What is a ball screw?

According to THK definition:

The Ball Screw is a high-efficiency method of converting rotary motion to linear motion by using a recirculating ball mechanism between the screw shaft and the nut. Compared with a conventional sliding screw, the ball screw requires driving torque of one-third or less, making it ideal for saving drive motor power.


It is a mechanical component widely used in machinery and automation systems to convert rotational motion into linear motion. It’s a type of screw mechanism that employs a set of ball bearings within a threaded shaft and a nut. This arrangement allows for efficient and smooth motion transfer, making it ideal for machines that require precise positioning and low friction.

Basic components

It is very helpful to know the components when it comes to a ball screw. If you have a knowledge about each component, you will get a better understanding of the mechanism’s function.

  1. Threaded Shaft: The threaded shaft is the primary component of the ball screw. It’s a long rod with helical threads cut along its length. The threads create a track for the ball bearings to move along.
  2. Nut: The nut is a cylindrical component with matching threads that engage with the threads on the shaft. The nut contains the recirculating system for the ball bearings.
  3. Ball Bearings: The ball bearings are small, spherical components that roll between the threads of the shaft and the grooves in the nut. These ball bearings facilitate smooth movement along the threads.

How it works

A ball screw operates by converting rotational motion into linear motion with the help of ball bearings. The threaded shaft has helical grooves (threads) cut along its length. Inside the nut, there are ball bearings that fit into these threads. As the shaft rotates, the ball bearings move along the threads, pushing the nut linearly along the shaft. This transforms the rotational energy into smooth and precise linear movement, making ball screws essential for applications requiring accurate positioning and efficient motion transfer.

Advantages of ball screws

  1. High Efficiency: Rolling ball bearings reduce friction, ensuring efficient energy transfer and minimal power loss.
  2. Precision Positioning: Ball screws provide accurate and repeatable positioning, critical in tasks like CNC machining and robotics.
  3. Low Friction: Rolling contact lowers friction, extending component lifespan and reducing energy consumption.
  4. Minimal Backlash: Tight manufacturing tolerances lead to minimal play between components, ensuring precise motion.
  5. Quiet Operation: The smooth rolling of ball bearings produces less noise compared to other motion mechanisms.
  6. High Load Capacity: Ball screws handle significant axial loads, making them suitable for heavy-duty applications.
  7. Speed: Their design permits high-speed motion with minimal wear, maintaining accuracy.
  8. Longevity: Reduced wear and lower friction contribute to extended service life.
  9. Accuracy in Multi-Axis Machining: Ideal for applications requiring multi-axis and intricate movements.
  10. Reduced Maintenance: Low wear and efficient lubrication systems lead to less frequent maintenance needs.

The advantages it brings – from precision positioning and low friction to high load capacity – have propelled it into the heart of modern machinery, from CNC machining to robotics. As industries continue to push boundaries, the ball screw remains a steadfast companion, enabling the intricacies of our technological progress with each graceful turn.

At BIYOUN, we pick the top-notch ball screw brands like PMI and THK. These trustworthy parts help our machines work really accurately and stay strong for a long time.