Bit-Braces. The well-made wooden brace, which for a long time ornamented the walls of the cabinet-maker's shop, has disappeared, and the lighter and more convenient iron brace is used in its stead. A simple form of iron brace is represented by Fig. 119. To insert a bit, grasp the sleeve A and, holding it firmly, turn the brace out by using the other hand on B. When the jaws, C, are opened sufficiently to admit the bit shank, put it in place, reverse the motion of the hand on B, and the bit will be fastened.

Fig. 119

A ratchet brace is shown by Fig. 120. Its office is to turn the bit forward while the brace itself, instead of making a complete revolution, has only a forward and backward movement. As represented by the section AB, the frame c is fastened to the body of the brace of which it becomes a part, d is a spindle which terminates in the socket e, and f is a ratchet-wheel, which is fastened to d. On each side of the ratchet-wheel there is a pawl which, when free to move in response to the action of a spring, engages the notches in the ratchet-wheel f. With the pawls thus engaged, the brace may be used in precisely the same way as the one already described. But, by turning the ring g, one of the pawls is disengaged, and the other acting alone will move the spindle d only when the brace is moving in one direction, the pawl simply slipping over the notches of the ratchet-wheel when the motion is reversed. In this way, a bit may be driven to any depth although each movement of the brace may be less than half of a complete turn. By a proper movement of the ring g, the motion of the bit may be reversed.

Fig. 120

Section A B.

(Enlarged)

The ratchet-brace is useful in boring holes near walls, or in corners where it is impossible to turn a common brace.

The size of any brace is indicated by its "swing," that is, by the diameter of the circle described by B, Fig. 119. The better class are nickel-plated, and are thereby prevented from rusting.

95. A "Universal, Angular, Bit-Stock," such as is represented by Fig. 121, is, for many purposes, more useful than the ratchet-brace. The bit is inserted at A, and a common brace is applied at C. The mechanical arrangement of the parts is such, that, when the brace turns the spindle C, the part A which holds the bit is also turned, notwithstanding the inclination of one part to the other.1 Compared with the ratchet-brace, this has the advantage of producing a continuous motion of the bit. By its use a hole may be bored in the corner as easily as in the middle of a room.

Fig. 121

The angle of the joint may be changed from that shown to one of 180 degrees, by an adjustment at D.