Journal Angle
One of the basic design fundamentals of rolling cutter rock bits is the journal angle. Though this angle may vary from one rock bit type to the next, in each bit the three journal angles are all identical.
The journal angle (Figure 3-1) is the angle at which the journal is mounted, relative to a horizontal plane. This mounting moves the cutting elements (cones) outside the support members. The journal angle also controls the cutter profile or pattern it drills, and it affects the amount of cutter action on
the bottom of the hole.
Journal angles are different for each “type” of formation:
Soft Formations
Journal angle (33o) - this allows a cutter profile which accentuates cutter action and permits greater tooth depth.
Medium Formations
Journal angle (34o to 36o), to decrease cutter action.
Hard Formations
Uses a large journal angle (39o), to minimize cutter action.
One of the basic design fundamentals of rolling cutter rock bits is the journal angle. Though this angle may vary from one rock bit type to the next, in each bit the three journal angles are all identical.
The journal angle (Figure 3-1) is the angle at which the journal is mounted, relative to a horizontal plane. This mounting moves the cutting elements (cones) outside the support members. The journal angle also controls the cutter profile or pattern it drills, and it affects the amount of cutter action on
the bottom of the hole.
Journal angles are different for each “type” of formation:
Soft Formations
Journal angle (33o) - this allows a cutter profile which accentuates cutter action and permits greater tooth depth.
Medium Formations
Journal angle (34o to 36o), to decrease cutter action.
Hard Formations
Uses a large journal angle (39o), to minimize cutter action.
