Hinges, Fig. 233, are made in several forms. The most common are the butt-hinge or butt, the two leaves of which are rectangular, as in a door-hinge; the strap-hinge, the leaves of which are long and strap-shaped; the Tee-hinge, one leaf of which is a butt, and the other strap-shaped; the chest-hinge, one leaf of which is bent at a right angle, used for chest covers; the table-hinge used for folding table tops with a rule joint; the piano-hinge, as long as the joint; the blank hinge or screen-hinge which opens both ways; the stop-hinge, which opens only 90°; and the "hook-and-eye" or "gate" hinge.
|e. Blank or Screen-hinge.|
The knuckle of the hinge is the cylindrical part that connects the two leaves, Fig. 234. The "acorn" is the head of the "pintle" or pin that passes thru the knuckle. Sizes of butts are indicated in inches for length, and as "narrow," "middle," "broad" and "desk" for width. The pin may be either riveted into the knuckle as in box-hinges or removable as in door-butts. Sometimes, as in blind-hinges, the pintle is fastened into one knuckle, but turns freely in the other.
|Fig. 234. Parts of a butt-hinge.|
A butt-hinge may be set in one of three positions, Fig. 235: (1) Where it is desired to have the hinge open as wide as possible, as in a door. Here the knuckle is set well out from the wood. (2) Where it is desired to have the hinged portion open flat and no more. Here the center of the pin is in line with the outside surface of the wood. This is less likely to rack the hinge than the other two positions. (3) Where it is desired to have the knuckle project as little as possible.
Fig. 235. Three Positions of Hinges.