tools are marked by
the same reference letters in both of these illustrations. The right-and
left-hand roughing tools _A_ and _B_ are especially adapted for taking
deep roughing cuts. One feeds away from the center of the table, or to
the right (when held in the right-hand tool-block) and the other tool is
ground to feed in the opposite direction. Ordinarily, when turning plain
flat surfaces, the cut is started at the outside and the tool feeds
toward the center, as at _B_, although it is sometimes more convenient
to feed in the opposite direction, as at _A_, especially when there is a
rim or other projecting part at the outside edge. The tool shown at _A_
could also be used for turning cylindrical surfaces, by clamping it in a
horizontal position across the bottom of the tool-block. The feeding
movement would then be downward or at right-angles to the work table.

The offset round-nose tools _C_ and _D_ are for turning exterior or
interior cylinder surfaces. The shank of this tool is clamped in the
tool-block in a vertical position and as the bent end extends below the
tool-block, it can be fed down close to a shoulder. The straight type
shown at _E_ is commonly used for turning steel or iron, and when the
point is drawn out narrower, it is also used for brass, although the
front is then ground without slope. Tool _F_ is for light finishing cuts
and broad feeds. The amount of feed per revolution of the work should
always be less than the width of the cutting edge as otherwise ridges
will be left on the turned surface. The offset tools _G_ and _H_ are for
finishing exterior and interior cylindrical surfaces. These tools also
have both vertical and horizontal cutting edges and are sometimes used
for first finishing a cylindrical and then a horizontal surface, or
_vice versa_. Tool _I_ is adapted to such work as cutting packing-ring
grooves in engine pistons, forming square or rectangular grooves, and
similar work. The parting tools _J_ and _K_ can also be used for forming
narrow grooves or for cutting off rings, etc. The sketch _K_ (Fig. 8)
indicates how a tool of this kind might be used for squaring a corner
under a shoulder. Tool _L_ is frequently used on boring mills for
rounding the corners of flywheel rims, in order to give them a more
finished appearance. It has two cutting edges so that either side can be
used as when rounding the inner and outer corners of a rim.

The turning tools of a vertical boring mill are