Why Do Previously Purchased Motors Have a Hole in the Shaft End, While New Ones Do Not?

During the motor selection and usage process, many customers notice a subtle design change: motors purchased years ago often have a center hole on the shaft end face, while the same model purchased recently may no longer have this feature. This is not an arbitrary change by our company, but an optimization resulting from the evolution of manufacturing processes.

1. The Original Purpose of the Shaft End Center Hole

This hole, known in the industry as a shaft end center hole, primarily serves the motor manufacturing process:

• Machining Positioning Reference: During precision machining of the motor shaft, such as turning and grinding, the center hole is a crucial reference point for center positioning, ensuring the shaft's coaxiality and dimensional accuracy.
• Rotor Dynamic Balancing: After rotor assembly, the center hole can serve as a positioning point for fixtures during high-speed dynamic balancing tests and corrections, ensuring smooth motor operation.
• Aiding Assembly and Maintenance: In certain scenarios, the center hole can also be used for threaded connections on the shaft end, facilitating the installation or removal of tools during assembly or repair.

2. Design Change Driven by Process Improvement

With advancements in manufacturing technology, motor producers have gradually optimized processing techniques, significantly reducing the necessity of the shaft end center hole:

• Maturity of Centerless Machining Technology: Developments in modern CNC machine tools and fixture technology allow for high-precision machining of motor shafts without relying on traditional center hole positioning. For example, using three-jaw chucks or face drivers can equally ensure machining accuracy.
• Upgraded Balancing Processes: New dynamic balancing equipment and correction methods no longer require the shaft end center hole as the sole positioning reference, simplifying the production流程.
• Cost and Reliability Considerations: Eliminating the center hole removes a machining step, reducing production costs. Simultaneously, it avoids potential issues like stress concentration and rust at the hole's location, enhancing the overall strength and reliability of the motor shaft.

3. Impact on User Application

For the vast majority of end users, the removal of the center hole on the motor shaft end does not affect normal usage. Core performance parameters such as the motor's output torque, speed, and mounting dimensions remain unchanged.

Updated on: 28/02/2026