Screw

“ Another device for use on lathes specially designed for screw-cutting is shown in Fig. 586, in which a represents the cross feed screw. It is fast to the notched wheel b, and is operated by it in the usual way. c is a short screw which provides journal bearing for the screw a by a plain hole. It is screwed on the outside, and the plate in which it fits acts as its nut. It is fast to the handle d, and is in fact operated by it. ”

“ Screw′-el′evator, a dentist's instrument: a surgeon's instrument for forcing open the jaws; Screw′er.—adj. Screw′ing, exacting: close.—ns. Screw′-jack (same as Jackscrew) ; Screw′-key, a lever for turning the nut of a screw; Screw′-machine′, a machine for making screws; Screw′-nail, a nail made in the form of a screw; Screw′-pile, a pile forced into the ground, and held there by a peculiar kind of screw at the lower extremity; Screw′-pine, a plant of the tropical genus Pandanus, or of the screw-pine family—from the screw-like arrangement of the clustered leaves ”

“ Nevertheless, these threads are made to occupy the same length, in both screw and nut, as though they did enter each other: so that the two parts running parallel to each other, leave a square interstice b, all along both nut and screw: into which balls of brass, or soft iron are [82] introduced, which at once restore the screw-property without it’s friction: a friction so considerable in the common screw, that it always surpasses the effective power, since it remains closed, (in a vice for example) while holding any object squeezed with all the force a man can apply. ”

“ This being turned, operates on the air, as a screw does, and may be literally said to screw the vessel along; the thinness of the medium, and its want of resistance, occasion a loss of much of the force. The screw, I think, would be more effectual if placed below the surface of the water. I very much suspect that a countryman of ours, Mr. Bushnel of Connecticut, is entitled to the merit of a prior discovery of this use of the screw. ”

“ A screw s, having journal bearing in the movable leg, screws through the nut n, and is connected to the upper screw by the chain c, which passes around a chain wheel provided on each screw, so that the movable leg moves in an upright position and the jaw faces stand parallel, no matter what the width of the work. ”

“ To make the teeth of a pair of endless screws fit correctly and work smoothly, a hardened steel screw is made of the figure of the smaller screw, with its thread or threads notched so as to form a cutting tool; the larger screw, or “wheel,” is cast approximately of the required figure; the larger screw and the steel screw are fitted up in their proper relative position, and made to rotate in contact with each other by turning the steel screw, which cuts the threads of the larger screw to their true figure. ”

“ The method of work with the screw is to first rig a brace, and then drill a hole in the safe, cut a thread in the hole and then insert a female screw. Then, with a long steel screw with a handle so long that two men can turn it, the screw is inserted in the female screw, and by turning it goes in until it strikes the back of the safe. ”

“ To the right and left of the screw are beams, with crosspieces fastening them together at both ends. In these crosspieces are holes sheathed with iron, and into them pivots are introduced, and thus the screw is turned by the treading of men. ”

“ The screw is a spiral thread or groove cut round a cylinder, and everywhere making the same angle with the length of it. The force of a power applied to turn a screw round is to the force with which it [297] presses upward, or downward, setting aside the friction, as the distance between two threads is to the circumference where the power is applied; or the advantage gained is as much as the circumference of a circle described by the handle of the winch exceeds the interval, or distance, between the spirals of the screw. Hence the force of any machine turned by a screw can readily be computed ”

“ If a screw rotates, the number of threads which pass a fixed point in one revolution is the number of threads in the screw.
A pair of convex screws, each rotating about its axis, are used as an elementary combination to transmit motion by the sliding contact of their threads. Such screws are commonly called endless screws. At the point of contact of the screws their threads must be parallel; and their line of connexion is the common perpendicular to the acting surfaces of the threads at their point of contact. ”

“ Sometimes we become altogether puzzled and for the moment the action ceases. When I have had occasion to drive a screw in some unusual and inconvenient place, after setting the blade of the screw-driver into the slot I have asked myself, "In which direction does this screw turn?" ”

“ The ordinary screw, cut by dies or in the screw-cutting lathe, is found, on applying comparatively coarse tests, to be far from accurate in pitch, while the thread may be wavy or “ drunken " and the diameter may not be uniform at all points. There are several methods of correcting the errors in screws; the principal one is that of retarding or accelerating the traverse motion of the screw-cutting tool by means of a compensating lever bearing on a compensating bar, which is formed after observations have been made on the degree of accuracy of the leading screw used to propel the tool carriage. ”

“ The mere power of imparting side, or making screws, though valuable enough in itself, falls very far short of ‘power of cue’ as rightly understood. The real meaning of the expression is the ability to combine the 316various elements, such as side, screw, follow, or stab with varying strengths, so as to convert a forcing shot into a soft screw, or a gentle stroke into a fast and fine shot, always with a view to improved position. ”

“ The tailstock or poppet-head screw is a right hand because the nut moves in this case. The object of employing right-hand screws in some cases, and left-hand ones in others, is that it comes most natural in operating a screw to move it from right to left to unscrew, and from left to right to screw up a piece, this being the action of a right-hand screw, left-hand screws being comparatively rarely used in mechanism, save when to attain the object above referred to. ”

“ While the discussion was still going on, one of the distance judges brought in the toe weight, and also the screw which held it, but instead of the screw being broken, or the threads worn, it was seen that the screw had only a head, and very short shank, and that the latter showed marks of its having quite recently had the end of the screw shank filed off, so that there was only a head, and a little bit of shank. ”

