This section is from the book "Lathe Design, Construction And Operation, With Practical Examples Of The Lathe Work", by Oscar E. Perrigo. Also available from Amazon: Lathe Design: Construction And Operation.
These figures will give a good idea of the substantial design of this device, which was evidently intended for heavy work and hard usage. It is very important that all parts of a turret, of whatever kind of type and for whatever purpose, should be strong, rigid, and well fitted. If not of sufficient weight to give it the necessary strength it will fail when put to the actual test of hard work. If not of sufficient rigidity the tools will "chatter" and either seriously mar or spoil the work. If all the parts are not well fitted the tools will not "line up" with the head-stock spindle, and as a consequence true work cannot be done in the machine. It may be stated as a practical fact that in turrets built by the best manufacturers it is not usual to find the entire six holes lining up perfectly with the head-stock spindle. While the present machines of this type are far ahead of those built a few years ago, in these respects, the practical shop man will be fairly well satisfied with a turret if he finds but two of the holes "dead true," two more near enough true for the usual class of work, and the remaining two considerably out of true. And this will generally be the case even though the "finish boring" of these holes is done with a tool carried by the head-stock spindle in the lathe that the turret is fitted up for. To the young machinist this may seem strange, but it is nevertheless true, and true of probably a large majority of turret machines of the present day.
A very complete turret lathe for working brass and other similar metals is built by the Dreses Machine Tool Company. It is shown in Fig. 302, and is known as a 15-inch friction back geared brass turret lathe, and is provided with a special chuck, cutting-off slide and a slide-rest.
The bed is of the box pattern with a dovetail top, which provides the best means for keeping alignment and for quick and firm gripping of the turret and cut-off rest. It is supported on the three-point principle to avoid springing and getting out of alignment through careless setting up or settling of floors and foundations. The top is provided with holes for the oil and chips to drop through.
The head-stock on the smaller machines is cast in one piece with the bed. In this machine it is attached to the bed by gibs and bolts. The housings are provided for either phosphor bronze or babbitt metal bearings.
Fig. 302. - 15-inch Friction Back Geared Brass Turret Lathe, with Special Chuck, Cutting-off Slide and Slide-Rest, built by the Dreses Machine Tool Company.
The friction clutch back gear is of a new design, very simple in operation and positive in action. The wear is taken up by a screw driver from the outside, without even removing the cover.
The spindle is of special hammered crucible steel. The bearings are ground and run in phosphor bronze boxes with special means for oiling and taking up the wear.
The turret revolves automatically on a ground steel stem with special device for taking up the wear. It is provided with a set-over device. The top slide can be operated either by the crank and screw shown at the rear end, or by the capstan levers in the usual manner. One of the capstan handles is provided with a short handle at right angles with it for convenience in quick operations.
The entire capstan wheel may be removed and a crank substituted when quick operations are constantly required.
The longitudinal and cross-feed stop screws are located in easily accessible places. The base slide is clamped to the bed by a single handle and the operation of clamping is by a single motion.
The turret locking bolt withdraws by the return stroke of the top slide, so that the operator needs only to revolve the turret. This is equally effective as a full automatic turret, but less costly and complicated.
The index ring and key are of hardened steel and ground. The square locking bolt is provided with an adjustable taper gib, and a coil spring for actuating it.
The cutting-off slide is extra heavy and is provided with an independent stop for both front and rear tools. It has both a screw and crank wheel feed and a lever feed, either of which may be used as occasion may require.
The slide-rest is of much better design and construction than is common in similar work and is a very useful addition to the lathe, increasing its capacity in handling work of complicated nature, as by its use another series of cuts may be made without removing the work from the chuck.
The special chuck is so arranged that the work may be gripped or released while the machine is running, thus avoiding the necessity of stopping to feed the bar in every time a piece of work is cut from the bar.
The feed is a positive geared device that should do the work well and efficiently.
Taken altogether the lathe is well designed and has been provided with many very useful devices that no doubt prove convenient and effective in practical work. The special forming slide located next to the turret may, of course, be located at any point in relation to the usual cutting-off slide or the slide-rest that may be desired in order to properly perform the work in hand. Either of these adjuncts may be removed when not required for the piece to be machined, or all may be used upon a long or complicated job when needed.
A combination turret lathe built by the R. K. Le Blond Machine Tool Company is shown in Fig. 303. The head-stock and its appendages are the same as those shown in Fig. 300, and the bed and cabinets supporting it are the same. The turret and carriage arrangements, however, are quite different and adapted to a much larger range of work.
The carriage is fitted with a turret tool-post which will carry four tools under the massive top plate shown, and which are securely fastened by the set-screws through it, thus materially increasing its capacity for different cuts on the same piece of work. A binding lever on its top secures the tool clamp in any desired position.
Fig. 303. - Combination Turret Lathe, built by the R. K. Le Blond Machine Tool Company.