Page 76 - 4637

In a cross section of 2-cone bit, cutters, or cones, are
mounted on bearing pins which are an integral part of the bit body.
This provides necessary strength to withstand loads imposed on
bits in present-day drilling. Radial loads are taken by the roller
bearing near the cutter base and by plain bearing near the nose.
The ball bearing retains the cutter on bearing pin and absorbs
all inward thrust loads. The primary capacity for outward thrust is
obtained by providing a plain thrust bearing at the ball race inner
flange face and at the inner end of the bearing pin.
This 5-element bearing design is typical for most types of
3-cone bits in sizes from 4 ¾ in. to 12 ¾ in. A recent trend in
bearing design is to replace roller bearings with a plain or journal
bearing as primary radial load element. In larger bits additional
space available permits use of two or more roller bearings for
increased capacity. Because of space limitations in most types of
bits smaller than 43 ¾ in., a ball bearing in combination with an
outer and inner plain bearing is used.

Figure 6.4 – Steel tooth bits

75