FROM THE LEVEL TO THE RAKE--_continued_.
The plan, elevation and falling line, and position of risers in this
case are the same as in Plate XVII., but show a different way of
getting out the wreaths. This may not be such a correct method as the
former one, as the centre joint will be vertical instead of square to
the tangent across the well as was the case there, but nothing could
be more simple than the method here described. Having the plan and
elevation drawn, square out a bevel line from C, to cut the springing
in R. Make R F equal E D, Fig. 1; say the joint is to be at S on the
right, join S F, draw the joint S P square to the straight rail, and
draw S N square to the tangent F E S.
Fig. 3 shows the face mould. Draw S E D C at right angles, make S E D
equal S E F, Fig. 2, and C D equal C D, Fig. 1. To complete the mould,
make O N and C N equal E R and F R, Fig. 2. Draw V L through O N; make
C R and P H equal C R and R H, Fig. 1. As will be seen, the straight
rail is not in a line with the tangent, and as the joint must be square
to the straight rail it cannot be square to the face of the plank.
Therefore, the face mould for the top side will require to be a trifle
longer, while the mould for the bottom side must be the same distance
shorter. To find out how much the joint will require to be bevelled,
mark off along S N, Fig. 2, S J to equal half thickness of plank; then
the distance between the two lines S P and S N at J is what the joint
will be out of square to face of plank through half its thickness.
The shank of top face mould must be increased, and that of the bottom
reduced to this amount as shown by the shaded parts. The face mould
shown at Fig. 3, being for the under side, is reduced.
Fig. 5 shows the application of the face moulds; as there is no bevel
on the shank E S the joint will only be out of square to face of plank
and not to the tangent. Fig. 6 shows the bottom half; this having no
twist can be struck with the compasses, the same as the plan. It must
be the distance C H, Fig. 2, thicker than the rail. The shaded part
shows how the superfluous stuff must be taken off top and bottom.
Fig. 7 shows the pair in position after being squared.
[Illustration: PLATE 20.]