The setting out for the pattern is shown in Fig. 244. The bead is first of all allowed for by lengthening the pipes by the distance A B, which is equal to the length C D E measured around the bead. The position of the point G is found by the rule explained in connection with Fig. 239.
F is the middle point of B E. The points G and F are joined together and the length G J made equal to F B; then F H is drawn parallel to G J and made the same length as the arc K L. Now, if H be joined to J, the point W, where it intersects the line F G, will give the centre of gravity of the section shape. The line N M is now drawn in an average position, its length being marked off equal to the outline BK LO. M N is then produced to meet the centre line in T. The pattern is now laid out as that for a cone frustum, the lengths T M and T N being used as the radii, and the length of the arc R S P being made equal to four times the length of the quarter-circle on V M.