Mood 3 Products

What's a bearing

The bearing in its current form was developed towards the end of the 19th century. It was initially made by hand.

Nowadays, bearings are one of the most commonly used machine parts because their rolling motion make almost all movements easier and they help reduce friction.

Bearings have two key functions:

  • They transfer motion, i.e. they support and guide components which turn relative to one another
  • They transmit forces

Rolling bearings and sleeve bearings
In a sleeve or plain bearing, the axle and the bearing move in opposite directions on a sliding surface. By contrast, the two components of a rolling bearing that move towards one another – the inner and outer rings – are separated by rolling elements. This design generates significantly less friction than a sleeve bearing.

Radial bearings and axial bearings
Bearings can transmit loads in a radial direction or an axial direction (thrust) and in many cases there is a combination of both radial and axial loads to transmit.

Both designs are available as ball bearings or roller bearings. The choice of bearing design depends upon the application in question.
Technical Insight - Choosing the Right Bearing and Arrangement

Radial Bearing

Axial Bearing


Bearings usually consist of the following components:

  • Two rings or discs with raceways
  • Rolling elements in the form of rollers or balls
  • A cage which keeps the rolling elements apart and guides them

Inner Ring / Outer Ring

The inner and outer ring are usually made from a special high-purity, chrome alloy steel. This material has the necessary hardness and purity – both important factors for a high load rating and a long service life.
Technical Insight - Bearing Life

The raceways are hardened, ground and honed.

Special materials such as ceramic and plastics are also used. Although plastics cannot withstand extremely high temperatures, they are considerably lighter than steel. This makes them invaluable in sectors such as the automotive industry, where every gram matters.
Technical Insight - Materials for Bearings

Inner Ring

Outer Ring

Rolling elements

Rolling elements are either balls, rollers, cones, spheres or needles. They are usually made from a special high-purity, chrome alloy steel. Special materials such as ceramic and plastics are also used.

The rolling elements roll on the specially formed raceways of the rings or discs and are kept apart and guided by the cage.


The cage is responsible for keeping the rolling elements apart and guiding them. The materials used include steel, brass and plastic. Solid metal cages can be produced using machining techniques, while pressed cages are made from sheet metal. Similarly, plastic cages can be machined from solid plastic or injection moulded.

Our Technical Insights provide a detailed introduction into our Rolling Bearing technology and highlight the performance, benefits & features of NSK’s products.
They refer to the different chapters of our main catalogue "Rolling Bearings".