which is centered with the bar and
cutter in order to properly locate the casting. There is a bearing at
each end of the casing, and two larger ones in the center. These are
bored by flat cutters similar to the style illustrated at _A_ in Fig. 3.
The cutter for the inner bearings is shown at _c_.

[Illustration: Fig. 13. Facing and Turning Flange of Differential Gear
Casing]

After the bearings are bored, the circular table is turned 90 degrees
and the work is moved closer to the spindle (as shown in Fig. 13) for
facing flange _F_ at right angles to the bearings. Circular flanges of
this kind are faced in a horizontal boring machine by a special
facing-arm or head _H_. For this particular job this head is clamped
directly to the spindle sleeve, but it can also be clamped to the
spindle if necessary. The turning tool is held in a slotted toolpost,
and it is fed radially for turning the side or face of the flange, by
the well-known star feed at _S_. When this feed is in operation the bent
finger _E_ is turned downward so that it strikes one of the star wheel
arms for each revolution; this turns the wheel slightly, and the
movement is transmitted to the tool-block by a feed-screw. The
illustration shows the tool set for turning the outside or periphery of
the flange. This is done by setting the tool to the proper radius and
then feeding the work horizontally by shifting the work-table along the
bed. By referring to Fig. 12 it will be seen that the facing head does
not need to be removed for boring, as it is attached to the spindle
driving quill and does not interfere with the longitudinal adjustment of
the spindle. This facing head is also used frequently for truing the
flanges of cylinders which are to be bored, and for similar work.

[Illustration: Fig. 14. Example of Work requiring Boring and Milling]

Fig. 14 shows another example of work which requires boring and milling.
This casting is mounted on a fixture which is bolted to the main table.
In this case the circular table is not necessary, because the work can
be finished without swiveling it around. After the boring is completed
the edge _E_ is trued by the large-face milling cutter _M_ bolted to the
spindle sleeve. The irregular outline of the edge is followed by moving
the table crosswise and the spindle vertically, as required.

=Fixture for Cylinder Lining or Bushing.=--A method of holding a
cylinder lining or bushing while it is being bored is shown in Fig