does needle roller bearing always has inner race?

Not all needle roller bearings are equipped with an inner ring.

There are two common types:

1. Needle Roller Bearings with an Inner Ring
These bearings come with a precision inner ring, allowing them to be mounted directly onto the shaft. They are easy to install and place lower requirements on the shaft's hardness and surface finish.

2. Needle Roller Bearings without an Inner Ring (also known as drawn cup needle roller bearings or full complement needle roller bearings, depending on the design)
These bearings do not include an inner ring. Instead, the needle rollers run directly on the shaft surface or the housing bore. This design minimizes radial space and provides a more compact structure. However, it requires the shaft raceway to have sufficient hardness and high machining accuracy, typically achieved through heat treatment and precision grinding.

Therefore, whether a needle roller bearing includes an inner ring depends on the specific bearing design and the application's requirements.

If you'd like, I can also help you choose the most suitable type based on your application.