• A journal bearing, in its simplest form is a
cylindrical bushing made of a suitable material
and containing properly machined inside and
outside diameters. The journal is usually the
part of a shaft or pins that rotates inside the
3. Simple journal or solid bearing
It is simply a block of cast iron with a hole for the
shaft providing running fit. An oil hole is drilled at
the top for lubrication.
The main disadvantage of this type of bearing are
There is no provision for wear and adjustment on account of
The shaft must be passed into the bearing axially, i.e. endwise.
Limited load on shaft and speed of shaft is low.
6. Bearing Diagram
Journal bearing - used to support the load on a rotating shaft.
Oil inlet – used to insert the oil/lubrication
As lubricating oil is fed into the bearing and is dragged by the shaft into
the converging gap, the fluid pressure increases and a hydrodynamic lift is
Axial oil groove have some space to prevent from oil loss.
• It handle high load and velocities because metal to metal
contact is minimal due to the oil film.
• The journal bearing is remarkably durable and long lasting
• The damping effect of the oil film, journal bearing help
make engines quiet and smooth running.
• They require large supply of lubricating oil.
• Suitable only for relative low temperature and speed.
• Starting resistance is much greater than running resistance
due to slow build up of lubricant film around the bearing
• Journal bearing are widely use in gasoline
and diesel fueled piston engine in motor
vehicle and allowed parts to move together
smoothly. Journal bearing are considered to
be sliding bearing as opposed to rolling
bearings such as ball bearings.