the bar forward to the required length. The chuck is operated by levers at the rear of the headstock, which in turn receive their motion from cams carried by the left-hand drum. The bar is fed forward by means of a spring collet which slides forward, carrying the bar with it when the chuck is open, and which slides back upon the bar when the chuck is closed.

The tube carrying this collet is actuated by an adjustable cam on the left-hand cam drum. The cut-off slide, which usually carries a forming tool on the front and a cutting-off tool at the back, is held in its central position by a spring. The tools are operated by levers actuated by cams attached to the disc shown beneath it, the depth of cut being regulated by screws at the upper ends of the levers. The turret slide rotates automatically on the back stroke, and is operated by hard steel cam strips attached to the right-hand cam drum.

The feed motion for actuating the cam shaft is driven from the

counter shaft, and has two speeds, one very much quicker than the other.

The fast speed is used for the idle movements of the machine, such as opening the chuck, feeding the bar forward, withdrawing the tools, rotating the turret, and bringing the tools up to their work, and the slow speed is used for the actual cutting movements of the machine.

The proportions of time during which the cam shaft is rotating fast and slow are governed by adjustable dogs upon the cam disc shown at the extreme right hand of the machine. These dogs can be set to suit the work being done, so that the quick speed comes into operation the instant the cutting tools have completed their operations, thus reducing the time to the minimum.

The spindle is driven by means of gears and high-speed pulleys at the back, and can be driven at two speeds, either forward or reverse, thus enabling the turning operations to be done at high cutting speeds,

and at the same time providing for the slow speeds which are necessary for screwing. Many special adaptations of the machines are made for special work, such as the production of engine studs, condenser ferrules, locomotive-firebox stays, and detached pieces made from castings or forgings, second operations on pieces cut off from the bar, etc.

The number of separate operations which can be performed by machines having standard tools and cams are seven, viz. five turret operations and two cross-slide operations; some of these can be made to do alternative kinds of work, such as turning or boring without altering the cams.

The following is an example of the work which can be done on a machine with standard cam and tools :

:

The chuck opens, and the bar feeds forward to the required length. The bar may be (a) Coned on its end, with the tool in the first turret hole, or it may be centered or centered and faced, on the end. (b) Rough turned with a box tool, fixed in the second turret hole, or drilled, or rough turned and drilled, at the same time with a box tool carrying a drill. (c) Finish turning or reaming, or finish turning and reaming at the same time in third turret hole, using a box tool carrying a reamer. (d) Form with a tool on the front of the cross slide, the work being supported either by a steady bush, carried in the fourth. turret hole, or by a steady peg, as required. (e) Screw with self-opening die; the head is carried in the fifth turret hole. (f) Finally cut off with a tool carried on back of the cross slide.

It will be seen from the above that these operations provide for a great variety of work.

When short pieces of work are required, the turret-slide cam drum and the turret slide can be adjusted into different positions so as to enable them to be brought close up to the chuck, thus enabling short tools to be used, and at the same time providing for the adjustment away from the chuck for doing long pieces.

Tools for Automatic Screw Machine.-A few standard tools are illustrated in Fig. 106 (A, B, C, D, E, F, & G), for straightforward work, such as pins, bolts, screws, and studs.

A represents a starting tool for trueing up and pointing the end of a bar in order to prepare it for the box tool on work of any considerable length.

B is a centering and facing tool used on the end of a bar preparatory to drilling.

C shows an adjustable box tool so arranged that as many as three different diameters may be turned simultaneously; it is also provided with a cutter for finishing the end of the work.

D is a self-opening die head, having four dies which are provided with a roughing and finishing attachment, operated by the lever shown. By means of an adjustable stop contained within the body of the die head, the dies open automatically when the desired length of thread has been cut.

The dies are mounted in sliding jaws, and can quickly be removed for sharpening when necessary.

H

E represents a steady bush and holder for supporting the work while the forming tool is cutting.

The forming tool is shown at F fitted to its holder by means of a dovetailed projection, which gives a very firm grip and also enables the tool to be taken out for grinding and returned with certainty to its correct position.

After finishing, the work is parted from the bar by a cutting-off tool, shown at G.

"Gisholt" Turret Lathe.-Fig. 107 represents a specially powerful turret lathe, designed to cope with a general class of work. As will be

seen, the speed cone is dispensed with, the lathe being fitted with an electric motor. Among other features of this tool are the two saddles to carry the cutting tools; these are constructed with a view to minimize chatter, there being no overhanging parts, and all surfaces being large. The leading saddle carries the tools for operating on external surfaces, and may be traversed further along the bed than is customary in ordinary lathes, to allow the turret saddle to get near the work.

The hexagonal turret will carry six tools, and an intermediate stay is fixed to support boring bars; an additional bearing is obtained in the hollow spindle, thus making a rigid bar of what might otherwise appear to be a slender one. The spindle, which is of large dimensions, carries a universal chuck, which may be driven direct through the spur wheel

shown attached to it. The lathe has a 24-in. swing, and is used for boring, facing, turning, and screw cutting.

Regarding the range of speed of the motor on the machine, the normal speed is about 960 revolutions with a controller that gives a

variation of speed below normal of 50 per cent., and above of 20 per cent., the controller giving nine variations.

The motor used is a 3-H.P., and may be either 110 or 220 volts for

FIG. 107.-"Gisholt " lathe-motor-driven.

the speed given. The turret lathe is made by the Gisholt Machine Co., Madison, Wis., U.S.A., to whom I am indebted for the cut and particulars.

In lathes of this type every conceivable point of advantage appears to have been considered in the design. The bed, which is of box section, extends to the floor, and in this respect is of a most rigid type; there is only one headstock, and it is cast to the bed. The broadnosed tools are operated as easy as the single-pointed tools in a lathe of the ordinary class. A plan of one of these lathes is given in Fig. 108, which explains better than words many of the special features of the lathe.

There is no sparing of surface contact; the carriage is broad, long, and massive, as indeed are all the moving parts. Nothing appears to

come amiss to the tools when several are operating simultaneously; a fact which will be more manifest in the modern lathes directly driven by electric motors, as in Fig. 107. Both the saddle carrying the roughing tools and turret carriage are fitted with independent nuts to engage with the guide screw for screw cutting. Figs. 108, 109, IIO, III show some of the uses to which the lathe may be put. Speed cones (Fig. 109) are commenced by a tool bar with double cutters, which bore and face the three largest steps. The bar is fixed to the face of the turret, and is also supported at the outer end by a bar which fits a bush carried by the chuck. The second and third tools are boring bars for roughing and finishing.

The fourth and fifth tools are standard facing heads, with cutters for boring and facing the largest step. The speed cone is then removed