TURNING AND
BORING

By FRANKLIN D. JONES

Associate Editor of MACHINERY
Author of “Planing and Milling”

FIRST EDITION
FIFTH PRINTING

NEW YORK
THE INDUSTRIAL PRESS
London: THE MACHINERY PUBLISHING CO., Ltd.
1919

Copyright, 1914
BY
THE INDUSTRIAL PRESS
NEW YORK

PREFACE

Specialization in machine-tool manufacture has been developed to such a degree that there is need also for treatises which specialize on different classes of tools and their application in modern practice. This book deals exclusively with the use of various types of turning and boring machines and their attachments, and is believed to be unusually complete. In addition to standard practice, it describes many special operations seldom or never presented in text-books. Very little space is given to mere descriptions of different types of machine tools, the principal purpose being to explain the use of the machine and the practical problems connected with its operation, rather than the constructional details. No attempt has been made to describe every machine or tool which might properly be included, but rather to deal with the more important and useful operations, especially those which illustrate general principles.

Readers of mechanical literature are familiar with Machinery's 25-cent Reference Books, of which one hundred and twenty-five different titles have been published during the past six years. Many subjects, however, cannot be adequately covered in all their phases in books of this size, and in response to a demand for more comprehensive and detailed treatments on the more important mechanical subjects, it has been deemed advisable to bring out a number of larger volumes, of which this is one. This work includes much of the material published in Machinery's Reference Books Nos. 91, 92 and 95, together with a great amount of additional information on modern boring and turning methods.

It is a pleasure to acknowledge our indebtedness to the manufacturers who generously supplied illustrations and data, including many interesting operations from actual practice. Much valuable information was also obtained from Machinery.

F. D. J.

New York, May, 1914.

CONTENTS

TURNING AND BORING

CHAPTER I

The standard “engine” lathe, which is the type commonly used by machinists for doing general work, is one of the most important tools in a machine shop, because it is adapted to a great variety of operations, such as turning all sorts of cylindrical and taper parts, boring holes, cutting threads, etc. The illustration Fig. 1 shows a lathe which, in many respects, represents a typical design, and while some of the parts are arranged differently on other makes, the general construction is practically the same as on the machine illustrated.

On the carriage, there is a cross-slide D which can be moved at right angles to the lathe bed by handle e, and on D there is an upper or compound slide E which can be swiveled to different positions. The tool t, that does the turning, is clamped to the upper slide, as shown, and it can be moved with relation to the work by the movement of the carriage C along the bed, or by moving slide D crosswise. The lengthwise movement is used to feed the tool along the work when turning, boring or cutting a screw, and the crosswise movement for facing the ends of shafts, etc., or for radial turning. When the tool is to be fed at an angle, other than at right angles to the bed, slide E, which can be set to the required angle, is used. The lengthwise and crosswise feeding movements can be effected by power, the lengthwise feed being engaged by tightening knob k, and the cross-feed by tightening knob l. The direction of either of these movements can also be reversed by shifting lever r. Ordinarily the carriage and slide are adjusted by hand to bring the tool into the proper position for turning to the required diameter, and then the power feed (operating in the desired direction) is engaged. The tailstock T can be clamped in different positions along the bed, to suit the length of the work, and its center h₁ can be moved in or out for a short distance, when adjusting it to the work, by turning handle n.

As some metals are much harder than others, and as the diameters of parts to be turned also vary considerably, speed changes are necessary, because if the speed is excessive, the turning tool will become dull in too short a time. These speed changes (with a belt-driven lathe) are obtained by placing the driving belt on different steps of cone-pulley P, and also by the use of back-gears. The cone-pulley can be connected directly with the spindle or be disengaged from it by means of bolt m. When the pulley and spindle are connected, five speeds (with this particular lathe) are obtained by simply shifting the driving belt to different steps of the cone. When a slower speed is required than can be obtained with the belt on the largest step of the cone, the latter is disconnected from the spindle, and the back-gears G and G₁ (shown in the plan view Fig. 2) are moved forward into mesh by turning handle O; the drive is then from cone-pulley P and gear L to gear G, and from gear G₁ to the large gear J on the spindle. When driving through the back-gears, five more speed changes are obtained by shifting the position of the driving belt, as before. The fastest speed with the back-gears in mesh is somewhat slower than the slowest speed when driving direct or with the back-gears out of mesh; hence, with this particular lathe, a series of ten gradually increasing speeds is obtained. Changes of feed for the turning tool are also required, and these are obtained by shifting the belt operating on pulleys p and p₁ to different-sized steps. On some lathes these feed changes are obtained through gears which can be shifted to give different ratios. Many lathes also have gears in the headstock for changing the speeds.

