For the teeth of roller cone bits, the basic requirements are high rock breaking efficiency and long life. In order to meet this requirement, first, the geometric shape of the teeth must be reasonable; second, the material of the teeth must be wear-resistant and have sufficient strength.
According to the type of teeth, roller cone bits can be divided into milling teeth (also called steel teeth) and cemented carbide teeth (referred to as inserts).
1. Milling tooth profile
The teeth of the milling cone bit are integrated with the cone shell. It is formed by milling the cone blank. In order to improve the wear resistance of the teeth, cemented carbide powder is applied on the tooth surface.
The tooth profile of milling teeth is mainly wedge-shaped teeth. The outer gauge gears can be made into P, T, and L shapes.
2. Insert tooth profile
a. Wedge-shaped teeth: suitable for crushing soft formations with high plasticity and medium-hard formations, with tooth tip angles ranging from 65 to 90 degrees, small tooth tip angles are suitable for soft formations, and large tooth tip angles are suitable for harder formations.
b. Scoop chisel: There is also a kind of wedge tooth with asymmetrical sides, one side of which is concave, called scoop chisel, suitable for drilling soft formations.
c. Conical tooth: There are two kinds of single cone and double cone. The rock is crushed by crushing method. The medium cone tooth of 60°-70° is used to drill medium and hard formations, such as limestone and dolomite. 90° cone and 120° double cone teeth are suitable for hard formations with high abrasiveness, such as hard sandstone and quartzite.
d. Triangular tooth: a plane is cut every 120° on the cone surface of the double cone tooth, which is suitable for the interlaced layer of hard and brittle stratum and soft and plastic stratum.