Origin of the screw thread. Ancient boring tools. Suggestions of the screw form. The “Worm Gimlet.” Making the first nuts. An old device for cutting threads in wood. Archimedes and his helical device for raising water. Jacques Berson’s French lathe. Joseph Moxan’s English lathes. The French lathe of 1772. John Maudsley’s English lathes. Maudsley’s slide-rest. Another French lathes. The use of a “master screw.” A form of slide-rest. An old-time worm and worm-gear. Simple method of developing the screw thread. Anthon Robinson’s triple-threaded screw. The many uses of the early lathes. An old “chain lathe.” Its detailed construction. Cutting left-hand threads. Crown gear and “lantern pinion” for operating the lead screw. Transition from wooden to iron lathe beds. The Putman lathe of 1836. The Freeland lathe of 1853. Various classes of lathes to be illustrated and described.
THE origin of the screw thread, or the threaded screw, reaches so far back into ancient times that it is impossible to determine when, where, or by whom it was first conceived or used. That it was known in one form or another as far back as the use of iron for tools is altogether probable. Holes must have been made in wood by some kind of an iron instrument which was the predecessor of the gimlet. This instrument was most likely square or of some form nearly approaching that. In order to be at all effective, it must have had sharp corners.
As the straight-edged sharp knife was first accidentally and then purposely hacked into notches and became the first saw, so may the corners of the early boring instruments have had notches formed in them to facilitate their action upon the material to be bored. These notches may have been gradually deepened for the same purpose, with the idea that the deeper they were the more useful they would become. We can very readily conceive that in making these notches the tool was laid on its side and gradually revolved as the notches were made, beginning at the point and working upwards as the tool was revolved. This of itself would have a natural tendency to produce a semblance of a screw thread, which would increase the efficiency of the tool by drawing it into the wood to be bored. When this tendency was noticed it was also natural to see why it acted in this manner and to increase this action by more carefully making these notches. In time, the “worm gimlet” was undoubtedly evolved.
The form of a screw thread having once been arrived at, the realization of its usefulness for various purposes was only a question of time. It is altogether probable, however, that for the purpose of holding parts of a machine together, or for similar mechanical purpose, screws were first made of wood. It is also pretty certain that they were first made in a very crude form without much regard to the exactness of the pitch or form of the thread, although the V-thread would be the most natural because the simplest form. It is also generally conceded, of course, that they were made by hand and probably with the rude knives then used, as hand tools were the only ones in use.
As to the methods used in making the first nuts for use with the screws, it is probable that they were quite thin as compared with the pitch of the thread, possibly containing but two or three complete revolutions of the thread, which was worked out by sharp-pointed instruments, as the point of the knife or by similar means. This method may have led to the insertion of a metal tooth in a wooden screw and the cutting of the thread in the nut in this manner. We do know for a certainty that a somewhat similar means was used many years later, as the author saw a device such as is represented in Fig. Screw Threading or Tapping Device for Wood , which was preserved as a curiosity, representing the early mechanical method of doing this work.
This device consisted of a turned and threaded screw D, of very hard wood, having one end turned down to a diameter equal to that at the bottom of the thread, while the opposite end was made much larger and contained a hole for passing a bar or lever by means of which it was rotated. At the termination of the thread and beginning of the smaller straight portion the thread was cut away, leaving an abrupt termination, and at this point was inserted a tooth of steel formed in a rough manner to the shape of the thread.
In a wooden nut A a thread had already been cut, by some manner unknown, and through this the screw D was fitted. The piece B, to be tapped or threaded, was clamped to this by means of the steel clamps E, E, binding the two firmly together. To all appearances the tooth or cutter d could be set in or out so as to cut merely a trace of the thread the first time through, then another deeper cut, and finally finished to the full depth. The author had no means of ascertaining the origin of the device, but the wood of which it was composed was black with age and the man who possessed it could not tell how many years his father had owned it or where he got it. It was certain, however, that both of them had been mechanics who had made and repaired the old-time wooden spinning-wheels in which a wooden screw about one inch in diameter had been used for tightening the round band by which the twisting mechanism was operated.
Archimedes, the most celebrated of the ancient mathematicians, certainly had a good idea of the screw thread, as is shown in his famous screw made of a pipe wound helically around a rotating cylinder with which he raised water fully two hundred years before the Christian era. Still it was doubtless a long time after this period before the screw was constructed so as to be applicable to the uses of the present day. Of the progress and development of this and other similar mechanical matters in these early times we have little authentic information. The development of such simple machines as the lathe preceded much that was mechanically important, and to its influence we owe a great deal of the early advancement in the mechanic arts.
