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engage the lock collar and may be used to lock the table against
rotation in either direction.
The assembly is factory-aligned, or equipped with self-
aligning bearings, to prevent required adjustment of the contact
with the main gear in the field. The teeth of the pinion gear also
are hardened to resist wear.
Most of the moving parts in the rotary table are flood
lubricated, the remainder lubricated through conveniently located
grease fittings. The main base acts as a sump which holds the oil in
which the ring gear and main bearing run. Although the pinion is
flood lubricated, it is not always lubricated from the same sump as
the ring gear. Some manufacturers provide a separate reservoir to
carry the lubricating oil for pinion gear and inner pinion bearing.
The out pinion bearing and hold-down bearing are usually grease
lubricated. The particular advantage in a machine completely flood
lubricated is that greasing up every tour can be eliminated.
Lubrication oil need be added to the rotary table infrequently.
The main base, in addition to serving, as an oil sump,
provides support for the table casting, through the main bearing,
and for the pinion shaft assembly. It is frequently an alloy steel
casting, but may be welded from preformed steel plate. The top of
the base is provided with a non-skid surface. A tongue-and-groove
labyrinth seal between table and the base make the lubrication
system slush proof.
The size of the rotary table is taken from the diameter of the
opening in the table through which the tool passes. The practical
limit to size of opening is governed by both ability of moving parts
to withstand the increased loads imposed upon them by virtue of
their larger size, and the logical upper limit of hole diameter. The
largest tables today have an opening of 49 in. The 27 in table,
however, suffices for most drilling purposes. With new drilling
techniques, rotary speeds greater than 300 rpm sometimes are
necessary.

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