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 20
(a) (b) Fig. 21.—Improved 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…
Mechanical drawing
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