Rubber tapper

“ The advantage of 1⁄16 inch taper lies in the fact that a bolt headed in the ordinary manner can be made to fill the requirements, provided it is made of iron. You may decide that bolts should be tapered, for the reason that when a tapered bolt is driven into its place it can be readily knocked loose, or if that bolt, when in its place, proves to be too loose, you have merely to drive it in a little farther: these are arguments in favor of tapered bolts, showing their advantage. ”

“ An honest firm will add only those materials that will be of service in making the rubber more easy to mould or will improve it in some way. Unfortunately, substances are often added, not for this purpose, but to increase the weight and apparent value of the articles. That is why some rubber overshoes, [12] for instance, wear out so much faster than others.
To make an overshoe, the rubber is run through rollers and formed into thick sheets for soles and thinner sheets for uppers. Another machine coats with gum the cloth used for lining and stays. ”

“ On the other hand, the taper fit is less reliable, because if it loosens, the entire fit is free with but little axial movement. Some lubricant, such as white lead and lard oil mixed to the consistency of paint, should be applied to the pin and bore before assembling, to reduce the tendency of abrasion. ”

“ Boring Tapers with a Boring Bar or Attachment.—In cases where the degree of taper is very great a live centre may be bolted to a chuck plate, as in Fig. 1143, by which means any degree of taper may be bored. Instead of a star feed, a gear feed may be provided by fastening one gear, as a, on the dead centre, and another, as b, on the feed-screw. The cutting tool must stand on the side of the sliding-head—that is, farthest from the line of lathe centres. ”

“ A handy taper gage is shown in Fig. 46. The blades of the gage are made of tool steel. The edge of the blade A is V-shaped, and the blade B has a V-groove to correspond. The end of B is offset so as to make the joint and allow the two blades to be in the same plane. A strong screw and nut are provided to hold the blades at any setting. The user of this gage looks under the edge of A, and is thereby enabled to tell whether the taper coincides with that set by the gage, and also where a taper piece needs touching up to make it true. ”

“ I do not feel disposed to recommend to you any particular taper to be adopted, because it is not a question like that of screw-threads. In screw-threads we throw away the dies that are used upon bolts, which are perishable articles. The taper that has once been adopted in locomotive establishments is a perpetual thing. ”

“ As the commission given to me calls for a decision as to the taper of bolts used in locomotive work, it presupposes that taper bolts are a necessity. In our own practice we divide bolts into several classes, and our rule is that in every case where a through bolt can be used it must be used. If we cannot use a through bolt we use a stud, and where a stud cannot be used we put in a tap bolt, and the reason why a tap bolt comes last is because it is part and parcel of the machine itself. ”

“ The square threads from which elastic webbing is made may be cut from these sheets, though sometimes the sheet is wound on an iron drum, vulcanized by being put into hot water, lightly varnished with shellac to stiffen it, then wound on a wooden cylinder, and cut into square threads. Boiling these in caustic soda removes the shellac. To make round threads, softened rubber is forced through a die. Rubber bands are made by cementing a sheet of rubber into a tube and then cutting them off at whatever width may be desired. Toy balloons are made of such rubber. ”

“ When we adopt a standard for screw-threads, a screw-thread is adopted which has a manifest advantage. A bolt that has one screw thread can be used on any machine. But once having adopted a taper on a road, it is very difficult to make a change; and whether it is wisdom for this Association to say that thus-and-so shall be the standard taper, is a question I am unable to answer. Therefore I am unwilling to present any taper to you, and only present the facts, but will say that 1⁄16 inch is enough. The less taper you have the less material you have to cut away. ”

“ Making Small Taps.—The best manner of making [236] large taps is to turn them to size in a lathe, and then cut the screw by the same means of with a die plate. Small taps cannot very well be so made. A very good way is to get good steel wire—generally sold of all sizes, under the name of Stubs’ steel wire—and from this make taps; the thread can be cut by means of a die stock.
When the thread is properly made, there are several ways to form it so as to make it a cutting tool. One method is to file it with four sides, making it a square. ”

“ If the countersunk head be lengthened so as to take up the whole of the unscrewed part of the bolt, we get the taper bolt shown in fig. 14, which is often used in the couplings of the screw shafts of steamships. The taper bolt has the advantage of having no projecting head, and it may also be made a tight fit in the hole with less trouble than a parallel bolt. Bolts may also have hexagonal heads. ”

“ If, however, one part of the length of a taper turning attachment is much more used than another, it is apt to wear more, which impairs the use of the bar for longer work, as it affects its straightness and causes the slide to be loose in the part most used, and on account of the wear of the sliding block it is proper to wind the tool out from its cut on the back traverse, or otherwise the tool may cut deeper on the back than on the forward traverse, and thus leave a mark on the work surface. ”

“ Referring to the second method, all that is necessary in setting a former or taper attachment bar is to set it out of line with the lathe shears to half the amount of taper that is to be turned, the bar being measured along a length equal to that of the work. Turning tapers with a bar or taper-turning attachment possesses the advantage that the tailstock not being set over, the work centres are not thrown out of line with the live centres, and the latter are not subject to the wear explained with reference to Fig. ”

“ If the length of the work is less than 1 foot, it will be necessary to move the center toward the rear of the machine, and if the length is greater than 1 foot, the adjustment is, of course, in the opposite direction.
The Taper Attachment.—Turning tapers by setting over the tailstock center has some objectionable features. When the lathe centers are not in alignment, as when set for taper turning, they bear unevenly in the work centers because the axis of the work is at an angle with them; this causes the work centers to wear unevenly and results in inaccuracy. ”