We know that a Frenchman by the name of Jacques Berson, in 1569, built a lathe that seems to have been capable of cutting threads on wood. An engraving of his lathe is given in Fig. Berson’s French Lathe, built in 1569. As will be seen in this engraving it was a large, clumsy and cumbersome affair, considering the work it was designed to perform. While the various parts of the machine are not very clearly shown, enough is given to show us that he had a wooden lead screw to give the pitch of the thread by means of a half nut which appears to have been fixed in a wooden frame, to which in turn the piece to be threaded was attached by being journaled or pivoted upon it. The lead screw and the piece to be threaded were both revolved by means of cords wound around spools or drums upon a shaft overhead, and held taut by weights instead of the flexible spring pole already described. These cords were fastened to a vertically sliding frame, also balanced by cords and weights, and to which was attached a sort of stirrup adapted to the foot, by which the machine was operated.
Considering the early time at which this lathe wras constructed, it shows a good deal of ingenuity and may well have been the forerunner of the developments in this line which came after it.
It is a matter of record that in 1680 a mechanic by the name of Joseph Moxan built lathes in England and sold them to other mechanics, but we do not possess any certain or authentic knowledge of their design, as to whether or not screw threads could be cut with them or whether they were designed for work on wood or metals, or both. In all probability they were foot lathes and used on all materials that had been formed in a lathe up to that time.
In the year 1772 the French encyclopedia contained the illustration of a lathe which was provided with a crude arrangement of a tool block or device for holding a lathe tool and adapting it to travel in line with the lathe centers. By this it would seem that the inventor had some idea of the slide rest as it was known at a later day by its invention in a practical form by John Maudsley in England, in the year 1794. Whether Maudsley had seen or heard of the invention shown in the French encyclopedia or not, it would seem fair to assume that he must have seen that or something akin to it, as the twenty-two years elapsing between the one date and the other must have served to make the earlier invention comparatively well known in the two nearby countries, both of which contained, even at this early day, many mechanics. It is interesting to observe that the slide rest invented by Maudsley over a hundred years ago has been so little changed by all the improvements since made in this class of machinery.
There seems to have been an early rivalry between the French and English mechanics in the development of machines and methods for advancing the mechanic arts. The next development of the screw-cutting idea seems to have been of French origin. In this lathe there was an arbor upon which threads of different pitches had been cut. These threads were on short sections of the arbor and by its use the different pitches required could be cut. While the exact manner of using this arbor was not described, its probable method of use will readily suggest itself to the mechanic, and was, no doubt, used at an earlier period, and in fact was what led up to the use of a lead screw or arbor with a multiplicity of different pitches. The principle is analogous to that used in the “Fox” brass finishing lathe so well known and extensively used, not only in finishing plain surfaces but in “chasing threads.”
This machine is shown in Fig. Thread-Cutting Machine using a “Master Screw”, which is a perspective view giving all the essential parts of the mechanism. The head-stock A and tail-stock B are of the usual form in use at the period, and were mounted upon the wooden bed C in the usual manner. The piece D to be threaded, and an equal length of lead screw or ” master screw,” as it was then called, were placed end to end in the lathe, the outer ends held in the lathe centers, and their inner ends, evidently fixed to each other by a clutch of some kind, were supported by a kind of center rest F. Fixed to the front of the bed C was a cast iron supporting bar G, of T-shaped section, extending nearly the entire length of the lathe bed. Upon the bar G, the top of which was of dovetail form, was fitted the carriage H, which was adapted to slide upon it and to support a thread-cutting tool J, and a tool or “leader” K, which fitted into the thread of the ” master screw” E, and served the same purpose as the lead screw nut of the present day. Evidently the operation was that by revolving the piece D the ” master screw” E was also rotated, and this rotation of the threaded screw, acting upon the “leader” K, forced the carriage H forward, causing the thread-cutting tool J to cut a thread upon the piece D, of a pitch equal to that upon the “master screw” E. It is probable that no better means of adjusting the thread-cutting tool J was provided than setting it in by light blows of the hammer. While the threads thus cut were probably rather poor specimens of mechanical work, they answered the requirements of the times, and as usual better means were devised for making them as the need of better and more accurate work created new demands and a higher standard of workmanship.
