hinges

Hinges are mechanical joints that connect two objects allowing relative rotation about a fixed axis. They are used to attach doors, lids, and gates to frames, boxes to lids, and many other applications where a controlled pivot is required. They typically consist of two leaves, a pivot pin, and knuckles that interlock to form a joint; some designs include sleeves or barrels to enclose the pivot.

Common hinge types include butt hinges, which are two rectangular leaves with knuckles; continuous or piano hinges that run the length of the connected edge; concealed hinges, which remain hidden when closed; rising butt hinges that lift the door for clearance; pivot hinges that rotate around a central pivot; and friction or torque hinges designed to hold a position. Hinges vary in material and finish, with steel or stainless steel common for durability, brass for appearance, and aluminum or zinc alloys for light-weight or cost-sensitive applications.

Design considerations include load capacity, door weight and size, clearance and alignment, corrosion resistance, and the need for lubrication. Proper installation requires precise alignment of the hinge axis with the frame and appropriate screw pattern. Hinges are used in doors, cabinets, chests, lids, aircraft compartments, machinery, and other enclosures, and wear or sag can be addressed by replacing pins, screws, or entire hinge sets.