Machine tool

“ A good example of a machine-tool is the Drilling Machine, which is used for drilling holes in metal. Such a machine is represented in Fig. 31, where A is the strong framing, which is cast in a single piece, in order to render it as rigid as possible. ”

“ In a milling machine the cut is carried continuously from its commencement to its end, whereas in a shaping or planing machine the tool does not usually cut during the back or return stroke. In either of these machines, therefore, the operator’s skill is required as much in measuring the work, setting the tools feeds, &c., as in shaping the tools, whereas in the milling machine all the skill required lies in the chucking and adjustment of the work to the cutter, rather than in operating the machine, which may therefore be operated by comparatively unskilled labor. ”

“ There were neither planing, slotting, nor shaping machines, and with the exception of very imperfect lathes and a few drills, the preparatory operations of construction were effected entirely by the hands of the workmen. Now, everything is done by machine tools, with a degree of accuracy which the unaided hand could never accomplish. The automaton, or self-acting, machine tool has within itself an almost creative power; in fact, so great are its powers of adaptation, that there is no operation of the human hand that it does not imitate. ”

“ Such machines as are used in shaping materials in the construction of the parts of other machines, and also many of those which perform work, such as boring, planing, riveting, etc., formerly only done by hand, and still performed manually to a greater or less extent, are nearly always called machine tools; the term, engine tool, is more in accord with general usage when referring to large and complicated machines. ”

“ The general types of machine tools seem to be firmly established, and new or startling inventions and revolutionary changes seem unlikely. The present trend is toward higher speeds, heavier cuts with the use of great quantities of lubricant, further refinements of jigs and holding devices, and the use of highly developed automatic machines which may be operated by unskilled labor. ”

“ As the sizes of planing machines increase, they are given increased tool-carrying heads; thus, Fig. 1562 represents a class in which two sliding heads are used, so that two cutting tools may operate simultaneously. Each head, however, is capable of independent operation; hence, one tool may be actuated automatically along the cross slide to plane the surfaces of the work, while the other may be used to carry a cut down the sides of the work, or one tool may take the roughing and the other follow with the finishing cut, thus doubling the capacity of the machine. ”

“ It is true that the professionals in machine-making have done much to smooth the path of the amateur. Some of the semi-automatic and automatic machines are so wonderful that one might imagine them endowed with life and professional skill themselves. I have watched, fascinated, the work of a screw-making machine which, after turning the tiny thread, reached over a steel finger and thumb, picked up the screw, lifted it back to a new position and jammed it there for another tool to slide forward at the precisely right second and cut out the cross-nick on the screw-head. ”

“ This is necessary when the spindle of the machine in which it is used has play in the bearings, which is very often the case with boring and drilling machines. The use of g is to act as a guide fixed in the table upon which the work is held, to prevent the tool from springing away from the cut, and hence enabling it to do much smoother work. ”

“ Hundreds of others, however, as managers, superintendents, chief draftsmen and tool makers, have perhaps done more to spread throughout the country the methods and standards of accuracy which have made American machine tools what they are. ”

“ Although the development of modern machinery is largely concerned with motor and transmitting mechanisms, it is to the working machine we must look in order to get a clear idea of the differences between machines and tools. A tool may be quite simple in form and action as a knife, a needle, a saw, a roller, a hammer, or it may embody more complex thought in its construction, more variety in its movement, and call for the play of higher human [46] skill. Such tools or implements are the hand-loom, the lathe, the potter's-wheel. To these tools man stands in a double relation. ”

“ But the profound influence which machine tools have had in that development is scarcely realized, even by tool builders themselves.
Three elements came into industrial life during the latter part of the eighteenth century. ”

“ 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. ”

“ Tool Holders for Planing Machines.—The advantages of tool holders for planing machines are equally as great as those already described for lathes, but as applied to planing machines there is the additional advantage that the clearance necessary on the tool is less variable for planer work than for lathe work, because in lathe work the diameter of the work as well as the rate of tool feed affects the tool clearance, whereas in planer work the tool feed is put on before the tool begins its cutting action ”

“ The T-slots in the table are furnished to standard size, and are at right angles, so that the attachments will be held exactly parallel with, or at a right angle, as the case may be, to the live spindle of the machine; hence the machine will accomplish all the varied results required in the tool room or for machine work generally. ”

“ In single-pointed tools, such as are used upon lathe work, this has but little significance, because it is the work of but a minute or two to grind up the tool to a full point again, but in taps and solid dies, or in chasers in heads (as in some bolt-cutting machines) it is highly important, because it impairs the fit of the threads, and it is difficult to bring the tools to shape after they are once worn. ”

“ If under certain conditions the hand tool does not operate to advantage, these conditions may be varied by a simple movement of the hands, altering the height of the tool to the work, the angle of the cutting edges to the work, or the rate of feed, as the case may be, and instantly perceiving the effects; whereas with tools held by mechanical means, such alterations would involve the expenditure of considerable time in loosening, packing, and fastening the tool, and adjusting it to position. ”

“ Fig. 2017 represents Brown & Sharpe’s grinding machine. The bed, the table, and the cross-feed motion of this machine closely resemble those of the planing machine, but its work is far more smoothly and accurately done than can be performed in a planing machine. The table traverses to and fro, accurately guided in ways, and the revolving emery wheel takes the place of the ordinary cutting tool, being carried in a sliding head upon a cross slide or cross bar. The drum for driving the emery wheel is at the back of the machine, as shown in the cut. ”