As will be seen in the above example the idea of the slide-rest is used. In this case some such device was a necessity. Doubtless threads had been cut with some sort of a “chaser,” or tool with notches shaped to the form and pitch of the thread. These were very extensively used later and for many years in brass work, and the old-time machinist was very expert in their use. The slide-rest, as we know it, while it relieved the workman from the fatigue of holding the tool firmly in his hands and depending entirely upon them for the position of the tool, with the exception of such support as the fixed rest gave him, was comparatively slow in coming into general use. While its usefulness must have been apparent to the average mechanic, the conservative ideas then in vogue must have retarded its prompt adoption, as they did many other meritorious inventions.
By the use of the device shown in Fig, Thread-Cutting Machine using a “Master Screw”, it is plain that a different “master screw” was needed for each different pitch of thread to be cut, although the diameter of the work might be anything within the range of the lathe to hold and drive, so that provision was made for supporting the inner ends of the piece to be cut and the ” master screw,” and for driving the latter by the former. The idea of driving the ” master screw ” or lead screw at a different speed from that of the piece to be threaded had not yet been thought of, and it was years before this development took place.
But before proceeding to this phase of the development of thread cutting, and consequently with the further development of the lathe, let us look a little farther into the methods of generating threads. That is, of producing the “master screw,” from which other screws might be made.
The author well remembers during his boyhood an old curiosity shop out in the country in which various kinds of hand machines were made and repaired. Among other things made were various appliances and devices for spinning woolen yarn and reeling it up into skeins of forty threads to a “knot,” as it was called. To furnish an automatic counter for this reel a wormgear of forty teeth was used which engaged with a single threaded worm on the reel-shaft. Both the shaft having the worm formed upon it and the worm-wheel were of wood, usually oak or maple, and the thread was formed by wrapping a piece of paper around the turned shaft and cutting through this with a knife so as to make its length equal to the circumference of the shaft, its width representing the longitudinal distance on the shaft. This piece of paper was then divided into equal parts at each end and inclined lines drawn upon it as shown in Fig. Thread Developed on Paper, the divisions being equal to the pitch of the thread, found by spacing the circumference of the worm-gear blank for the forty teeth. The paper was then glued around the shaft and the diagonal lines gave the correct development of the screw thread, which was worked out with a fine saw, a chisel, or knife, and a triangular file. The teeth of the worm-gear were similarly cut to the proper V-shape, and the result was a perfectly practical and really workmanlike piece of mechanism that answered the purpose remarkably well.
This same method of laying off screw threads was in practical use many years ago and was* used by one Anthony Robinson in England as early as the year 1783, at which time it is recorded of him that he made a triple-threaded screw 6 inches in diameter and 7 feet 6 inches in length. It is said that he first laid off one thread by the method above described, leaving a sufficient space between the convolutions for the other two threads. This first thread was then worked out by hand with the time-honored hammer, chisel, and file, and he afterwards used this thread as a guide for making the other two by the same primitive means.
In the light of the present facilities for cutting threads this process seems most tedious and laborious, and yet much of the machinist’s work of that time was equally slow and must have sorely taxed the patience of the workman, whose principal and often only machine was a lathe of very crude design and workmanship, and in which he managed to do not only turning and boring but slotting, splining, milling, gear-cutting, and an endless variety of similar jobs, and in lieu of a planer having recourse to his ever ready cold chisel, hammer, and file, which with a straight-edge enabled him to make many a flat surface of remarkable nicety considering his limited facilities. And from these pioneer machinist’s came the American machinist of to-day, the most thorough, best educated and expert mechanic the world has ever seen.
It will doubtless have been noticed that in the earlier examples of the lathe, as in most of the machines in use, the framework of the machine in the lathe, the bed, and legs, were made of wood with the various metal parts secured to them. A good example of this method of construction, as well as the general construction of the lathes of the date when this one was built, is shown in front end elevation in Fig. End Elevation of “Chain Lathe”, and in front elevation in Fig. Front Elevation of Old “Chain Lathe”. The history of this lathe is well known to the author, who was well acquainted with the old Scotchman, one John Rea, who had a small machine shop, wood shop, iron foundry, and sawmill in East Beekmantown, Clinton County, New York State, during and for many years prior to the civil war.
This lathe had, as will be seen by an inspection of the drawings, a bed composed of two timbers, placed at the proper distance apart and supported upon wooden legs, which in turn rested upon a cross timber supported by the floor. The timbers were of hard maple, those forming the bed being about 5 inches thick and 12 inches deep and were about 15 feet long. The lathe would swing about 32 inches over the bed. The patterns were made by Mr. Rea, the castings made in his foundry, and the machine work done in the nearby village of Plattsburgh.
