Fig. 372.
Fig. 373.
The heads from e to i assume various degrees of curve or angle to suit the requirements, but when the other end of the bolt is threaded to receive a nut, some means is necessary to prevent them from rotating in their holes when the nut is screwed up, thus preventing the nut from screwing up sufficiently tight. This is accomplished in woodwork by forging either a square under the head, as in [Fig. 371], or by forging under the head a tit or stop, such as shown in [Figs. 372] and [373] at p. Since, however, forging such stops on the bolt would prevent the heads from being turned up in the lathe, they are for lathe-turned bolts put in after the bolts have been finished in the lathe, a hole being subsequently drilled beneath the head to receive the pin or stop, p, [Fig. 372], which may be tightly driven in. A small slot is cut in the edge of the hole to receive the stop.
Fig. 374.
Bolts are designated for kinds, as in [Fig. 374], in which k is a machine bolt; l a collar bolt, from having a collar on it; m a cotter bolt, from having a cotter or key passing through it to serve in place of a nut; n a carriage bolt, from having a square part under the head to sink in the wood and prevent the bolt from turning with the nut; and o a countersink bolt for cases where the head of the bolt comes flush.
The simple designation “machine bolt” is understood to mean a black or unfinished bolt having a square head and nut, and threaded, when the length of the bolt will admit it, and still leave an unthreaded part under the bolt head, for a length equal to about four times the diameter of the bolt head. If the bolt is to have other than a square head it is still called a machine bolt, but the shape of the head or nut is specially designated as “hexagon head machine bolt,” this naturally implying that a hexagon nut also is required.