Example of Turret Lathe Work.—The diagrams [Figs. 2] and [3] show a turret lathe operation which is typical in many respects. The part to be turned is a hub casting for an automobile and it is machined in two series of operations. The first series is shown by the plan view, [Fig. 2]. The casting A is held in a three-jaw chuck B. Tool No. 1 on the cross-slide is equipped with two cutters and rough faces the flange and end, while the inner and outer surfaces of the cylindrical part are rough bored and turned by combination boring and turning tool No. 2. This tool has, in addition to a regular boring-bar, a bracket or tool-holder which projects above the work and carries cutters that operate on the top surface. Tools Nos. 3 and 4 next come into action, No. 3 finishing the surfaces roughed out by No. 2, and No. 4 finish-facing the flange and end of the hub. The detailed side view of Tool No. 3 (which is practically the same as No. 2), shows the arrangement of the cutters C and D, one of which turns the cylindrical surface and the other bevels the end of the hub. The hole in the hub is next finished by tool No. 5 which is a stepped reamer that machines the bore and counterbore to the required size within very close limits. The surfaces machined by the different tools referred to are indicated by the sectional view E of the hub, which shows by the numbers what tools are used on each surface.
For the second series of operations, the position of the hub is reversed and it is held in a spring or collet type of chuck as shown by the plan view [Fig. 3]. The finished cylindrical end of the hub is inserted in the split collet F which is drawn back into the tapering collet ring by rod G (operated by turnstile H, [Fig. 1]) thus closing the collet tightly around the casting. The first operation is that of facing the side of the flange and end of the hub with tool No. 6 on the cross-slide, which is shown in the working position. A broad cutter H is used for facing the flange and finishing the large fillet, and the end is faced by a smaller cutter I. When these tools are withdrawn, tool No. 7 is moved up for rough turning the outside of the cylindrical end (preparatory to cutting a thread) and rough boring the hole. These same surfaces are then finished by tool No. 8. The arrangement of tools Nos. 7 and 8 is shown by the detailed view. Tool J turns the part to be threaded; tool K turns the end beyond the threaded part; and tool L bevels the corner or edge. The reaming tool No. 9 is next indexed to the working position for finishing the hole and beveling the outer edge slightly. At the same time, the form tool No. 10, held at the rear of the cross-slide, is fed up for beveling the flange to an angle of 60 degrees. The final operation is that of threading the end, which is done with die No. 11. The boring-bars of tools Nos. 2, 3, 7 and 8 are all provided with pilots N which enter close fitting bushings held in the spindle, to steady the bar while taking the cut. This is a common method of supporting turret lathe tools.
The feed of the turret for both the first and second series of operations is 1/27 inch per revolution and the speeds 60 revolutions per minute for the roughing cuts and 90 revolutions per minute for the finishing cuts. The total time for machining one of these castings complete is about 71/2 minutes, which includes the time required for placing the work in the chuck.
Fig. 4. First Cycle of Operations in Finishing Gasoline Engine
Flywheels on a Pond Turret Lathe
Machining Flywheels in Turret Lathe.—[Figs. 4] to [6], inclusive,illustrate how a gasoline engine flywheel is finished all over in two cycles of operations. First the flywheel is turned complete on one side, the hole bored and reamed, and the outside of the rim finished; in the second cycle the other side of the flywheel is completed.
During the first operation, the work is held by the inside of the rim by means of a four-jaw chuck equipped with hard jaws. The side of the rim, the tapering circumference of the recess, the web, and the hub are first rough-turned, using tools held in the carriage toolpost. The hole is then rough-bored by bar C, which is supported in a bushing in the chuck, as shown in [Fig. 4.] The outside of the wheel rim is rough-turned at the same time by a cutter held in the extension turret tool-holder T ([Fig. 5]), and the taper fit on the inside of the flywheel is turned by means of cutter A ([Fig. 4]) held in a tool-holder attached to the turret.
