Types of Automatic Screw Machines

Manufacturing Auto-Matic Chucking And Turning Machine

Fig. 313 shows a Potter and Johnson machine, called by them a manufacturing automatic chucking and turning machine. It is a good example of a semiautomatic machine which has nearly all the features of the typical automatic screw mchine, and at least one feature that is not adaptable to a machine making the pieces of work from a bar run through the hollow spindle and carrying cutters by which the back of a piece of work held in the chuck is automatically faced. This is accomplished through the lever C, rod D, and cam E.

The headstock is triple-geared so as to provide for ample power for heavy work, this gearing being changed to the desired speeds by a simple lever mechanism. The turret is mounted in the same manner as in a turretlathe, upon a laterally moving slide. This, however, is actuated by suitable connections to the drum cam A, the cam tracks of which are composed of removable plates BB fittingthe surface and attached by screws. The turret has five faces; consequently there are five sets of these plates, which may be so shaped and arranged as to give any length of stroke desired. Usually a full stroke is given to the turret slide, the act of cutting being confined to the latter part of the stroke. The cross-slide is equipped with two tool-postsFF; and the tools can be arranged to work at the same time that the turret tools are cutting-or separately, as the nature of the work may require. The cross-slide may also be provided with tool-blocks for carrying blades or forming tools for special work. It is operated through a rack-and-pinion device from a cam G, and the triangular actuating blocks upon this cam can be adjusted in any required positions around the circle that may be necessary to produce the required movements. The cams A, G, and E are fixed to the same shaft, which makes but one revolution during the cycle of movements necessary to complete one piece of work. This feature is the same in all the different types of this class of machines.