Journals and Their Types

The parts of a shaft that remain inside the bearing are called journals. Journals are named according to the type of load they carry. Journals that carry load perpendicular to the axis are called radial (support) journals, and journals that carry load parallel to the axis are called thrust journals.

Since journals rotate inside the bearing during operation, they wear. For this reason, journal sections are either hardened or fitted with a bushing to operate against. When bushings wear, new ones are fitted in their place. Rotating journal sections must always be lubricated. When left without lubrication, they wear and seize the bearing.

Types of Journals

End journal: Located at the end of the shaft. Made smaller than the shaft diameter. Two different forms of end journals.

Intermediate journal: Located in the middle sections of shafts. Cross-section and view of an intermediate journal (above)

Spherical journal: Sphere-shaped at the ends of shafts. Used for transmitting angular motion. (above)

Conical journal: The shaft ends are conical in shape. Used in situations where the forces are required to be transmitted perpendicular to the bearing axis (such as in a vehicle’s wheel axles).

Collared journal: Made in a collared shape to carry loads under the effect of very large axial forces. Forces are distributed evenly across the side surfaces of the collars.

Calculating the Load a Journal Can Carry

The journal’s surface loading the bearing = S = d . L
If the pressure on the bearing’s (S) surface = P, then
The applied load = F = P .S, so F = P.d.L

F = The load the journal can carry = kg
P = The bearing’s internal pressure = kg/cm2
d = Bearing and journal diameter = cm
L= Bearing length—cm

Radial Journal

Radial journals are the sections of a shaft that seat in the bearing and carry only radial (perpendicular) loads.

Thrust Journal

Thrust journals are designed to resist forces acting on the shaft in the axial (lengthwise) direction.

Importance of Surface Quality

The smoothness of journal surfaces directly affects the friction and wear between the journal and the bearing.

Related Questions

A journal rotates continuously inside the bearing, and when left without lubrication, the metal surfaces rub directly against each other. This friction rapidly wears down both the journal and the bearing, causing both to fail.

The conical shape allows the applied force to be transmitted perpendicular to the bearing axis. Since both rotational and lateral forces occur in wheel axles, this angled shape handles the forces more appropriately.