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 55 - ... diameter of a gear is the diameter measured at the bottom or roots of the teeth. The center distance is the distance between the centers of two meshing gears, the pitch circles of which are tangent to each other. The diametral pitch of a gear is the number of teeth for each inch of pitch diameter, and is found by dividing the number of teeth by the pitch diameter. The circular pitch is the distance from the center of one tooth to the center of the next along the pitch circle. The chordal pitch...
Page 24 - 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 which he will...
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 30 - ... to avoid interference. In fact, the point of the tooth may be left off altogether, or rounded off. The pinion tooth need not be carried in to the usual root line, but may just clear the truncated tooth of the gear. No correction for interference is needed on the points of the pinion teeth or on the flanks of the gear teeth. Grant's Odontograph Tables for Involute Teeth * • From
Page 38 - ... coins of the same value, and the cycloidal tooth would never be missed if it were 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,' or the natural reluctance of the average human mind to adopt a change, particularly a change for the better.
Page 30 - 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 to the addendum line from centres on the base line. Set the dividers to the tabular flank radius (corrected), and draw in all the flanks from the pitch line to the base line. Draw straight radial flanks from the base line to the root line, and round them into the clearance...
Page 38 - There is no more need of two different kinds of tooth curves for gears of the same pitch than there is need for two different threads for standard screws, or two different coins of the same value, and the cycloidal tooth would never be missed, if it were 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 30 - The point of the tooth may be left off altogether or rounded over to get the appearance of a long tooth. The pinion tooth need not be carried in to the usual root line, but, as in the figure, may just clear the truncated tooth of the gear.
Page 42 - Had. .62 .63 .64 .65 .67 .68 .70 .72 .74 .76 .79 .83 .90 .93 .94 Dis.

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