A practical course in mechanical drawing for individual study and shop classes, trade and high schools (1912)
Willard, William Franklin, 1879- · Chicago : Popular mechanics company · leaf 54
Fig. 48. The con-struction for this common object may be derived fromExercise 46 and the figure. The sewing-machine bob-bin-winder is one of several applications of its use. Exercise 48,—The involute spiral. This curve isdeveloped by unwinding a string wrapped about a MECHANICAL DRAWING 51… … Fig:. 49 the third, three, etc. Draw the curve through thepoints. Fig. 49. The involute is used in defining the tooth curve of agear wheel. Exercise ^9—Helix. Fig. 50. A definition of ahelix may be given as the combined vertical and hori-
Mechanical drawing
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