Gear tooth

“ On the other hand the teeth of the two wheels may be of such numbers that those on one wheel will not fall into gear with the same teeth on the other except at intervals, and thus an inequality on any one tooth is subjected to correction by all the teeth in the other wheel. When a tooth is added to the number of teeth on a wheel to effect this purpose it is termed a hunting cog, or hunting tooth, because if one wheel have a tooth less, then any two teeth which meet in the first revolution are distant, one tooth in the second, two teeth in the third, three in the fourth, and so on. ”

“ The names given to the various lines of a tooth on a gear-wheel are as follows:
In Figure 233, A is the face and B the flank of a tooth, while C is the point, and D the root of the tooth; E is the height or depth, and F the breadth. P P is the pitch circle, and the space between the two teeth, as H, is termed a space. ”

“ Cut one or more spaces and measure the teeth at both large and small ends, either with a gear tooth vernier or with gauges made from thin pieces of metal and having a slot cut to give the correct depth and width at the pitch line.
If the teeth at the large end are too thick when the small end is correct, the amount to set the table out of centre must be increased. On the other hand, if the small end is too thick when the large end is ”

“ There is, indeed, good authority for believing that this type of gear, which is a modification of Lloyd’s pin-roller gear as used on the quadrant in England, may become a popular one. Grant, the well-known authority on gears, says: “The pin gear is particularly valuable when the pins are made in the form of rollers, for then the minimum of friction is reached, the friction between the tooth and pin, otherwise a sliding friction at a line bearing is, with a roller-pin, a rolling friction. When properly made there is no form of tooth that is superior to the pin tooth.” ”

“ It is made of a piece of brass, 1⁄8 in. thick and about 5 in. long, shaped as shown, forming a tooth, A, according to the size of the teeth required in the gear wheel, with the end B on a radial line from the center of the wheel. Use one or more hacksaws, according to the size of the slots or teeth to be cut. If one blade is not large enough and two are too large, grind off the teeth on the inner side of the saws, or if two are not large enough, place a thin piece of paper or metal between them to make the thickness required. ”

“ Moore’s patent differential epicycloidal gear. The pinion and wheel are loose on the shaft and eccentric. One wheel has one tooth more than the other.
1546. Multiplying bevil gear. A is a fixed wheel, the cross C is keyed to shaft, B loose on ditto, D and E loose on C; then B is driven at a speed greater than the shaft in proportion to the diameters of the gear. See Patent No. 12,696, 1884.
1547. Double worm gear, right and left hand threads. Neutralises the end thrust on shaft. A and B may be geared together.
1548. Pointed gear; used for light work and for minimum of friction. ”

“ In determining the strength of cut gear-teeth we may suppose the weight to be disposed along the face at the extreme height of the tooth, in which case the theoretical shape of the tooth to possess equal strength at every point from the addendum circle to the root would be a parabola, as shown by the dotted lines in Fig. ”

“ It is under these conditions, which mainly occur in high velocities with one of the wheels having cast teeth, that mortise wheels, or cogging, is employed, possessing the advantage that a broken or worn-out tooth, or teeth, may be readily replaced. It is usual, however, to assign to wooden teeth a value of strength more nearly equal to that of its strength in proportion to that of cast iron ”

“ Let us imagine that some workman has, at some previous time, put in a new cylinder, and instead of putting in one of the proper size he has put one in too large or too small. Now, in either case he would have to remove a portion of the escape-wheel tooth, that is, shorten the tooth: because, if the cylinder was too large it would not go in between the teeth, and consequently the teeth would have to be cut or stoned away. If the cylinder was too small, again the teeth would have to be cut away to allow them to enter the cylinder. ”

“ We divide the circle n n, representing the periphery of our escape wheel, into fifteen spaces, to represent teeth, commencing at f and continued as shown at o o until the entire wheel is divided. We only show four teeth complete, but the same methods as produced these will produce them all. To briefly recapitulate the instructions for drawing the teeth for the ratchet-tooth lever escapement: We draw the face of the teeth at an angle of twenty-four degrees to a radial line; the back of the tooth at an angle of thirty-six degrees to the same radial line ”

“ The Liberty makers have brought out a sprocket with a change in the form of the teeth which is so slight that it hardly shows in a cut and is not even noticed on the bicycle itself at a careless glance. The change consists in cutting down most of the teeth in height and thickness, so that only each fifth tooth acts in the driving, the intermediate teeth serving only as guides to keep the chain in track. ”

“ At each machine sat a human being working with hand, foot, and eye, watching the flashing needle, guarding the margin of the seams, jerking the cloth hither and thither quickly, accurately, watching the spool to see that the thread ran freely, oiling the gear with one hand while the other continued to push the garment rapidly under the needle, the whole body swaying, bending, twisting this way and that to keep time and pace with the work. ”

