The piece of work shown at A in Fig. 3 is an automobile hub, and the tool-holder is arranged so that the operations of turning and boring can be carried on simultaneously with the facing. The tools L, M and N are secured in a special block on the cut-off slide. The tool-holder B is of cast iron and well ribbed; it fits the dovetailed face of the turret, being secured in position by the screws G and the gib F. The turning tools D and E are mounted vertically, and the steel cap-plate C contains the necessary holding screws. The boring-bar H is piloted in a chuck bushing at its forward end and contains the tool J, which stands in a vertical plane like the turning tools. The shank of the bar K is secured by the turret binding screw and an additional set-screw in the holder itself. A tool of this type will produce more accurate work than the type shown in the preceding illustration, on account of the position of the cutting tools with reference to the turret indexing. A feature of some importance is the piloting of the boring-bar, as this assists in the prevention of vibration. Care should be taken in the design of tool-holders of this type, that the overhang from the turret face is not too great, for if this is excessive, a certain amount of chatter is inevitable.

Fig. 3. Multiple Tool-holder for machining Automobile Hubs.