Fig. 1827a.
The construction of the head of this machine is shown in [Fig. 1827a]. z is the live or driving spindle, upon which is fast the head a. In a are pivoted at m the levers l which carry the dies d, which are secured in place in the levers by the set-screws b and adjusted to cut to the required diameter by the screws e. The levers l are closed upon the clutch c by means of the springs r and s, each of these springs acting upon two diametrically opposite levers, hence the action of the springs is to open the dies d. The clutch c has a cone at t and slides endways upon the live spindle z. The clutch lever and shoes are upon a shaft running across the machine and actuated by a rod corresponding to the rod r in [Fig. 1820]. When the clutch and levers l are in the position shown in the figures the dies are closed for threading the bolt, and when this threading has proceeded to the required distance along the work, clutch c is moved by the aforesaid rod and lever in the direction of arrow w, and the springs r, s close the ends p of lever l down upon the body x of the clutch opening the dies and causing the threading to cease.
Fig. 1828.
[Fig. 1828] represents a “double” rapid machine for threading work up to four inches in diameter, and therefore having back gear so as to provide sufficient power. The gauge rod from the carriage here disengages a bell crank from the end of the long lever shown, and thus prevents the spring to operate the cross shaft and open the dies.
