Comparison of N, NU, NJ, NF, NUP Type Cylindrical Roller Bearings
Introduction
Cylindrical roller bearings have a large load capacity and mainly bear radial loads. Its structure is simple, including cylindrical rolling elements, inner rings, outer rings, and retainers. Single-row cylindrical roller bearings are the most basic type. Its different structures are reflected in the different designs of the ribs. Common basic cylindrical roller bearing types include N NU, NJ NF, and NUP. This article will introduce the characteristics and applications of these types to help you further understand.
The following chart is a simple summary of the comparison of the different rib types for cylindrical roller bearings.
| Type | Inner Ring | Outer Ring | Axial Displacement | Axial Load |
|---|---|---|---|---|
| N | Double Rib | No Rib | Large | None |
| NU | No Rib | Double Rib | Large | None |
| NJ | Double Rib | Single Rib | Limited | Small One-Way |
| NF | Double Rib | Single Rib | Poor | Large One-Way |
| NUP | Single Rib + Loose Ring | Double Rib | Restricted | Two-Way |
If you still need more detailed information, please continue to read the following parts.
N Type Cylindrical Roller Bearings
Description
The outer ring of N cylindrical roller bearings has no ribs, and the inner ring has ribs on both sides. The N type design allows the shaft to move relative to the bearing seat in both axial directions. The inner ring can move axially relative to the outer ring, which is very suitable for applications where thermal expansion occurs. This type is suitable as a free-end bearing. However, it cannot bear any thrust load.
Application
The N Type Cylindrical Roller Bearings are commonly used in electric motors, pumps, and compressors.
NU Type Cylindrical Roller Bearings
Description
The NU cylindrical roller bearing has ribs on both sides of the outer ring and no ribs on the inner ring. The NU type allows displacement of the shaft relative to the bearing seat in both axial directions. This kind of structure is suitable for use as a free-end bearing. It can accommodate expansion and contraction. It can only carry radial loads.
Application
Similar to the N type, the NU type bearing is also often used as a free-end support in situations where the shaft is elongated due to heat or the installation error is large. It is suitable for high-speed occasions, such as high-speed motors and compressors.
NJ Type Cylindrical Roller Bearings
Description
The NJ cylindrical roller bearing has two ribs on the outer ring and one rib on the inner ring. The inner ring of the NJ bearing has a rib on one side and can be separated from the bearing assembly on one side. The design is capable of withstanding limited axial loads in a single direction.
Application
The NJ bearings are widely used in machine tools, turbines and industrial fans where a certain amount of axial load is required.
NF Type Cylindrical Roller Bearings
Description
The NF cylindrical roller bearing has ribs on one side of its outer ring and ribs on both sides of its inner ring. It is designed to withstand a certain amount of unidirectional axial load. This type of structure is suitable for use as a one-way axial positioning bearing.
Application
Due to its high radial load capacity, NF bearings are often used in equipment that bears large loads, such as rolling mills and heavy machinery.
NUP Type Cylindrical Roller Bearings
Description
NUP cylindrical roller bearings have ribs on both sides of the outer ring, a (fixed) single rib on one side of the inner ring, and a detachable flat ring on the other side. They can withstand a certain amount of bidirectional axial load. This type of structural bearing can limit the displacement of the shaft relative to the bearing seat in both axial directions. Therefore, it is suitable for use as a fixed-end bearing.
Application
NUP bearings can bear bidirectional axial loads, so they can be used in situations where bidirectional axial positioning is required. They are often used in high-precision machine tools, precision instruments and other equipment that have high requirements for axial positioning.
Conclusion
In general, single row cylindrical roller bearings are classified into five basic types according to the design of the ribs: N, NU, NJ, NF, and NUP. N and NU types are mainly used to bear radial loads and are used as free-end bearings. NJ and NF types can bear unidirectional axial loads and are used as fixed-end bearings. NUP type can bear bidirectional axial loads. Knowing these differences will help you better choose the right bearing for your equipment.
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FAQs
How to choose the right type of cylindrical roller bearing?
Only bear radial loads and require axial displacement: Select N type or NU type.
Bear radial loads and unidirectional axial loads, require unidirectional axial positioning: Select NJ type or NF type.
Bear radial loads and bidirectional small axial loads, require axial positioning: Select NUP type.
Which bearing type is suitable for high axial loads?
NJ and NUP type cylindrical roller bearings are ideal for applications with higher axial loads due to their additional flanges, which provide better axial guidance.
Are the N, NU, NJ, NF, and NUP bearings interchangeable?
These bearings are not always interchangeable due to the different internal configurations and design features. For example, NU bearings allow for axial displacement, while NJ and NUP bearings offer some axial guidance, so selecting the correct bearing depends on the specific application requirements.
How are N and NU type bearings selected in practical applications? What precautions should be taken?
Usually the choice is based on the expansion direction of the shaft and the bearing seat. If the shaft expands more than the bearing seat, usually choose NU type; otherwise, choose N type. It should be noted that neither of these two types of bearings can withstand axial loads.
Besides single-row cylindrical roller bearings, what other types of cylindrical roller bearings exist? What are their characteristics?
There are also double-row cylindrical roller bearings (NN, NNU) and four-row cylindrical roller bearings. Double-row bearings have higher radial load capacity, while four-row bearings are often used in heavy-load situations such as rolling mills.