Fig. 101. Finding Angle between Tangents
for Squaring Joints of Ramped Wreath.
The face-mould, as here presented, will further help toward an understanding of the layout of face-moulds as shown in Figs. [96] and [97]. It will be observed that the pitch of the bottom rail is continued from a″ to b″, a condition caused by the necessity of jointing the wreath to the end of the straight rail at a″, the joint being made square to both the straight rail and the bottom tangent a″. From b″ a line is drawn to d″, which is a fixed point determined by the number of risers in the well-hole. From point d″, the level tangent d″ 5 is drawn in line with the level rail of the landing; thus the pitch-line of the tangents over the well-hole is found, and, as was shown in the explanation of [Fig. 95], the tangents as here presented will be those required on the face-mould to square the joints of the wreath.
In [Fig. 98] the tangents of the face-mould for the bottom wreath are shown to be a″ and b″. To place tangent a″ in position on the face-mould, it is revolved, as shown by the arc, to m, cutting a line previously drawn from w square to the tangent b″ extended. Then, by connecting m to b″, the bottom tangent is placed in position on the face-mould. The joint at m is to be made square to it; and the joint at c, the other end of the mould, is to be made square to the tangent b″.
Fig. 102. Bottom Steps with Obtuse-Angle Plan.
