The sheet-metal worker's guide : a practical handbook for tinsmiths, coppersmiths, zincworkers, etc., comprising numerous geometrical diagrams and working patterns, with descriptive text (1888)
Crane, W. J. E. (W. J. Eden) · London : Lockwood and Son · leaf 57
46 ANGLES. circle of thin brass and divide it into 180 equal parts we form a protractor (Fig 38), or instrument for measuring angles in drawings, &c. Let a b Fig. 37 be the base line, from which ascends a line c e. If we apply the lower straight edge of the instru- … c Fig. 38. ment to the former line, and bring the small nick or mark in the centre of its straight side to c, we shall find that the line e d c cuts the circum-
Sheet-metal work
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