Descriptive geometry for students in engineering science and architecture; a carefully graded course of instruction . not in the same plane with it. Each point inthe revolving line travels in the circumference of a circle for its locus, the planeof which is at right angles to the axis. This will be noted in Fig. io8, where c,cc is the axis of rotation, and ah. ah is the line revolving. .y points takenin this line revolve in paths which are the circumferences of circles whose planesare horizontal, the axis being vertical, and on joining the elevations of the extremelimits to which these points
Descriptive geometry for students in engineering science and architecture; a carefully graded course of instruction . not in the same plane with it. Each point inthe revolving line travels in the circumference of a circle for its locus, the planeof which is at right angles to the axis. This will be noted in Fig. io8, where c,cc is the axis of rotation, and ah. ah is the line revolving. .y points takenin this line revolve in paths which are the circumferences of circles whose planesare horizontal, the axis being vertical, and on joining the elevations of the extremelimits to which these points move from one side to the other, the freehand cur\-egives the projection of the contour of the surface of revolution generated, namely,the hyperboloid of revolution. The helicoid. or surface of revolution generated by a straight line movingso that any point in it travels in a helicoidal line or helLx, as a spiral, while the 112 DESCRIPTIVE GEOMETRY line is not in the same plane with the axis, but is constantly maintaining the sameattitude in relation to it, is used in the making of screw-threads on bolts, Fig. iio. In projecting screw-threads, the curved edge lines of the threads are thepaths of points in the generating lines of hehcoids, and may be thought of as lines SURFACES OF REVOLUTION, AND THE SCREW THREAD 113 drawn on the surfaces of cylinders or drums. The development of such a cylin-drical surface of a bolt, showing the thread line, would give that line as a straightone, as ac in the Fig. 109. The Hne ab is the length of the circumference of thecircular section, and the distance be represents the pitch or distance travelled inthe direction of the axis during one revolution, ac is the straight line represent-ing the helicoidal line developed as from the surface of a cylinder. These curvedhelicoidal lines may be projected on to the , and in this way a screw-thread isrepresented. As in illustration, in Fig. no, let ABB2 be the triangular section, madeby a plane
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Keywords: ., bookcentury1900, bookdecade1910, bookpublisheretcetc, bookyear191
