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10 ROTARY DRIVE MECHANISMS

In the 1800s various primitive type rotary machines were
used to drill both water and oil wells. Birth date of the modern
rotary table, however, is generally taken as 1901 at Spindletop,
Texas. Although the rotary table has been modified and improved
since its conception, it is still essentially the same piece of
machinery. As in early models, the modern rotary table consists of
a ring gear which carries a bushing to drive the drill pipe and the
pinion to drive the ring gear.
The present-day ring gear is spiral beveled, as compared to
the earlier straight bevel gear. The overlapping action of the teeth
tends to eliminate shock and provides a smoother running
machine. The gear machine from alloy steel and the teeth cut
before heat treating. The teeth are then flame-hardened to provide
maximum wear resistance.
The gear table (Fig.10.1) is an alloy steel casting on which
the ring gear and upper race of the main bearing are shrunk. The
table skirt is provided with studs, which secure a ring to lock
positively the hold-down thrust bearing. In addition to carrying up
thrust, the hold-down bearing, together with the main bearing,
provides accurate table alignment.

Figure 10.1 - Rotary table

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