Hinging is the art of connecting two pieces of metal, wood, or other material together, such as a door to its frame; the connecting ligaments that allow one or other of the attached substances to revolve are termed hinges. There are many sorts of hinges, among which may be mentioned, butts, chest hinges, coach hinges, rising hinges, casement hinges, garnets, scuttle hinges, desk hinges, screw hinges, back-fold hinges, centre-point hinges, and so on. To form the hinge of a highly-finished snuff-box requires great mechanical skill; but few of the best jewellers can place a faultless hinge in a snuff-box.

There are many varieties of hinges, and hence there are many modes of applying them, and much dexterity and delicacy are frequently required. In some cases the hinge is visible, in others it is necessary that it should be concealed. Some hinges require not only that the one hinged part should revolve on the other, but that the movable part shall be thrown back to a greater or lesser distance. Figs. 518 to 564 exhibit a great variety of methods of hinging.

Fig. 518 shows the hinging of a door to open to a right angle, as in Fig. 519. Figs. 520, 521, and Figs. 522, 523, show modes of hinging doors to open to an angle of 90°. Figs. 524, 525, show a manner of hinging a door to open at right angles, and to have the hinge concealed. The segments are described from the centre of the hinge A, and light portion requires to be cut out to permit the passage of the leaf of the hinge A B.

Figs. 526, 527, illustrate an example of a centre-pin hinge, the door opening either way, and folding back against the wall in either direction. Draw E F at right angles to the door, and just clearing the line of the wall, which represents the plane in which the inner face of the door will lie when folded back against the wall in either direction. Bisect E F in B; draw A B perpendicular to E F, which make equal to E B or B F then A is the position of the centre of the hinge.

To find the centre of the hinge, Figs. 528, 529; draw A D, making an angle of 45° with the inner edge of the door, and A B parallel to the jamb, meeting D A in A the centre of the hinge; the door, in this case, will move through a quadrant D C.

Figs. 532, 533, are of another variety of centre-pin hinging, opening through a quadrant. The distance of A from BC is equal to half B C. In this, as in a previous case, there is a space between the door and the wall when the door is folded back. In Figs. 528, 529, as well as in Figs. 532, 533, there is no space left between the door and the wall.

Fig. 530; bisect the angle at D by the line D A; draw E C and make CF = 3/2 DE; draw F G at right angles to C E, and bisect the angle G F C by the line B F, meeting D A in A; then A is the centre of the hinge. Fig. 531 shows, when the door, Fig. 530, is folded back, that the point C falls on the continuation of the line G F.

Figs. 534, 535; Figs. 536, 537; Figs. 538, 539; and Figs. 540, 541, are examples of centre-pin joints, and require no particular or detailed describing.

Figs. 542 to 544 are of a hinge, the flap of which has a bead B closing into a corresponding hollow, so that the joint cannot be seen through.

Figs. 545 to 547 show a hinge b a let equally into the styles, the knuckles of which form a part of the bead on the edge of the style B. In this case the beads on each side are equal and opposite to each other, with the joint-pin in the centre.

In the example, Figs. 548 to 550, the knuckle of the hinge forms a portion of the bead on the style C, and is equal and opposite to the bead of the style D. In Figs. 551 to 553, the beads are not directly opposite to one another.

Fig. 554 exhibits the hinging of a back flap when the centre of the hinge is in the middle of the joint.

Figs. 555, 556, relate to the manner of hinging a back flap when it is necessary to throw the flap back from the joint. An example of a rule-joint is given, Figs. 557, 558.

Figs. 559, 560, point out or define the ordinary mode of hinging shutters to sash-frames.

Figs. 561, 562, illustrate a method of hinging employed when the flap on being opened has to be at a distance from the style. This method of hinging is used on the doors of pews, to throw the opening flap or door clear of the mouldings.

Figs. 563, 564, show the manner of finding the rebate when the hinge is placed on the contrary side. Let h be the centre of the hinge, y e the line of joint on the same side, ac the line of joint on the opposite side, and ec the total depth of the rebate. Bisect ec in d, and join d h; on d h describe a semicircle cutting y e in f, and through f and d draw f b, cutting a c in b, and join a b, bf, and f y, to complete the joint.