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Ball Screw – Concepts, Invention, and Working Principle

Ball Screw – Concepts, Invention, and Working Principle

Are you looking for mechanical components for converting rotary motion into linear motion with high efficiency without compromising precision? Then look no further than ball screws.

Large-scale industries such as automobile, aerospace, and medical make use of the ball screws as they play a crucial role in precision instruments and machinery tools.

The article focuses on varied aspects of ball screws such as the basic understanding, working principle and mechanism of the ball screws.

What is a Ball Screw? Understanding the Concept and Function

To understand the ball screw we need to first know the components of the ball screw which include screw, nut, steel balls, reverser, pre-compression piece and dustproof device. 

The major function of the ball screw is to convert the rotatory motion to linear motion, which is done by transforming sliding motion to rolling motion. 

Invention of Ball Screw

In 1898, a groundbreaking idea emerged: it involved the use of steel balls positioned between the nut and screw to change the nature of contact from sliding to rolling. This transformation allowed for the rotational movement of the steel balls within the nut to be translated into linear motion. As a result, this innovation significantly enhanced torque conversion efficiency while minimizing positioning issues and damage compared to traditional screws.

The credit for inventing the ball screw goes to Rudolph G. Boehm from Texas, who obtained a US patent for this invention in 1929. In its active role, the nut is converted into linear motion in sync with the screw’s rotational angle, guided by precise specifications. The passive workpiece can be connected to the nut through a nut holder.

Working Principle of Ball Screw

  • Components: A ball screw assembly comprises a screw and a nut, both featuring complementary spiral grooves.
  • Ball Movement: The assembly relies on balls that roll within these grooves, establishing the primary point of contact between the nut and the screw.
  • Ball Return System: When the screw or nut rotates, a deflector directs the balls to a ball return system inside the nut. The balls continuously circulate through this system, exiting to engage the threaded raceway of the ball screw and nut in a closed loop.
  • Critical Role of Ball Nut: The ball nut’s design is pivotal in determining the load-bearing capacity and lifespan of the ball screw assembly. The ratio of threads in the ball nut circuit to those on the ball screw influence, which determines how much sooner the ball nut will reach fatigue failure (wear out) than the ball screw will.
  • Ball Return Methods: Two common ball return methods are employed in ball nuts: outer circulation, where balls return via an extended pipe, and inner circulation, where balls move along the interior wall of the nut.
  • Critical Speed: In cases of high-speed rotation, especially with long ball screws, the slenderness ratio reaching the natural harmonic of the shaft size can induce vibrations known as critical speed. Exceeding 80% of the critical speed is discouraged for safety and to preserve the ball screw’s lifespan.

Are you into manufacturing ball screws for various industrial sectors? If yes then the upcoming IPTEX GRINDEX 2024 expo is the most apt place to showcase your unique product and connect with the industrial leaders. 

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