Fig. 988.
Fig. 989.
Fig. 990.
To facilitate grinding the tools to a correct angle, the gauge shown in [Fig. 988] is employed, the various notches being for the pitches of thread for which they are respectively marked, but, the edge of the gauge being circular, does not afford much guide to the eye in grinding the angles equal from the sides of the body of the tool; hence the form of gauge shown in [Fig. 989] is preferable, because the tool can be so ground that the edge of the gauge stands parallel with the side of the tool steel, so that the tool will, when in correct position, point straight to the work axis. To insure correctness in setting the tool, it may then be set with a square s in [Fig. 990], held firmly with its back against the side of the tool, which may be adjusted in the tool post until the blade b comes fair with the work.