Fig. 2818.
“Draw on a piece of board the line a b, [Fig. 2816], and from any point c mark a semicircle equal in radius to that of the radius of the body of the pattern, draw the line e parallel to a b, and distant from it to an amount equal to the radius of the branch, then from the junction of e with the semicircle as at d, mark the line f at a right angle to a b. Let it now be noted that the semicircle a g represents half the pattern body, and e d f b the branch; hence from f to g is the length of the branch end that will require to be curved to fit the circumference of the body, while it is also the length to be added to the distance the branch requires to stand out from the body. To draw the curve on the end d f g of the branch the gauge or marking instrument, shown in [Fig. 2817], is employed. The branch p is placed in V-blocks ([Fig. 2818]), resting upon a plane surface. The gauge consists of a stand e carrying a vertical bar a; upon a is the closely fitting cross-tube carrying the arm c, which in turn carries the marking pointer d, which is set distant from the centre of the bar a to the amount of the radius of the piece of work or the cylinder is to fit against.
Fig. 2819.
“If the branch required to stand at an angle to the body, as in [Fig. 2819], the marking may be performed by the same gauge and in the same manner, but the axial line of the branch must be set, when marking one side, at an acute angle to the axial line of a, and at an obtuse angle to a when turned over to mark the other side, which may be done in each case by raising one of the V-blocks until the branch lies in either case at the same angle to a as it will require to stand to the body on which it is to fit.
Fig. 2820.