usb detected wait download

with the assistance of tee- and set-squares, many of the figures already given can, of course, be easily and quickly constructed ; but, as before observed, the ability to draw them without such aids is absolutely essential, when we consider the calls often made upon the workman for the practical application of such knowledge. As figures, or solids, having more than eight sides or plane surfaces are seldom met with in mechanical construction, and as those we have given include all that form the surfaces of the plane solids intended to be used as objects for projection, we shall now proceed to show how their projections are obtained. CHAPTER VI ORTHOGRAPHIC PROJECTION 16. A CAREFUL study of the preceding chapters, and the solution of the problems contained in the two last, will have prepared the student for entering upon that more important part of our subject viz., "Orthographic Projection," or that special kind of delineation which, when applied to the representation of mechanical subjects, en- ables the engineer or machinist to determine at sight the actual dimen- sions and arrangement of any part of an engine or machine. As, how- ever, a part of a piece of mechanism is but a compound of simple forms made up of what are known as plane solids and solids of revolution alone or combined it is at once manifest that to be able to draw any part of a machine, the would-be draughtsman must first master the delineation of its component parts, and as these resolve themselves into solids, with either plane or curved surfaces, having straight or curved lines for their boundaries, the question of their ultimate accurate representation as a whole becomes one of the correct projection in the