ng of the tool, owing to the thrust
of the cut, sometimes results in spoiled work, especially when an
attempt is made to turn close to the finished size by taking a heavy
roughing cut. Suppose the end of a cylindrical part is first reduced for
a short distance by taking several trial cuts until the diameter _d_,
Fig. 8, is slightly above the finished size and the power feed is then
engaged. When the tool begins to take the full depth _e_ of the cut, the
point, which ordinarily would be set a little above the center, tends to
spring downward into the work, and if there were considerable springing
action, the part would probably be turned below the finished size, the
increased reduction beginning at the point where the full cut started.

[Illustration: Fig. 7. Threading Tool]

This springing action, as far as the tool is concerned, can be
practically eliminated by locating the tool so that the distance _A_
between the tool-block and cutting end, or the "overhang," is as short
as possible. Even though the tool has little overhang it may tilt
downward because the toolslide is loose on its ways, and for this reason
the slide should have a snug adjustment that will permit an easy
movement without unnecessary play. The toolslides of all lathes are
provided with gibs which can be adjusted by screws to compensate for
wear, or to secure a more rigid bearing.

[Illustration: Fig. 8. To avoid springing, Overhang A of Tool should not
be Excessive]

When roughing cuts are to be taken, the tool should be located so that
any change in its position which might be caused by the pressure of the
cut will not spoil the work. This point is illustrated at _A_ in Fig. 9.
Suppose the end of a rod has been reduced by taking a number of trial
cuts, until it is 1/32 inch above the finished size. If the power feed
is then engaged with the tool clamped in an oblique position, as shown,
when the full cut is encountered at _c_, the tool, unless very tightly
clamped, may be shifted backward by the lateral thrust of the cut, as
indicated by the dotted lines. The point will then begin turning smaller
than the finished size and the work will be spoiled. To prevent any
change of position, it is good practice, especially when roughing, to
clamp the tool square with the surface being turned, or in other words,
at right angles to its direction of movement. Occasionally, however,
there is a decided advantage in having the tool set at an angle. For
example,