Needle Roller Bearing without Inner Ring

Space-saving design
Without an inner ring, the bearing can be installed in a smaller radial space.

 

Direct shaft contact
The needle rollers run on the shaft surface, so the shaft needs to have suitable hardness and surface quality.

 

Good radial load support
The needle rollers have a relatively large contact area with the raceway and are mainly used for radial loads.

 

Simple arrangement
Removing the inner ring leaves more room for the shaft and surrounding components.

Part Number: HK3020

Type: Drawn cup needle roller bearing, without inner ring

ID: 30 mm

OD: 37 mm

Width: 20 mm

This type of needle roller bearing is suitable for compact rotating mechanisms in which radial installation space is restricted. Typical applications include small gear drives, power tools, textile equipment, pneumatic tools and selected household appliance motors. The actual suitability depends on shaft condition, housing dimensions, load, speed and lubrication requirements.

The ZWZ NK series is a needle roller bearing design without a separate inner ring. It is intended for applications where the housing provides the required support and the shaft can be prepared to serve as the raceway.

Compared with a bearing arrangement that uses an inner ring, this configuration can reduce the radial envelope of the assembly and leave more flexibility for shaft sizing. It is often selected for compact transmission systems and mechanical components where installation space is an important design consideration.

For reliable operation, the shaft surface should meet the required hardness, surface finish and dimensional tolerances. These conditions directly affect the running contact between the shaft and the needle rollers.

No separate inner ring: The shaft functions as the raceway, helping reduce the overall radial size of the bearing arrangement.

 

Compact bearing section: The thin outer ring and needle roller assembly are suitable for mechanisms where available space is limited.

 

Radial load capability: The needle rollers provide line contact with the raceway, allowing the bearing to support radial loads effectively within its operating limits.

 

Flexible shaft arrangement: Removing the inner ring can leave more usable space for the shaft and surrounding components.

 

Common bearing sizes: Standardized dimensions make model selection and replacement easier when the shaft, housing and operating conditions are compatible.

Needle roller bearings without inner rings are used in compact mechanical assemblies such as pumps, compressors, textile machinery, small gearboxes and automation equipment. They are particularly useful when the housing has limited radial space and the shaft can be manufactured or finished to work directly as the bearing raceway.

When selecting a bearing for a specific application, shaft hardness, raceway surface quality, radial clearance, load, speed and lubrication should be considered together rather than selecting the bearing only by nominal dimensions.

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