Journal bearings rely on fluid films(usually oil) to support rotating shafts. Ball bearings provide the same support of shafts through mechanical means. Both bearings are used to counter radial and axial loads.

Journal Bearings

• The portion of the shaft supported by the bearing is called the journal and is usually hardened for wear-resistance. Bearing pad material is usually a softer material such as tin- and lead-based babbitt, bronze, copper-lead, sintered powdered metal, carbon, PTFE, etc.
• As the shaft rotates in the bearing clearance it tends to want to climb up the bearing wall, creating a region of high pressure in the oil film which supports the shaft journal. As the load on the shaft varies, so too does this region of high-pressure, making journal bearings quite tolerant of overloads and shock loads.
• Journal bearings are affected by the misalignment between bearing and shaft as its presence tends to hamper the formation of the fluid film.

Ball Bearings

• A typical ball or roller bearing consists of inner and outer raceways, a number of spherical, cylindrical, tapered, or semi-cylindrical elements separated by a carrier, and, often, shields and/or seals designed to keep dirt out and grease in.
• Shaft and bearing alignment play a critical role in bearing life. For higher misalignment capacity, self-aligning bearings are used.

Journal bearings require less radial space than ball bearings but need more length axially.And Journal ballings are more capable of managing shock and overload compared with ball bearings. They are also less prone to fatigue.

Ball bearings, because of their low starting friction, are the preferred choice for intermittent operations and cold environments. They are much more adapted to handling misalignment between shaft and bearing with self-aligning designs available to increase this capacity.

Worn journal bearings often require rebabbitting and renewal of the journal surface. Rolling-element bearings can usually be replaced as units.