Practical draughtsmen's work, with numerous engravings and diagrams (1903)
Hasluck, Paul N. (Paul Nooncree), 1854-1931, ed · Philadelphia, D. McKay · leaf 33
roportional compasses are specially for the purposes of reduc-tion and enlargement. From Fig. 35 it will be seen that the twoarms of the compasses are slotted to receive the sliding blockswhich form the pivot. By means of the milled head shown in thefigure, this pivot can be clamped in any position… … Fig. 35.—Proportional Compasses. pivot is to be set in order to give the required proportion be-tween the openings of the two ends of the instrument. Thus, ifthe line engraved on the sliding centre be set to the line figured 3on the scale, the opening at one end of the compasses will bethree times…
Mechanical drawing
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