Fig. 94.
In [Fig. 94] the process is shown carried out for several teeth. On the pitch circle p p, divisions 1, 2, 3, 4, &c., for the thickness of teeth and the width of the spaces are marked. The compasses are set to the radius by the construction shown in [Fig. 93], then from a, the point b on t is marked, and from b the curve c is struck.
In like manner, from d, g, j, the centres e, h, k, wherefrom to strike the respective curves, f, i, l, are obtained.
Then from m the point n, on t t, is marked, giving the centre wherefrom to strike the curve at h m, and from o is obtained the point p, on t t, serving as a centre for the curve e o.
Fig. 95.
A more simple method of finding point f is to make a sheet metal template, c, as in [Fig. 95], its edges being at an angle one to the other of 75° and 30′. One of its edges is marked off in quarters of an inch, as 1, 2, 3, 4, &c. Place one of its edges coincident with the line r, its point touching the pitch circle at the side of a tooth, as at a, and the centre for marking the curve on that side of the tooth will be found on the graduated edge at a distance from a equal to one-fourth the length of r.