50. Conical and cylindrical surfaces

To conical are the surfaces formed by moving the rectilinear generatrix l along the curvilinear guide m . The peculiarity of the formation of a conical surface is that

Fig. 95

however, one point of the generator is always fixed. This point is the apex of the conical surface (Fig. 95, a). The determinant of the conical surface includes the vertex S and the guide m, with l '~ S; l '^ m.

Cylindrical include surfaces formed by a direct generator of / moving along a curvilinear guide t parallel to a given direction S (Fig. 95 b). A cylindrical surface can be considered as a special case of a conical surface with an infinitely distant apex S.

The determinant of a cylindrical surface consists of a guide m and a direction S, forming l , with l '|| S; l '^ m.

If the forming cylindrical surface is perpendicular to the plane of the projections, then such a surface is called the projecting one. In fig. 95, a horizontally projecting cylindrical surface is shown.

On cylindrical and conical surfaces, set points are built using generators passing through them. Lines on surfaces, such as line a in fig. 95, in or horizontal h in fig. 95, a, b, are constructed using individual points belonging to these lines.