. 15.
The lining _L_ is mounted in two cast-iron ring-shaped fixtures _F_.
These fixtures are circular in shape and have flat bases which are
bolted to the table of the machine. On the inside of each fixture, there
are four equally spaced wedges _W_ which fit into grooves as shown in
the end view. These wedges are drawn in against the work by bolts, and
they prevent the lining from rotating when a cut is being taken. This
form of fixture is especially adapted for holding thin bronze linings,
such as are used in pump cylinders, because only a light pressure
against the wedges is required, and thin work can be held without
distorting it. If a very thin lining is being bored, it is well to
loosen the wedges slightly before taking the finishing cut, so that the
work can spring back to its normal shape.

[Illustration: Fig. 15. Cylinder Lining mounted in Fixture for Boring]

[Illustration: Fig. 16. Detrick & Harvey Horizontal Boring Machine of
the Floor Type Boring Engine Bed Casting]

=Horizontal Boring Machine of Floor Type.=--The type of horizontal
boring, drilling and milling machine, shown in Fig. 16, is intended for
boring heavy parts such as the cylinders of large engines or pumps, the
bearings of heavy machine beds and similar work. This machine can also
be used for drilling and milling, although it is intended primarily for
boring, and the other operations are usually secondary. This design is
ordinarily referred to as the "floor type," because the work-table is
low for accommodating large heavy castings. The spindle _S_ which drives
the boring-bar, and the spindle feeding mechanism, are carried by a
saddle. This saddle is free to move vertically on the face of column
_C_ which is mounted on transverse ways extending across the right-hand
end of the main bed. This construction permits the spindle to move
vertically or laterally (by traversing the column) either for adjusting
it to the required position or for milling operations. The spindle also
has a longitudinal movement for boring. There is an outer bearing _B_
for supporting the boring-bar, which also has lateral and vertical
adjustments, so that it can be aligned with the bar.

The work done on a machine of this type is either clamped directly to
the large bed-plate _A_ (which has a number of T-slots for receiving the
heads of the clamping bolts) or, in some cases, a special fixture may be
used or an auxiliary table. Boring machines of this same general
con