Fig. 1006.
[Figs. 1005] and [1006] show a convenient form of holder, the chaser a being accurately fitted into a recess in the holder d, so that it may be set square in the holder without requiring to be adjusted to come fair with the thread grooves after having been ground to resharpen it. The short chasers are held by the clamp b, which has at c a projection fitting into a recess in the holder to cause the clamp to adjust itself fairly.
Fig. 1007.
Fig. 1008.
In setting a chaser to correct position in a tool post the points of the teeth may be set to the surface of the work as in [Fig. 1007], or if the thread is partly produced and the lathe has a compound slide rest, the tool may be set to the tops of the thread as in [Fig. 1008], and then brought into position to meet the thread grooves by operating the slide rest.
It is obvious that the height and position of a chaser require to be as accurately set as a single-pointed tool, but it is more difficult to set it because it can only be sharpened by grinding the top face, and this alters the height at each grinding.