Steel Tooth Cutting Structures
There are three basic design features incorporated in steel tooth cutting
structures, teeth spacing, tooth hardfacing, and tooth angle (Figure 3-4).
Using variations of these parameters, bits are separated into formation
types.
Soft Formation Cutting Structures
Teeth on this type of bit are few in number, widely spaced,
and placed in a few broad rows. They tend to be slender, with
small tooth angles (39° to 42°). They are dressed with hard
metal.
Medium Formation Cutting Structures
Teeth on medium formation bits are fairly numerous, with
moderate spacing and depth. The teeth are strong, and are a
compromise between hard and soft bits, with tooth angles of
43° to 46°. The inner rows as well as the gauge rows are
hardfaced.
Hard Formation Cutting Structures
There are many teeth on this type of bit. They are closely
spaced and are short and blunt. There are many narrow rows
with tooth angles of 46o to 50o. The inner rows have no
hardfacing, while the gauge row is hardfaced.
