ht cut
and is intended to finish holes that have been previously bored close to
the required size. Sometimes a flat cutter _C_ is used for roughing and
a reamer for finishing. The reamer is especially desirable for
interchangeable work, when all holes must have a smooth finish and be of
the same diameter. When a reamer is held rigidly to a turret or
toolslide, it is liable to produce a hole that is either tapering or
larger than the reamer diameter. To prevent this, the reamer should be
held in a "floating" holder which, by means of a slight adjustment,
allows the reamer to align itself with the hole. There are several
methods of securing this "floating" movement. (See "Floating Reamer
Holders.")

[Illustration: Fig. 6. Boring with Regular Turning Tools]

Large holes or interior cylindrical surfaces are bored by tools held in
the regular tool-head. The tool is sometimes clamped in a horizontal
position as shown at _A_, Fig. 6, or a bent type is used as at _B_. Cast
iron is usually finished by a broad flat tool as at _C_, the same as
when turning exterior surfaces. Obviously a hole that is bored in this
way must be large enough to admit the tool-block.

[Illustration: Fig. 7. Set of Boring Mill Tools]

=Turning Tools for the Vertical Boring Mill.=--A set of turning tools
for the vertical boring mill is shown in Fig. 7. These tools can be used
for a wide variety of ordinary turning operations. When a great many
duplicate parts are to be machined, special tool equipment can often be
used to advantage, but as the form of this equipment depends upon the
character of the work, only standard tools have been shown in this
illustration. The tool shown at _A_ is a right-hand, roughing tool, and
a left-hand tool of the same type is shown at _B_. Tool _C_ is an offset
or bent, left-hand round nose for roughing, and _D_ is a right-hand
offset roughing tool. A straight round nose is shown at _E_. Tool _F_
has a flat, broad cutting edge and is used for finishing. Left-and
right-hand finishing tools of the offset type are shown at _G_ and _H_,
respectively. Tool _I_ has a square end and is used for cutting grooves.
Right-and left-hand parting tools are shown at _J_ and _K_, and tool _L_
is a form frequently used for rounding corners.

[Illustration: Fig. 8. Diagrams Illustrating Use of Different Forms of
Tools]

The diagrams in Fig. 8 show, in a general way, how each of the tools
illustrated in Fig. 7 are used, and corresponding