Front and rear views of the carriage apron, which contains the feeding mechanism, are shown in Figs. 3 and 4, to indicate how the feeds are engaged and reversed. The feed-rod R (Fig. 1) drives the small bevel gears A and A₁ (Figs. 3 and 4), which are mounted on a slide S that can be moved by lever r to bring either bevel gear into mesh with gear B. Gear B is attached to pinion b (see Fig. 3) meshing with gear C, which, when knob k (Fig. 1) is tightened, is locked by a friction clutch to pinion c. The latter pinion drives gear D which rotates shaft E. A pinion cut on the end of shaft E engages rack K (Fig. 1) attached to the bed, so that the rotation of E (which is controlled by knob k) moves the carriage along the bed. To reverse the direction of the movement, it is only necessary to throw gear A into mesh and gear A₁ out, or vice versa, by operating lever r. When the carriage is traversed by hand, shaft E and gear D are rotated by pinion d₁ connected with handle d (Fig. 1).

The drive for the cross-feed is from gear C to gear F which can be engaged through a friction clutch (operated by knob l, Fig. 1) with gear G meshing with a pinion H. The latter rotates the cross-feed screw, which passes through a nut attached to slide D (Fig. 1), thus moving the latter at right angles to the ways of the bed. The cross-feed is also reversed by means of lever r. As previously explained, lead-screw S is only used for feeding the carriage when cutting threads. The carriage is engaged with this screw by means of two half-nuts N (Fig. 4) that are free to slide vertically and are closed around the screw by operating lever u. These half-nuts can only be closed when lever r is in a central or neutral position, so that the screw feed and the regular turning feed cannot be engaged at the same time. As previously mentioned, lead-screw S, Fig. 1, is rotated from the lathe spindle, through gears a, b and c, called change gears. An assortment of these gears, of various sizes, is provided with the lathe, for cutting screws of different pitch. The gears to use for any pitch within the range of the lathe are given on the plate I.

Example of Cylindrical Turning.—Having now considered the principal features of what might be called a standard lathe, the method of using it in the production of machine parts will be explained. To begin with a simple example of work, suppose a steel shaft is to be turned to a diameter of 2¹/₄ inches and a length of 14¹/₂ inches, these being the finished dimensions. We will assume that the rough stock is cut off to a length of 14⁵/₈ inches and has a diameter of 2⁵/₈ inches. The first step in this operation is to form conically shaped center-holes in each end of the piece as indicated at c in Fig. 5. As all work of this kind is held, while being turned, between the centers h and h₁, holes corresponding in shape to these centers are necessary to keep the work in place. There are several methods of forming these center-holes, as explained later.

After the work is centered, a dog A is clamped to one end by tightening screw s; it is then placed between the centers of the lathe. The dog has a projecting end or “tail,” as it is commonly called, which enters a slot in the faceplate F and thereby drives or rotates the work, when power is applied to the lathe spindle onto which the faceplate is screwed. The tailstock center h₁, after being oiled, should be set up just tight enough to eliminate all play, without interfering with a free rotary movement of the work. This is done by turning handle n, and when the center is properly adjusted, the tailstock spindle containing the center is locked by tightening handle p. (Ordinary machine oil is commonly used for lubricating lathe centers, but a lubricant having more “body” should be used, especially when turning heavy parts. The following mixtures are recommended: 1. Dry or powdered red lead mixed with a good grade of mineral oil to the consistency of cream. 2. White lead mixed with sperm oil with enough graphite added to give the mixture a dark lead color.)