Odontics: Or, The Theory and Practice of the Teeth of Gears

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Lexington gear works, 1891 - Gearing - 103 pages
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Page 83 - CUTTERS. Theoretically, the teeth are of different shapes, as they are in different positions upon the ellipse, and, therefore, each space should be cut with a cutter that is shaped for that particular space. But as this is impracticable, it is necessary to choose the cutter that will serve the best on the average. Strictly, the cutter should be the one that is fitted to cut a spur gear having a pitch radius equal to the radius of curvature of the ellipse at the major apex, but as that cutter will...
Page 15 - THAT PITCH. 36. — THE DIAMETRAL PITCH. This is not a measurement, but a ratio or proportion. It is the number of teeth in the gear divided by the pitch diameter of the gear. Thus, a gear of 48 teeth and 12 inches pitch diameter is of 4 pitch. The advantages of the diametral pitch unit are so apparent TPD TPD TPD TPD 10...
Page 24 - ... service. This cause of deterioration is particularly potent in the case of rough cast teeth, for they can only approximate to the true shape required to transmit a uniform speed, and the continual impact from shocks and rapid variations in the power carried must and does destroy the strength of the metal. There are about as many rules for computing the power of a gear as there are manufacturers of gears, each foundryman having a rule, the only good one, which he has found in some book, and with...
Page 30 - ... profiles on a large scale by the exact method, and then draw the approximate profiles (superimposed), for comparison. Grant's involute Odontograph given below is used as follows: Lay off the pitch circle, addendum, root and clearance lines, as in the preceding case. " Draw the base line one sixtieth of the pitch diameter inside the pitch line. Take the tabular face radius on the dividers, after multiplying or dividing it as required by the table, and draw in all the faces from the pitch line...
Page 43 - The table (Fig. 1354) gives the distances and radii if the pitch is either exactly one diametral or one inch circular, and for any other pitch multiply or divide as directed in the table. FIG.
Page 38 - would be still more clumsy and accurate. There is no more need of two different kinds of tooth curves for gears of the same pitch than there is need of two different kinds of threads for standard screws, or of two different kinds of coins of the same value, and the cycloidal tooth would never be missed if it was dropped altogether. But it was first in the field, is simple in theory, is easily drawn, has the recommendation of many well-meaning teachers, and holds its position by means of "human inertia...
Page 42 - For One Diametral Pitch. For One Inch Circular Pitch. Number of Teeth. For any other pitch divide by that pitch. For any other pitch multiply by that pitch. Faces. Flanks. Faces. Flanks. Exact. Intervals. Rad. Dis. Rad. Dis.
Page 29 - Dra.w the rack tooth by the special method. Teeth. Divide by the Diametral Pitch. Multiply by the Circular Pitch. Face Flank Face Flank Radius. Radius. Radius. Radius. . 10 2.28 .69 .73 .22 11 2.40 .83 .76 .27 12...
Page 30 - ... from a center on the pitch line, and with a radius of 2.10 inches divided by the diametral pitch. .67 inches multiplied by the circular pitch. 64.— DRAFTING INTERNAL GEARS. When the internal gear is to be drawn, the odontograph should be used as if the gear was an ordinary external gear. See Fig. 41. But care must be taken that the tooth of the gear is cut off at the limit line drawn through the interference point i of the pinion.
Page 24 - Journal of the Franklin Institute" for July, 1879. For the single case over twenty different results were obtained, ranging from forty-six to three hundred horse-power, and proving conclusively that the exact object sought is not to be obtained by calculations. "This variety is very convenient, for it is always possible to fit a desired power to a given gear, and if a badly designed gear should break, it is a simple matter to find a rule...

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