“ As the grinding circle is so much larger than the blank, any error here is greatly reduced in the finished wheel. Once in a punch mark the nail must not be allowed to slip until the tooth has been cut.
In practice, it will be found better, after each stroke of the handle, to give a quarter turn outward to the screw G, thus avoiding the scraping of the tool on the up stroke. The cutter can be made of any suitable steel with the cutting point ground to give whatever [425] shape is desired for the tooth. The best shape for any particular purpose can be found by reference to a book on gears. ”

“ As useful an instrument as any for their removal is a curved elevator (fig. 49) , the blade of which can often be inserted under the crown, and assuming that good leverage is thus obtained, the tooth can be prised up. Sometimes the tooth is firmly embedded in the bone. In such cases a clear view of the tooth may be obtained by gradually packing the soft tissues apart, the periosteum covering the alveolus should then be raised, and the bone surrounding the tooth cut away with suitable instruments. The tooth, when freely exposed, should be removed with an elevator or forceps. ”

“ Note.—The teeth of spur wheels cast from a pattern must of necessity be larger at one side than at the other, because the teeth must have taper to permit the extraction of the pattern from the mould; therefore, in fixing wheels to gear, the large side of one should meet the smaller side of the other; should the two large sides come together the teeth will meet only at the large side, and the teeth will probably break away from the excessive strain on that point. ”

“ The ordinary practice is to first set the tool the same as for cutting a thread. The motion of the toolslide is then adjusted so that the tool on the forward stroke will meet the front of each tooth, and start back as soon as the tool leaves the end of the land or top of the tooth. ”

“ In Shoa, the practice of surgery directs the removal of a carious tooth with the hammer, punch, and pincers of the blacksmith. Should venesection be required, a stick placed in the patient’s mouth is tightened by means of a thong passed round his neck, and the distended veins of the forehead are then opened with a razor. Cupping, performed by means of a horn exhausted by suction, is also extremely fashionable; and actual cautery, which is believed to strengthen the muscles of the spear arm, is applied by means either of a pile of lighted cotton, or a stick heated by rapid friction. ”

“ When the tooth is even, or nearly so, with the others on each side of it, the best instrument will be the hawk’s-bill forceps, of very small size, and with narrow blades. The instrument being fixed as low on the neck of the tooth as possible, a gentle but firm movement is to be made forwards, so as just to separate the organ from the back part of the alveolar cavity, and then, continuously with this motion, the tooth is at once to be raised out of the socket. ”

“ Instruments.—The instruments in general use for the removal of teeth are forceps and elevators. The Forceps is an amplified pair of pincers or pliers. It is made up of three parts, namely, the blades or portions beyond the joint which are applied to the tooth, the joint itself, and the handles. Forceps should be made of fine steel, should be light and yet strong enough to withstand without bending any strain that may be put upon them. [1] The blades should be shaped to fit the tooth they are intended to remove, and they should be clear of the crown when applied. ”

“ The cutter thus formed produces, when passed through the wheel once, and to the required depth, a tooth of one curve from end to end, having its thickness and width of space correct at the smaller face diameter only, the teeth being too thick and the spaces too narrow as the outer diameter of the wheel is approached. ”

“ As the teeth of cast wheels are, from their deviation from accuracy in the tooth curves and the concentricity of the teeth to the wheel centre, apt to create noise in running, it is not unusual to cast one or both wheels with mortises in the rim to receive wooden teeth. ”

“ For illustration, it is often urged that there is a time in the action of the club-tooth lever escapement action when the incline on the tooth and the incline on the pallet present parallel surfaces, and consequently endure excessive friction, especially if the oil is a little thickened. ”

“ The bend or set of the tooth in spring set saws, should not extend more than half way down the depth of the tooth, which will make the set more uniform and save tooth breakage, it being borne in mind, that a tooth hard enough to break if the set extends down to the root, will set easily if it extends half way down only, and that a saw may be soft enough to file, and of a proper temper, and yet break if the spring set is attempted to be carried too far down the tooth. ”

“ I claim, 1st, A tool for opening sheet metal cans, composed of a hand lever, B, carrying a tooth, c, and connected to tongs, A, or other equivalent means, capable of clamping said tooth-carrying lever to the can, as set forth.
2d, Placing the tooth, c, in an oblique direction, when the same is used in combination with the hand lever, B, and clamping device A, substantially as and for the purpose described. ”

“ The first of the seven grinders, which, as I have said, is frequently absent, and, when it does exist, is small in the horse, is a good-sized and permanent tooth, while the grinder which follows it is but little larger than the hinder ones. The crowns of the grinders are short, and, although the fundamental pattern of the horse-tooth is discernible, the front and back ridges are less curved, the accessory pillars are wanting, and the valleys, much shallower, are not filled up with cement. ”