The bolt to be threaded is gripped in the vice l, operated by hand by the hand wheel m, and is moved by hand up to the head d, by the hand wheel q operating the pinion in the rack shown at the back of the machine. When the dies or chasers have cut or threaded the bolt to the required distance, the threading dies are opened automatically as follows:—-
At h is a clutch ring for opening and closing the threading chasers, and at n is the lever operating the shoes in the groove of the clutch ring. This lever is upon a shaft running across the machine and having at its end the catch piece p; at z is a catch for holding p upright against the pressure of a spring that is beneath the bed of the machine, and presses on an arm on the same shaft as the catch piece p. On the back jaw of the vice l is a bracket carrying a rod r, and the bolt or work is threaded until the end of rod r lifts catch z, when the before-mentioned spring pulls lever n and clutch ring h forward, opening the dies and therefore stopping the threading operation. The length of thread cut upon the work is obviously determined by adjusting the distance rod r projects through v. The handle w is upon the same shaft as catch piece p and clutch lever n, and therefore affords means of opening the dies by hand.
The operation of the machine obviously consists of gripping the work in vice l, moving it up to the head d by the hand wheel q, setting the rod r to open the dies when the bolt is threaded to the required length, and moving the vice back to receive a subsequent piece of work.
The construction of the head d and clutch and ring h is shown in [Figs. 1821] and [1822].
Fig. 1821.
Fig. 1822.