mortise format.
- Replacement preparations vary: Identifies square corners, open dimensions, and thickness for comparison.
- Visible finishes need coordination: Offers ten listed finish codes.
Product Details
- Part number: BBSC77
- Open size: 3-1/2 inches high x 3-1/2 inches wide
- Leaf thickness: .123 inch
- Corner style: Square
- Construction: Standard weight, two ball bearing
- Mounting: Full mortise
Care and Project Coordination
Inspect attachment, alignment, and free movement periodically. Use cleaning and lubrication methods appropriate for the supplied finish and bearings. Investigate recurring rubbing or sagging across the complete door and frame rather than expecting hinge replacement alone to correct the cause.
Confirm required hinge quantities and any specified non-removable-pin configuration before ordering. NRP uses a retaining set screw to help prevent pin removal while the door is closed. For rated openings, verify the exact supplied hinge and installation against the complete assembly requirements.