“ Half-round taper reamers, such as shown in Fig. 1105, are used for finishing holes. The flat face is cut down, leaving rather more than a half circle; the clearance being filed or ground on the cutting side so as to enable the reamer to cut, and extending from the cutting edge to nearly half-way to the bottom of the reamer.
For holes, however, that are large enough to admit a tool of sufficient strength, the single-pointed boring tool produces the most true work.
Brass finishers use square taper reamers, which produce upon brass more true work than the half-round reamer. ”

“ In the factory the normal vulcanization is carried out in two steps, mixing and curing. The washed sheet india rubber which has not been masticated and which must be perfectly dry is the starting point, and the mixing rolls shown in the cuts are the mechanism for carrying out the first step. These are a pair of powerful rollers which are geared so as to work like ordinary rolls, except that one revolves43 about three times as fast as the other. They are heated by steam, which is introduced inside of them. ”

“ A is the treadle to which the connecting-rod from the machine is fastened by a bolt through the slot at H, or the slot may be in any desirable place. B is a rack in which the end of the lever works, which keeps the treadle bowl steady to the tappet. E is the tappet on the tappet shaft of the loom, and is made so as to act at every shot. D is the fulcrum of the lever, and C is the stand, which is bolted to the ground and fastened to the side of the loom. ”

“ If the proper taper is not attained by blowing, or if ridges are left on the tapered part, the process may be both hastened and improved by giving the taper a preliminary filing with a three-cornered file and kerosene, just as one would proceed with iron or brass. A little filing will often save a good deal of grinding and make a better job. ”

“ Oscillating tappets are situated at one end of a loom, above the crank shaft, from which they are driven by wheel gearing and suitable connecting arms. They are chiefly employed on looms weaving fustians and similar heavy and strong fabrics.
In plain looms with under tappets, the healds are generally connected round a top roller or cone, so that when the tappet is pressing one stave down, it is also taking the other stave up. The shedding is thus positive. For weaving twills, satins, and such weaves, either spring, roller, or pulley top motions are used. ”

“ A very satisfactory one may be made with very little trouble and at slight cost: three feet of inch rubber tubing, a bell-glass, such as is used to shade night tapers, some pieces of cardboard or thin brass, which can be cut with the scissors, and an inch tin elbow, used in speaking-tubes and costing three cents. ”

“ Sometimes a tappet is used to raise the griffes instead of a crank, and of course any required dwell can be made on a tappet; but then it must suit the jacquard, and the greater the dwell, the less time is occupied in the rising and falling of the harness. If the harness is plucked up or dropped down too quickly, the result is a dancing or unsteadiness of the cords, and in a double-lift machine there will be a considerable plucking when the hooks that are rising take up the cords that are falling. ”

“ If a bolt has 5° taper on the side, it may set in place; if it has 7°, it may jump out. That is the angle of friction for iron or other metals. Five degrees would be an absurd angle for a taper bolt. Anything, then, that will hold; that is, if you drive the bolt it will set there.
“This presentation may enable you to arrive at some conclusion. Nothing is more desirable than an interchangeable system. In making turning lathes we try to make all parts interchangeable, and we so fit the sliding spindle. Every sliding spindle in the dead head of the lathe has to be fitted into its own place. ”

“ To try a taper into its place, we either make a chalked stripe along it from end to end, smoothing the chalked surface with the finger, or else apply red marking to it, and then while pressing it firmly into its place, revolve it backwards and forwards, holding it the while firmly to its seat in the hole; we move the longest outwardly projecting end up and down and sideways, carefully noting at which end of the taper there is the most movement. ”

“ The reader will have noticed in the description and will find at once in practice that the press has to be screwed up as the rubber softens. Where heavy iron presses are used the large mass of heated iron comprised in the platen of the press instantly heats the upper surface of the india rubber sheet and the heat immediately penetrates into it, while the heated matrix heats it from below. Thus it softens at once, and the press is directly turned down and the india rubber is driven into the mould and curing at once begins. But where small presses are used this manipulation is not so easy. ”

“ Taps for general use by hand are frequently used to tap holes that do not pass entirely through the work; hence, the taper tap must have a short length of taper so that the second tap may be enabled to carry a full thread as near as possible to the bottom of the hole without carrying so heavy a cut as to render it liable to breakage, and the second or plug tap must in turn have so short a length of its end tapered that it will not throw too much duty upon the bottoming tap. ”

“ To prepare pure gum for the manufacture of sheet rubber and as a starting point for many other preparations, the india rubber is “masticated” in39 special apparatus. The machine consists of a fixed cylinder within which is a corrugated roller set eccentrically and rotated by power. The perfectly dry sheets in the masticator are pressed and rolled and ground and produce a mass of even consistency. Here the welding or cohering action again appears in its fullest development. The perfect dryness of the mass enables it to keep reuniting as fast as divided. ”

“ The ordinary forms of metallic filings coherer of the Branly type require tapping to bring them back to the high resistance or sensitive condition. Lodge arranged a mechanical tapper for the purpose which continually administered the small blow to the tube sufficient to keep the filings in a sensitive condition. Popoff employed an electromagnetic tapper, in fact the mechanism of an electric bell with the gong removed, for this purpose. ”

“ There was no novelty in the combination of a power-operated core with fabric rolls for delivering the rubber impregnated strips through tension rolls to the core, or in the use of pressure rolls to stretch and press the tread at the slow speed of the core followed by the spinning of the stretching or spinning rolls with high speed down the sides from the outer line of the tread to the bead edge of the fabric, or in the use of the tangential force upon the skirts of the fabric to keep them away from the core. ”