Johnston, Philip Devereux, 1855- · New York, D. Williams Company · leaf 72
6 A … F13.3.. Tij.^. 68 A MANUAL OF MECHANICAL DRAWING. CHAPTER VII. Various Curves. Plate 15. Spirals.Fig. 21.—To drazv an approximate spiral from twocentres: Draw centre line A B, and on it mark the centres 1 and 2, whose distance apart shall be equal to one-halfthe distance between the turns of the…
Mechanical drawing
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