The most important thing to take notice of in jointing together a cone and pipe is to so arrange them that the elliptic cut on the cone shall be exactly the same shape and size as the cut on the pipe. This is done by imagining that both cone and pipe are tangential to a common sphere. In practice it amounts simply to drawing in a circle, equal to the diameter of the pipe, and then fitting the cone so that its outside lines shall touch the circle. Thus, in Fig. 216 a circle is described from centre, s, having a radius equal to that of the pipe, and then drawing the pipe and cone to touch this in any position, as required. The points where the outside lines of cone and pipe intersect will give the ends, a and 6, of the joint line. This construction should be most carefully gone over, on account of its great importance, it having to be used in all cases where conical and cylindrical pipes are required to be connected together in this way.
The pattern for the round pipe will be set out in the usual manner, lines above the base line being measured off to determine the length of those to the left of the girth line on the pattern
The construction lines for the conical pattern will be obtained in the ordinary way by running radial lines, as shown, and from where these cross the joint line, a 6, drawing lines square to the axis on to the outside of cone. After having set out the pattern for the complete cone the points, 0, 1, 2, etc., are obtained by cutting off the lines, C 0, C 1, etc., equal to c 0, c 1, c 2, etc., from the elevation.
No allowance for connecting pipe and cone is shown, this being put on according to the method of jointing followed.