The practical draughtsman's book of industrial design, and machinist's and engineer's drawing companion: forming a complete course of mechanical, engineering, and architectural drawing. (1857)
Armengaud, aîné (Jacques-Eugène), 1810-1891, Armengaud, Charles A., 1813-1893, Amouroux, Jules, Johnson, William, 1823-1864 · New York : Stringer & Townsend · leaf 200
where great accuracy and minuteness is calledfor, it will often be found a very tedious matter to obtain a trueadjustment in this manner, particularly if the joints of the instru-ment are not in perfect working condition. This difficulty is gotover in what are termed spring, or screw bow compasses.… … very small circles, of half or three quarters of an inch in radius atthe most. In the example we have selected for illustration, thecentre leg is of brass, or German silver, and is in one piece withthe milled handle. It is also providedwith a needle point. The pen is madewith a spring-tempered…
Mechanical drawing
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