Fig. 1933.[31]
[31] [Figs. 1928], [1931], [1932], [1933], are from an article by John J. Grant, in The American Machinist.
Similarly when a groove has been roughed out from the solid, and it is determined to take a finishing cut, the direction of the feed for the latter is of importance. Suppose, for example, a T-groove is to be cut, and that a slot is first cut with a shank cutter as in [Fig. 1931], leaving a light finishing cut of, say, 3⁄64 inch to finish the neck to the dotted lines a b, and entering to within 1⁄16 inch of the full depth as denoted by line c. The enlarged part of the groove may then be cut out, leaving about 3⁄64 inch at the top and bottom, d and e, the cutter having a plain shank (as in [Fig. 1933]), whose diameter should just clear the narrow part of the groove already roughed out. The work will then be ready for the finishing cutter, formed as in [Fig. 1932], whose teeth (on both the shank and the enlarged end) should have a diameter of 3⁄32 less than that of the finished slot. In taking the finishing cut this cutter must be set first to cut the sides b e to finished size, the direction of the feed being such that the pressure of the cut acts to push the cutter back as already explained, and when the cut is finished on this side the finishing cut may be put on the side a d, without traversing the cutter back, or in other words the feed must be carried in the opposite direction, so that the cutter will run under the cut and be pushed back by it, so as to prevent it from running forward as explained with reference to figure.
For ordinary work not requiring great truth, however, the first cutter, [Fig. 1931], may be made of the finished diameter, and be followed by a cutter such as in [Fig. 1933], also of the finished diameter.
Fig. 1934.[32]
Fig. 1935.