Understanding Antifriction Bearings

Antifriction bearings are a type of rolling-element bearing designed to reduce friction between moving parts. They achieve this by using rolling elements, such as balls or rollers, placed between two rings (races). This rolling motion significantly lowers the friction compared to sliding motion found in plain bearings.

Analyzing Bearing Types

Let's examine the provided options to determine which one fits the definition of an antifriction bearing:

1. Journal Bearing

A journal bearing, also known as a plain bearing or sleeve bearing, typically operates on the principle of sliding friction. Lubricant film separates the surfaces, but the primary mode of operation involves sliding contact. Therefore, it's generally not classified as an antifriction bearing in the context of rolling elements.

2. Pedestal Bearing

A pedestal bearing refers to the housing or mounting structure that supports a bearing assembly. The bearing itself could be either a plain bearing or an antifriction bearing. The term itself doesn't specify the type of friction mechanism.

3. Collar Bearing

A collar bearing is a type of thrust bearing designed to support axial loads. While some collar bearings can incorporate rolling elements, many are designed as plain bearings where a collar on a rotating shaft slides against a stationary surface, often relying on hydrodynamic lubrication. It's not exclusively an antifriction bearing type.

4. Needle Bearing

A needle bearing is a specific type of roller bearing. It uses long, thin cylindrical rollers, called needles. These needles roll between the inner and outer races, providing a low-friction interface and high load-carrying capacity in a small radial space. As it utilizes rolling elements (needles), it is a classic example of an antifriction bearing.

Conclusion on Antifriction Bearings

Based on the analysis, the Needle bearing is the correct classification as an antifriction bearing because it utilizes rolling elements (needles) to minimize friction.