The “ways” or V’s of the lathe were of wrought iron about 5/8 x 3 inches let into a “rabbit” cut on the inside edges of the timbers forming the bed, and fastened by large wood screws. The top edges of these iron strips were chipped and filed to an angle of about 45 degrees to the sides, thus making the V an angle of about 90 degrees. The head-stock had cast in it square pockets in which the boxes for the main spindle were fitted by filing, and were held down by a rough wrought iron cap through which passed two threaded iron studs which had been cast into the metal. Upon these were two nuts as shown. The main spindle was of wrought iron and carried a wooden cone pulley built up on cast iron flanges keyed to the spindle. There were no back gears.
The carriage was of the roughest description and had a hand cross feed for the tool block, which carried the old-fashioned tool clamping device held in
place by studs and nuts. The longitudinal hand feed was by means of a crankshaft and pinion with cast teeth and a rack similarly formed, fastened to the front of the bed by wood screws. The longitudinal g power feed was by means g of an ordinary iron chain (hence the common name of ” chain lathe” given to a lathe having this method of feeding). This chain ran over a very clumsy form of sprocket-wheel made somewhat similar to those used in chain hoists of the present day. At the head end of the lathe this sprocket wheel was fixed upon a shaft which carried on its front end a very crude form of a worm-wheel arranged to engage with an equally crude worm upon a shaft journaled in boxes at the front of the bed, one of which was pivoted to the front of the bed and the other capable of sliding vertically and therefore making provision for dropping this worm out of contact with the worm-gear when it was desired to ” throw out the feed.” To keep this feeding mechanism in gear a lever was pivoted upon the front side of the lathe bed, one end connected with the sliding box of the worm-gear shaft and the other hooked under a pin driven into the front of the lathe bed, as shown in the engraving.
This worm-shaft was driven by a round leather belt working in one of the grooves of a three-step cone pulley fixed upon it, and extending up to a similar three-step cone pulley fixed upon the rear end of the main spindle. These pulleys were of hard wood and attached to cast iron flanges fixed in place. The belt was a “homemade” production but very much resembling the best twisted round leather belts of the present day, and was about three quarters of an inch in diameter.
The belt on the cone pulley upon the main spindle was about three and a half inches wide, the large step on the cone being about twenty inches in diameter.
It will be noticed that no provisions was made in this lathe for cutting left-hand threads. It seems altogether probable that the use of left-hand threads began many years after right-hand threads were developed and used, as the need of them no doubt did not exist until the mechanical arts were much farther advanced and possibly not until they were wanted for producing a contrary motion in devices using the worm and worm gear.
The tail-stock was of very simple construction, as will be seen in the engraving, the tail spindle having formed upon its rear end a downwardly projecting arm which embraced a screw tapped into the main casting and being provided with a crank by* which it was operated. To bind the spindle in any desired position a ring was provided, through which the tail spindle passed, and to which was welded a bolt end passing up through the casting and being provided with a lever nut as shown. It will be noticed that by this construction the operation of binding or clamping the tail spindle tended to raise it out of its true bearing position and hold it suspended by this binder and its contact with the top surfaces of the holes through which it passed in the main casting. This continued to be the practice for clamping a tail spindle for many years before the present method of splitting the bearing at the front and fastening it by a clamping screw was first used.
The lead screw was placed at the back of the lathe and had fitted upon it a curved forging, carrying a solid nut and capable of being attached to the carriage by two bolts when it was desired to cut threads. This forging was frequently called a “goose neck,” from its peculiar curved shape. The thread of the lead screws was square and four threads to the inch. It was, of course, made of wrought iron, the use of steel for this purpose being of much later date.
The method of driving the lead screws was characteristic and peculiar and is one of the main reasons for introducing this lathe to the attention of the readers of this book, as it marks one of the first known methods of changing the ratio of speed between the main spindle and the lead screw by means of gears of a varying number of teeth, which is here done in a very crude but comparatively effective .manner. This method was as follows : Upon the rear end of the main spindle was fixed a flange having in its face a series of pins which formed the teeth of a “crown gear” and which engaged with a “lantern pinion” fixed upon an inclined shaft journaled in a bracket fixed to the lathe head and lining with the lead screw. This lantern pinion was made of two heads fitted upon the shaft and having pins running through the heads in a line parallel with the axis of the shaft, similar to the method seen in a brass clock.