“ Any one of the thousand iron planing machines of the country, if put in good condition and set upon the ordinary wood floors, may be made to plane work winding in either direction by shifting a moving load of a few hundred pounds on the floor from one corner of the machine to the other, and the ways of the ordinary turning lathe may be more easily distorted still. Machine tool builders do not believe this, simply because they have not tried it. ”

“ The head stock could be arranged to hold work-pieces, milling cutters or drills. Hardened tools for the necessary cutting operations could be fabricated by the machine from carbon steel in the annealed condition, then tempered, drawn, and sharpened by a separate simpler machine including a small furnace and a tool grinding wheel equipped with tool-holder and feeds. By careful standardization of parts, tools, and fixtures, it is conceivable that such a "one-machine shop" could succeed in reproducing itself. ”

“ It is a highly adaptable machine tool for jig work and for making dies. It does the work of a shaper or milling machine and replaces such operations as nibbling, drilling holes to make a cut, and torch cutting. Twenty assorted saws, 3⁄32 to 1⁄2 inches wide; three flat filebands, 1⁄4-inch, 3⁄8-inch, and 1⁄2-inch; and three file guides are standard equipment. The machine is equipped with a 3⁄4-hp, 208-volt, 3-phase, 60-cycle motor.
(2) Toolroom lathe. The 10-inch toolroom lathe (fig. 24) has a 41⁄2-foot bed and 1-inch collet capacity. ”

“ The machine changes the technique in industrial operation so that all-around skillfulness, while unnecessary to any workman, is still demanded of the working force. In order to reap the full advantages of machinery preference is given to workmen in the various processes who display ingenuity in machine attendance and develop a knack which operates a machine tool at its approximate capacity. The skill, formerly the possession of the mechanic which enabled him to perform several operations, is now distributed so that the skill required in each operation is the qualification of special workmen. ”

“ As a result, the surface produced depends for its truth upon the truth of the tool-guiding ways. In the Poole lathe, however, while guideways are necessarily employed to guide the emery wheels in as straight a line as is possible, by means of such guides, the roll [I-197] itself is employed as a corrective agent to eliminate whatever errors may exist in the guide. The rolls come to this machine turned (in the lathe Fig. 730) , and with their journals ground true (on dead centres) . ”

“ A machine, then, may be described as a complex tool with a fixed relation of processes performed by its parts. Even here we cannot profess to have reached a definition which enables us in all cases to nicely discriminate machine from tool. It is easy to admit that a spade is a tool and not a machine, but if a pair of scissors, a lever, or a crane are tools, and are considered as performing single simple processes, and not a number of organically relative processes, we may by a skilfully arranged gradation be led on to include the whole of machinery under tools. ”

“ As a matter of fact a fine machine-tool is more liable than a watch to get out of order through careless handling, and it no more than a watch, can be properly repaired by a bungler. It follows that skill in the use of machine-tools is as essential to a successful mechanical career now, as skill in the use of hand-tools was formerly. ”

“ To the learner, practice with hand tools is especially advantageous, inasmuch as the strain due to the cut is felt by the operator; hence, the effects of alterations in the shape of the tools, its height or position with relation to the work, and also the resistance of the metal to severance, are more readily understood and appreciated than is the case where the tool is held in a slide rest or other mechanical device. ”

“ A tool is usually more simple than a machine; it is generally used with the hand, whilst a machine is frequently moved by animal or steam power. The simpler machines are often merely one or more tools placed in a frame, and acted on by a moving power. ”

“ The advantages of the screw machine are, that the work requires no centring since it is held in a chuck, that forging operations are dispensed with, that any number of pieces may be made of uniform dimensions without any measuring operations save those necessary when adjusting the tool for the first piece, and that it does not require skilled labor to operate the machine after the tools are once set. ”

“ We are able to machine the earth in much the same way as a piece of metal is machined in the machine shop. In fact, the drill, [252] the circular saw, the slotter, and even the milling machine have their counterpart in the excavating machinery of to-day. Of course we cannot expect to find the counterpart of such machines as the lathe, boring mill, and planer, in which the work revolves against the tool, because this planet of ours is rather too big a piece of stock to be placed between lathe centers or to be bolted to a planer bed. ”

“ The simplest application of a principle of mechanics to an every-day hand-tool may convert it into what is called a machine. Take a three-pronged fork—one of the universal tools;—fasten a rope to the end of the handle; put a log under the fork as a fulcrum; and we have a lever, when pulled down by the rope, which will grub up a strongly-rooted large shrub in a few minutes. The labourer has called in a powerful ally. The tool has become a machine. ”

“ There are still other claimants for the merit of having invented the planing machine; among whom may be mentioned more particularly Matthew Murray of Leeds, and Richard Roberts of Manchester. We are informed by Mr. March, the present mayor of Leeds, head of the celebrated tool-manufacturing firm of that town, that when he first went to work at Matthew Murray's, in 1814, a planing machine of his invention was used to plane the circular part or back of the D valve, which he had by that time introduced in the steam-engine. ”

“ As users of these tools we cannot begin to compare with the skilled workman of ancient days. Our progress is shown not in the development of skill, but in the loss of it. We have taken the tool out of the human hand and put it into an inanimate machine. It is only very recently that the tool was delivered to the machine and that act marked the dawn of the present remarkable mechanical era. ”