. 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. . horizontal screw passage, or nut, to receive the screw spindle,I, which is held by an eye at the end of the socket groove,and is actuated by means of a button on tlic outside. By 190 THE PRACTICAL DRAUGHTSMANS turning the screw, i, in either direction, the centre leg may beadjusted with great accuracy at any part of the socket. Inadjusting the instrument to any measurement, the pencil socket,M, is loosened,
. 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. . horizontal screw passage, or nut, to receive the screw spindle,I, which is held by an eye at the end of the socket groove,and is actuated by means of a button on tlic outside. By 190 THE PRACTICAL DRAUGHTSMANS turning the screw, i, in either direction, the centre leg may beadjusted with great accuracy at any part of the socket. Inadjusting the instrument to any measurement, the pencil socket,M, is loosened, and set pretty near the mark, and fixed; theexact length of radius is then obtained by adjusting the centre legby means of the screw. A pair of beam compasses, or dividers, ofsomewhat different description, are represented in side elevation infig. 25. In tliis instrument, which is entirely of metal, the centre Fig. 3g is fixed to the bar, and the moveable leg iscarried by a socket entirely embracing the bar,and sliding upon it. An additional socket iscarried by the bar, and is connected to the firstby a longitudinal screw spindle, whilst it maybe fixed at any point on the bar by means ofa pinching screw underneath. The bar is graduated, and in thelarger socket an opening is made having a bevilled edge, uponwhich a vernier scale is cut, so that very minute measurementsmay be taken. In setting the instrument, the smaller socket isfixed at a convenient point on the bar and then the larger socket,which carries the moveable point, pencil, or pen, is set back orforward, as necessary, by the longitudinal screw connecting it tothe smaller socket. Of the compasses class of drawing-instruments, there now re-main to be described the proportional dividers. This instru-ment is represented, in front and side elevation, in figs. 26 and use is to increase or reduce measurements to a different scaleto tha
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Keywords: ., bo, bookcentury1800, bookdecade1850, booksubjectmechanicaldrawing
