Fig. 16. Bullard Vertical Turret Lathe
Turret-lathe Type of Vertical Boring Mill.—The machine illustrated in [Fig. 16] was designed to combine the advantages of the horizontal turret lathe and the vertical boring mill. It is known as a “vertical turret lathe,” but resembles, in many respects, a vertical boring mill. This machine has a turret on the cross-rail the same as many vertical boring mills, and, in addition, a side-head S. The side-head has a vertical feeding movement, and the tool-bar T can be fed horizontally. The tool-bar is also equipped with a four-sided turret for holding turning tools. This arrangement of the tool-heads makes it possible to use two tools simultaneously upon comparatively small work. When both heads are mounted on the cross-rail, as with a double-head boring mill, it is often impossible to machine certain parts to advantage, because one head interferes with the other.
The drive to the table (for the particular machine illustrated) is from a belt pulley at the rear, and fifteen speed changes are available. Five changes are obtained by turning the pilot-wheel A and this series of five speeds is compounded three times by turning lever B. Each spoke of pilot-wheel A indicates a speed which is engaged only when the spoke is in a vertical position, and the three positions for B are indicated, by slots in the disk shown. The number of table revolutions per minute for different positions of pilot-wheel A and lever B are shown by figures seen through whichever slot is at C. There are five rows of figures corresponding to the five spokes of the pilot-wheel and three figures in a row, and the speed is shown by arrows on the sides of the slots. The segment disk containing these figures also serves as an interlocking device which prevents moving more than one speed controlling lever at a time, in order to avoid damaging the driving mechanism.
The feeding movement for each head is independent. Lever D controls the engagement or disengagement of the vertical or cross feeds for the head on the cross-rail. The feed for the side-head is controlled by lever E. When this lever is pushed inward, the entire head feeds vertically, but when it is pulled out, the tool-bar feeds horizontally. These two feeds can be disengaged by placing the lever in a neutral position. The direction of the feeding movement for either head can be reversed by lever R. The amount of feed is varied by feed-wheel F and clutch-rod G. When lever E is in the neutral position, the side-head or tool-bar can be adjusted by the hand-cranks H and I, respectively. The cross-rail head and its turret slide have rapid power traverse movements for making quick adjustments. This rapid traverse is controlled by the key-handles J.
The feed-screws for the vertical head have micrometer dials K for making accurate adjustments. There are also large dials at L which indicate vertical movements of the side head and horizontal movements of the tool slide. All of these dials have small adjustable clips c which are numbered to correspond to numbers on the faces of the respective turrets. These clips or “observation stops” are used in the production of duplicate parts. For example, suppose a tool in face No. 1 for the main turret is set for a given diameter and height of shoulder on a part which is to be duplicated. To obtain the same setting of the tools for the next piece, clips No. 1, on both the vertical feed rod and screw dials, are placed opposite the graduations which are intersected by stationary pointers secured to the cross-rail. The clips are set in this way after the first part has been machined to the required size and before disturbing the final position of the tools. For turning a duplicate part, the tools are simply brought to the same position by turning the feed screws until the clips and stationary pointers again coincide. For setting tools on other faces of either turret, this operation is repeated, except that clips are used bearing numbers corresponding to the turret face in use.
The main turret of this machine has five holes in which are inserted the necessary boring and turning tools, drills or reamers, as may be required. By having all the tools mounted in the turret, they can be quickly and accurately set in the working position. When the turret is indexed from one face to the next, binder lever N is first loosened. The turret then moves forward, away from its seat, thus disengaging the indexing and registering pins which accurately locate it in any one of the five positions. The turret is revolved by turning crank M, one turn of this handle moving the turret 1/5 revolution or from one hole to the next. The side-head turret is turned by loosening lever O. The turret slide can be locked rigidly in any position by lever P and its saddle is clamped to the cross-rail by lever Q. The binder levers for the saddle and toolslide of the side-head are located at U and V, respectively. A slide that does not require feeding movements is locked in order to obtain greater rigidity. To illustrate, if the main tool slide were to feed vertically and not horizontally, it might be advisable to lock the saddle to the cross-rail, while taking the vertical cut.
The vertical slide can be set at an angle for taper turning, and the turret is accurately located over the center of the table for boring or reaming, by a positive center stop. The machine is provided with a brake for stopping the work table quickly, which is operated by lifting the shaft of pilot-wheel A. The side-and cross-rails are a unit and are adjusted together to accommodate work of different heights. This adjustment is effected by power on the particular machine illustrated, and it is controlled by a lever near the left end of the cross-rail. Before making this adjustment, all binder bolts which normally hold the rails rigidly to the machine column must be released, and care should be taken to tighten them after the adjustment is made.