“ The threaded extremity of the screw engages a female screw in the loose jaw, and while the same are engaged the screw cannot be released from the embrace of the fixed collar, as it requires considerable lateral movement to accomplish this. ”

“ CHAPTER XVII. ANOTHER WAY OF STRIKING MEDALS WITH THE SCREW. You make an iron frame of similar size & thickness to the one described above, but of sufficient length to enable it to hold not only the two dies, taselli, on which the medal is cut, but also the female [108] screw of bronze. This screw is set beneath the male screw of iron; [109] one ought really to apply the term screw, vite, to this male screw only, the female screw being called chiocciola. The male screw should be three fingers thick and its threads [110] square, because it is stronger thus than of the usual shape. ”

“ The screw is an inclined plane wound round a cylinder; the height of all its revolutions round the cylinder taken together, compared with the space through which the power that turns it passes, is the measure of its mechanical advantage. [27] Let the lever, used in the last experiment, be turned in such a manner as to reach from its gudgeon to the shaft of the Panorganon, guided by an attendant lever as before. (Plate 2. Fig. 8.) ”

“ For example: the parts of a structure have to be forcibly drawn together, a powerful compression has to be exerted, a mass of timber or other material has to be riven asunder by splitting. For purposes of this kind the inclined plane in its various forms, and the screw, are of the greatest use. The screw also, in the form of the screw-jack, is sometimes used in raising weights. It is principally convenient when the weight is enormously great, and the distance through which it has to be raised comparatively small. ”

“ When it is desired to place a screw in a fragile piece of wood that is likely to split, if the screw is heated to a blue color and turned [151] into the wood while hot, there will be scarcely any danger of splitting. ”

“ A screw D, binds the jaws together, and hinders the selvage from going inwards. Upon the side cross beam of the loom, seen in section at I, a bolt is fixed which carries a nut F at its end, into which a screwed iron rod E enters, on one of whose ends is the handle B. The other extremity of the screw E is adapted by a washer and pin to the back of the pincers at the point H, so that by turning the handle to the right or the left, we draw onwards or push backwards the pincers and the stuff at pleasure. The warp of the web is made of black linen yarn. ”

“ No such luck; the screw I had found was the only one. What was it for? Maybe if I removed it I'd find out. But I'd wait until dark to try it. Smale hadn't left a light fixture in the room. After sundown I'd be able to work unobserved.
A couple of hours went by and no one came to disturb my solitude, not even to feed me. I had a short scrap of metal I'd worked loose from my wallet. It was mild steel, flimsy stuff, only about an inch long, but I was hoping the screw might not be set too tight. Aluminum threads strip pretty easily, so it probably wasn't cinched up too hard. ”

“ It is evident, however, that the distance through which the screw can raise a weight must be limited by the length of the screw itself, and that in the length of lift the screw cannot compete with many of the other contrivances used in raising weights. ”

“ Every one of those hundred and fifty thousand screws in every pound is accurately the same as every other, and any and all of them, in this pound or any pound, any one of the millions or ten millions of this size, will fit precisely every hole made for this sized screw in every plate of every watch made in the factory. ”

“ The largest object it will handle is about a half-inch steel screw—"
"Baxter, your brother's accident is connected to that device—and you turn it loose as a novelty!"
"Nonsense. It's safe as a knot-hole. It simply makes things disappear. ”

“ Sketch A shows the two pieces of wood in position, the hole bored in upper piece (only) and countersunk; B shows the screw in position. In this case the screw head is visible. It is occasionally desirable to hide the screw entirely. Sketch C shows the hole prepared for the screw; D shows the screw in position and a circular wooden plug driven in over it. The plug is then leveled with the surface and the screw completely hidden.
Fig. 56. The Difference between Perspective and Mechanical Drawing
27. ”

“ It will not be difficult to trace the resemblance between such an adaptation of the inclined plane and the appearances presented by the thread of a screw: and it may hence be easily understood that a screw is nothing more than an inclined plane constructed upon the surface of a cylinder. ”

“ The thread you wind round the screw has a disappointing way of coming undone, when down falls the bowl, with an escape of sparks. Twisting a piece of paper round the screw is an improvement; but, until you have acquired the knack, the operation has to be renewed every time you relight your pipe. This involves a sad loss of time, and in my case it afforded a butt for the dull wit of visitors. Otherwise I found it satisfactory, and I was soon astonishingly adept at making paper screws. Eventually my briar became as serviceable as formerly, though not, perhaps, so handsome. ”

“ But as the water is not put in motion by the screw without offering some resistance by reason of its inertia, this resistance reacting on the screw operates in the same manner, but not to the same extent, as the wood in the other case. When we know the pitch of the screw, we can calculate what distance the screw would be moved forward in a given number of revolutions if it were working through a solid. ”

“ Any boy who has such a pair of shears, and a paper of screws in his pocket, can build and make to his heart's content, and the happy mother who has this tool on her work-table is done forever with breaking her back over the tool-chest, to find some particularly elusive screw-driver or gimlet. ”

“ A lead screw should preferably be as near as possible to the middle of the lathe shears, and as close to the surface as possible, so as to bring it as nearly in line with the strain on the tool as possible, but on account of the cuttings, which falling upon the screw would cause it to wear rapidly, it is usual to locate it on one side, so as to protect it from the cuttings. ”

“ The screws used by carpenters, smiths, and others, for fastening wood or metal-work together, are generally made by machinery. A piece of wire of the required thickness and length is first cut off, which is then placed in a hole or mould, with its upper orifice “countersunk” as in the annexed cut, and the head of the screw is formed by beating the upper part of the piece of wire into the counter-sinking of the mould. ”