Upon the lead screw was a crown wheel similar to that upon the rear end of the main spindle, and whose pins, or teeth, engaged with those formed by the pins or rods in the lantern pinion upon the lower end of the inclined shaft. The fact that this lantern pinion was of much greater length than that on the upper end would seem to indicate that the designer or builder of the lathe had intended to use different sized wheels on the end of the lead screw for the purpose of producing different ratios between the speed of the lead screw and that of the -main spindle, and therefore to cut threads of differing pitches. This seems to have been the earliest method of producing this result by a change of gearing, and probably antedated the method of using differing diameters of spur gears, as it is well known that the crown wheel or pin gear and lantern pinion were the oldest form of gearing, and in use in Egypt at a very early date, and that an imitation of our spur gear was made in a similar manner by inserting the pins in the periphery of the wheel instead of its face. The builder of the lathe in question probably borrowed his idea from some lathes very much older and which he had seen in his native country, as regular spur gearing for the same purpose had been used at a considerably earlier date than the building of his lathe, and as he was a man past middle life at that time. The lathe was built about 1830 and was in active service as late as 1875, although the lantern pinions and pin gears had been discarded and hung up on the walls of the old shop, and in their place were the usual spur gears, and a stud plate had been added for the purpose of carrying an idle gear so as to accommodate different sizes of change gears, and a second idler when left-hand threads were to be cut. Otherwise the old lathe remained as it was originally built.
The transition from wooden to iron beds and legs for lathes was probably made by the early builders of these machines about 1840 or a few years later. It is certain that in 1850 lathes with iron beds were made in New Haven, Conn., and that from this time on iron was universally used for this purpose.
A good example of these lathes built about the time of the change from wood to iron beds is furnished in Fig. Putnam Lathe built in 1836., of one of the lathes built by J. & S. W. Putnam, in Fitchburg, Mass., about the year 1836, or somewhat earlier, and shows in a remarkably sharp contrast with those of the present day when all possible devices are adopted for powerful drives, rapid change gear devices for both feeding and for thread cutting, to the common inch standard and those measured by the metric system; with micrometer gages and stops; with turrets located upon the bed or upon the carriage; and with all manner of attachments and accessories for doing a great and almost endless variety of extremely accurate work, as well as for turning out an immense quantity of it.
One other example of the early lathes is shown that was in some respect somewhat ahead of its time, as will be pointed out. It is a 20-inch swing lathe built by A. M. Freeland, in New York City, in 1853. It is shown in Fig. Freeland Lathe built in 1853. It is said that Mr. Freeland used English machines as his models and was an admirer of Whitworth and his ideals of what machine tools should be. In this lathe the flat-top bed is used as in many English and some very good American lathes at the present time. It will be noticed that the apron is in a somewhat abbreviated form, only sufficient to support its very simple operative mechanism.
The carriage carried a cross-slide upon which were two tool-posts, one in front and one in the rear, which were connected by a right and left cross-feed screw, while there was a short supplemental screw for adjusting the back tool independently of the front one, and also a longitudinal screw for adjusting the tool lengthwise of the work being turned, so that the second or back tool would cut a portion of the feed, as the roughing cut and the front one take the remainder. It will be understood that the back tool is used upside down as in the modern lathes carrying the second tool.
There was no rack and pinion arrangement for lateral hand feed for the carriage, the lead screw being used for this purpose by engaging with its thread a pinion fixed to the shaft operated by the crank at the right-hand end of the apron.
crank at the right-hand end of the apron. It will be noticed that the. driving-cone on the spindle has five steps, as in a modern lathe. The bed seems so light that it would now be called frail, in view of the present duty expected of a lathe of this swing, and in sharp contrast with the massive beds now used.
In future chapters will be shown the modern American lathes with all their peculiar features illustrated, explained, and commented upon as this work progresses, taking up, not only the regular types of engine lathes, but also those of a more special nature such as turret lathes, pattern lathes, bench lathes, high-speed lathes, gap lathes, forming lathes, precision lathes, multiple spindle lathes, and so on, including lathes driven with belts from a counter shaft in the usual manner, and also those driven by electric motors with the most modern appliances.
In illustrating and describing these lathes much care has been exercised to have both the illustration and the description correct as to the facts shown and commented upon, and to this end the builders themselves have furnished the necessary facts so that the statements herein given are from proper authority and may be relied upon in considering the proper selection of the lathe best suited for the work for which it is to be purchased.