Lead Screw vs Ball Screw

The lead screw vs. ball screw debate has been on for a long time. People often get confused about which to use and when to use it. Some people say they can be used interchangeably, but that is not true. Each of them has its specific application methods. 

This article will help you identify and understand the differences between the two screws.

What Is A Lead Screw?

Lead Screw

A lead screw or power screw, or translation screw, is used in machines as a linkage and to change turning motions to linear motion. Unlike any other screw, lead screws have a threaded nut and threaded bars of metal that help create sliding friction when it is being turned. 

What Are The Types Of Lead Screws?

Lead screws are generally classified by the way their threaded bars are woven. There are three types of thread patterns, acme / trapezoidal thread, square thread, and buttress thread. Each threaded bar style provides different friction levels, some more than others.

Acme / Trapezoidal Thread

Developed in 1894, the acme or trapezoid thread form is the most commonly used and preferred lead screw. As its name implies, the threaded bars are styled in a trapezoid shape.

It is used on various equipment such as conveyors, valve stems, hose connectors, etc. It is also used for testing machines, movements in camera lenses, and machine tools. 

Square Thread

Square thread forms were made way before acme / trapezoidal threads. They are commonly used in machines for heavy loading and lifting, screw jacks, and press machines. Square thread forms are also known as the most efficient thread forms.

Buttress Thread

The buttress thread has an asymmetric thread form; the driving face is slanted and perpendicular to the axis of the screw, while the back face is angled. Its thread style allows it to be much more efficient in lifting heavy loads than acme threads and square threads.

What Are The Pros And Cons Of A Lead Screw?

The pros of having lead screws are:

  • It is suitable for heavy lifting.
  • Lead screws are simple and easy to manufacture.
  • They do not have lots of parts.
  • Lead screws are cost less and are really easy to maintain.

These are the cons of lead screws:

The major disadvantage of lead screws is the high friction caused by the way their threads are created. It spoils/wears out the screw faster.

What is a Ball Screw?

Ball Screw

A ball screw is a precision screw, similar to a lead screw, in that both are used in machines to turn rotary movements into linear ones. The only difference is ball screws do so with little friction. The ball bearings running in the helical channel transmit the load. 

Due to the complex method through which ball screws are created, they are more complicated to use but have a better performance than other screws. This, in turn, makes it more costly than others.

Types Of Ball Screws

Ball screws are also classified based on their thread pattern and shaft. There are two main types, rolled ball screw and ground ball screw. 

Rolled Ball Screw

Rolled ball screws are used for applications where the load needs to be transported from one side to the other. The threads are created by weaving uncut bars through rotating tool dies at once. A rolling process is used to automate the screws to increase the production rate of the screw.

Ground Ball Screw

Ground ball screws are manufactured differently. They are created by allowing a tough, abrasive cutter along the body of the blank and with more precision and attention to detail. Ground ball screws are primarily used in applications that require more repeatability. 

What Are The Pros And Cons Of Ball Screws?

Pros:

  • Ball screws are more efficient than other screws.
  • They produce much lesser friction. This will help reduce wear and tear.
  • There are higher accuracy grades available.
  • They can be adjusted to decrease or increase preload.

Cons:

  • Ball screws are noisy.
  • They require braking mechanisms.
  • For design purposes, they need to be lubricated regularly.
  • They are more expensive than lead screws.

Which One Should You Use?

It all boils down to what you want, where, and what you need to use it for. While both screws are suitable for heavy lifting, the ball screw is much better for the job. It is costlier, but you get value for your money.