What is the difference between needle roller bearings and ball bearings?

Needle roller bearings and ball bearings are two common types of rolling bearings. They have significant differences in structure, performance, application situations, etc.

1. Structural differences
Needle roller bearings: The rolling elements of needle roller bearings are thin and long cylindrical rollers, which are called needle rollers. Its characteristic is that the roller diameter is small (usually diameter D≤5mm, and L/D≥2.5, L is the length of the roller), making the bearing very compact in radial structure. Needle roller bearings can be designed without an inner ring and fit directly with the shaft, further saving space.
Ball bearings: The rolling elements of ball bearings are spherical alloy steel balls. These steel balls are installed between the inner and outer steel rings and roll to reduce friction during power transmission and improve mechanical power transmission efficiency. Ball bearings contain four basic elements: balls, inner ring, outer ring and cage.

2. Performance differences
Load-carrying capacity: Under the same size, ball bearings usually have a higher load-carrying capacity because of the larger number of balls and the load each ball bears is relatively small. Although the number of needle rollers in needle roller bearings is small, each needle roller can withstand greater pressure on a smaller contact area due to its smaller diameter. Therefore, in some specific situations, its load-bearing capacity is also considerable. Especially when the radial installation dimensions are limited.
Speed ​​of use: Ball bearings usually have a higher speed limit due to their spherical ball design, which has a smaller contact area and better lubrication conditions. In contrast, needle roller bearings may generate large centrifugal force and inertial force when running at high speed due to the long length of the needle roller, thus limiting the rotational speed during use.
Space utilization: Due to the design of the needle roller, needle roller bearings can be made smaller and save space, which is very suitable for certain occasions with limited space. Although ball bearings are also compact, in some extreme situations where space saving is required, needle roller bearings may have more advantages.
Rigidity and stability: Due to the design of the needle roller, needle roller bearings can provide higher rigidity and stability, especially in situations where large load-bearing capacity and high-precision equipment are required. Although ball bearings also have good stability and accuracy, they may not be as good as needle roller bearings in situations with extremely high rigidity requirements.

3. Application occasions
Needle roller bearings: Needle roller bearings are particularly suitable for support structures with limited radial installation dimensions, such as automobile transmissions, differentials, engines and other components. At the same time, due to its high rigidity and load-bearing capacity, it is also often used in the transmission system of heavy machinery and equipment.
Ball bearings: Ball bearings are widely used in various mechanical equipment, especially in low-load, high-speed rotation situations. For example, ball bearings are often used as bearings in motors, fans, water pumps and other equipment. Ball bearings are also commonly used in transmission systems of precision instruments and equipment to ensure high precision and long life.