Mechanical drawing. Elementary and advanced (1910)
Reid, John S. (John Simpson), 1856- · New York, J. Wiley & sons; [etc, etc.] · leaf 115
Fig. 137. Fig. 138. draw with the 300 triangle and T-square the V of the threadsintersecting at the points b . . b . . the bottom of the threads. At the point O on line A6 draw two semicircles with radii || the top and bottom of the thread respectively. Divide these into any number of equal parts…
