Fig. 121.
But the form of template for the flank should be such as shown in [Fig. 121], the curve p representing, and being of the same radius as the pitch circle, and the curve f being that of the hypocycloid. Both these templates are set to the pitch circles and to coincide with the marks made on the wheel teeth to denote the thickness, and with a hardened steel point a line is traced on the tooth showing the correct curve for the same.
Fig. 122.
An experienced hand will find no difficulty in producing true templates by this method, but to avoid all possibility of the segments slipping on coarse pitches, and with large segments, the segments may be connected, as shown in [Fig. 122], in which o represents a strip of steel fastened at one end into one segment and at the other end to the other segment. Sometimes, indeed, where great accuracy is requisite, two pieces of steel are thus employed, the second one being shown at p p, in the figure. The surfaces of these pieces should exactly coincide with the edge of the segments.
Fig. 123.