Wallis, Rolland S. [from old catalog], Iowa state college of agriculture and mechanic arts, Ames. Dept. of engineering extension. [from old catalog] · Ames, Iowa, Engineering extension department, Iowa state college · leaf 21
ed protractors. Protractor.—While not the most accurate method of measuring andlavin* out angles, the use of a protractor is one of the most convenient.There are manv types available, ranging from the common semi-circulartvpe (Fio- 20)to precise instruments equipped with verniers, microm- 18 eter… … Fig. 22.—Movable-arm protractor. grave the graduations on the under side so that they are in direct con-tact with the surface of the drawing. Two improved patterns of thesemi-circular type are shown (Fig. 21), as well as a good movable arm
Mechanical drawing
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