Journal Bearing

Table of Contents

A journal bearing is a device that helps reduce the amount of friction between two moving parts. You will typically find this type of bearing in machines that generate a great deal of heat, such as turbines and jet engines. The journal bearing relies on a layer of oil to help reduce friction. Journal bearing composition can be a variety of materials, including stainless steel and bronze. To keep the oil in good condition, it is important to regularly clean and lubricate the journal bearing. By taking care of your journal bearings, you can help ensure that your machine runs smoothly for years to come.

What is a Journal Bearing?

One of the most straightforward and widely used hydrodynamic bearing types is the journal bearing. Their primary function is to hold up a rotating shaft. A journal bearing is a type of bearing that permits a shaft to freely rotate inside a supporting shell or sleeve. They support crankshafts and camshafts in a variety of engine and powertrain subsystems. Journal bearings experience lower loads than ball and rolling bearings. So, journal bearings normally function under hydrodynamic lubrication.

Why are Journal Bearings Critical?

Journal bearings are crucial because they extend the lifespan of engineering systems while being inexpensive. They are one of the most common types of bearings. Also, they are useful in numerous technical industries due to their simple design and manufacturing requirements.

The Different Types of Journal Bearings


Objects with integral plain bearings have a hole in them to serve as bearing surfaces. Bearings made of pillow blocks are the most common type of integral journal bearing. Typically, pillow block bearings have a cast iron housing and chromium steel alloy bearing surfaces. To maintain effective lubrication throughout their lifetime, they usually have grease nipples on the housing.


Bushings are mechanical components that provide a bearing surface in housings. The housing and shaft size determine the bushing’s internal and external diameters. Sleeves can be either plain or flanged, which is the most common type of bushing.


As the name implies, a two-piece journal bearing is a bearing with two parts or halves. These two shells are perfect for applications with a big diameter, such as a crankshaft. It is typical to employ a dowel to stop the bearing from moving while it is in use. The two halves of this type of journal bearing are made somewhat larger than their housing, just like roller and ball bearings. The shells are compressed during installation, creating a radial force that stops the bearing from spinning.

Typical Journal Bearing Construction

White metal is a material that is frequently used in journal bearings. Babbit metal, a kind of white metal, is utilized as the bearing surface. Babbitt metal has hard crystals embedded within its soft matrix. As the softer portion of the metal ages, a lubricating coating forms between the journal and the babbitt metal’s tougher particles. Rotation is aided by the hard particles’ ability to create a route and wear down the surrounding surface. Tin is a common component of babbitt metal; when there is friction, it melts and serves as a lubricant.

A backing material, which is a harder substance, is another component of journal bearings. Bronze or copper alloys are frequently used as the material for two-piece journal bearings. CC493K, SAE 660, and LG4 (BS 1400) are standard backing bronze materials. Despite having slightly varied elemental combinations, all of these bronzes have the same function. The atmosphere can somewhat alter the composition of bronze. For instance, CC493K has a greater zinc level of 3.0% to 5.0%. Higher zinc concentration offers better seawater corrosion resistance, which makes it desirable for maritime applications.

Lubrication Management Vital to Bearing Life

Bearing life is a major factor in the overall efficiency of a machine. That’s because bearing failures are one of the most common, and costly, problems businesses face. Not only do you need to understand your bearings, but you need to care for them. By correctly implementing a lubrication management plan, however, these failures can be avoided. Lubrication management is critical to preserving bearing life and ensuring that your machine operates at its best.

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