The line of separation 5,6 will be more exactly determined as tbllows : Through n draw n 7 parallel to h elating 7; then find only one of the points 5 or 6, say 5; draw 5.7; then 5-6, which is a part of 5-7, is the line of separation.
This face-mould will answer for the upper, as well as the lower half.
The angle l2 1 is the spring of the plank, and is found in the same manner as in solid angles, and having the inter section and cointersection, the face-mould is fo mud as in the seetious of a cylinder. The thee-mould might have been found as in Figure 3, by taking the heights from a line drawn over the thee-mould parallel to A D, Figure I, and laying the plan upwards, as in Figure 3, then proceeding with the operation downwards, as directed in Figure 2 upwards. Or, if the drawing is inverted, the line v 11, Figure 1. will become the base. of the heights, and everythilig else will be in the same position as in Figure 2.
In the application of the moulds. imagine time plank set up to the pitch, and in the Sallie way spring the edge from the under side for the lower piece, and from the nipper side for the upper piece. To apply the moulds to the plank, now sup posed to be sprung or beveled, take the pitch and draw the vertical line, the stock of the bevel being applied to the acute edge of the plank, upwards or downwards, as the case may require : then draw a line equal to the distance of 3-6 from A. 1, upon each plane of the plank parallel to the side ; then the point S being kept to the end of the vertical line, and the side 3-6 upon the parallel line, draw round all the edges of the mould ; turn the moulol to the other side, apply the point S LO the other end of the vortical line, and the part 3.6 upon the line drawn parallel to the thee, and draw round all the edges as betbre ; then cut away the superfluous stuff The sides of the piece intended to form the twist must be perfectly cylindrical, and all the parts so formed, that a straight line or edge may apply to any point, at the same time that it coincides with the surface, and is parallel to the vertical line drawn on the edge of the plank.
The flilling-mould is thus applied : Draw a line upon the ends of the solid piece, at right angles to the vertical sides, from zero at each end, next to the upper side ; then apply the upper edge of the thee-mould next to the top of the plank, and each end to the corresponding end of the piece, bending it so that all parts "nay be in contact with the stuff; then draw a line round all the edges, and it will show the super Ihmus wood to be cut ,11: To construct the face-nould of a hand-rail to a stair upon a level landing, in two parts, round a semicircular newel ; so that when the two pieces are united or fixed in their places, the grain or fibres of the wood will mitre at the joint.
Plate II.—Let Figure I be the rail stretched out, as in the preceding example : draw the chord of the rail, i A., Figure 2, No. 1 ; bisect the end k u at a, and the other end i iv at c; draw j z b c perpendicular to the chord A. i, cutting the con cave and convex sides at z and c ; make z b equal to i c, and E c, Figure 1, equal to w c, Figure 2, No. 1. extended: draw c n, Figure I, perpendicular to A E, cutting the upper edge of the flu at is, and the lower edge at a. ID Figure 2, No. 1, draw' a d perpendicular to A, i, and e e parallel to a d; make a d equal to A B, Figure 1 ; c e, Figure 2, No. 1, equal to E F, Figure! ; and c f, Figure 2, No. 1, equal to c D, Figure 1 ; join a c and d e, Figure 2, No. 1 ; draw f g par allel to a c. cutting d e in y; draw g t parallel to e c, cutting a c in t; join 1 6 ; draw c y parallel to 1 b, cutting the convex side of the plan at y; produce y c to cut the chord k i at 2; draw 2 h parallel to c e; make 2 /1 equal to c e; draw k K parallel to a d; make A. K equal to a d; join //, K ; produce h K and i k to meet each other in 1; draw 1 in parallel to lb: from any point, in, in len, draw en 3 perpendicular to 1 i; produce i I to p, cutting nt 3 at 3; through 3 draw 4 a perpendicular to h 1 ; produce h. 1 to 4 ; make 3 o on p 1 equal to 3-4; joist o ; make 4 a equal to o In, and join a 1: that draw' ordinates on the plan parallel to 1 711, to cut both sides of it, and also the chord k I ; from the intersections in k i, draw lines parallel to c e, to cut It 1 ; from the points of section in 111, draw lines parallel to 1 tr ; make the lines thus drawn parallel to 1 a, equal to the corresponding lines on the plan ; and a curve drawn through these respective points will give the fhce-mould.