Fig. 1985.
For heads in which the back centre cannot thus be set in line, the form of dog shown in [Fig. 1985] (which is from The American Machinist) may be employed to accommodate the movement of the tail or horns through the driver. Its horn or tail b is made parallel so as to lie flat against the face of the slot in the driver. The other end of tail b is pivoted into a stud whose other end is cylindrical, and passes into a hub provided in one jaw of the dog, the set-screw a being loosened to permit this sliding motion. This locks the horn in the clamp and permits the dog to adjust itself to accommodate the motion endwise that occurs when it is revolved. The amount of this motion obviously depends upon the degree of taper, it being obvious (referring to [Fig. 1982]) that horn d would pass through the chuck, as denoted by the dotted lines, when at the bottom of its path of revolution.
Fig. 1986.
It is obvious that when the head or universal head of the machine is elevated so that it stands vertical, it may have a chuck screwed on and thus possess the capacity of the swiveled vise. It is preferable, however, to have a separate swiveled chuck, such as in [Fig. 1986] (from The American Machinist), which will not stand so high up from the machine bed, and will therefore be more solid and suitable for heavy work.
