When selecting a ball screw assembly, it can be difficult to navigate all the terminology involved. To help you better understand and choose ball screw assemblies, here are some common ball screw terms to know.

Axial Load

A load in which force is distributed parallel to the screw’s axis of rotation. This is the recommended method of loading a ball screw assembly.

Backlash

The lost motion between the nut and the screw. This refers to how much the nut can move without moving along the shaft of the screw.

Circuit

The closed path of recirculating balls within the nut of the ball screw.

Compression Load

A type of load that tends to compress or buckle the screw shaft.

Critical Speed

The angular velocity at which the screw approaches its natural frequency, causing the screw to resonate.

Dynamic Load

The maximum load under which the ball screw can operate for its designated length of travel.

Efficiency

Efficiency is determined by how well a ball screw converts torque (rotational motion) to linear motion. Most ball screws have at least 90 percent efficiency.

Lead

The linear distance traveled in one rotation of the screw.

Lead Error

Also known as accuracy; the difference between the actual and theoretical distance traveled along a ball screw’s shaft.

Life

The total number of rotations or distance a ball screw can travel while bearing a suggested load before significant wear begins.

Lubrication

The greasing or oiling required to reduce friction between the moving parts of the ball screw assembly.

Multiple Start Screw

A screw that has more than one thread and multiple starts.

Pitch

The distance between one screw thread and the corresponding part on the next. Equal to lead on single start screws, but not on multiple start screws.

Pitch Diameter

The diameter a cylinder would have to be to pass through the centers of the ball bearings.

Preloading

A way to eliminate backlash in ball screw assemblies. This is achieved by adding a load between the screw’s nut and shaft, which increases stiffness.

Root Diameter

The minimum diameter of the screw measured at the root (or bottom) of the screw’s threads.

Static Load

The greatest non-operating load capacity at which damage to the assembly’s ball track won’t occur.

Side Load

Also known as radial load. This is a load applied perpendicular to the screw’s axis. This type of load will decrease the life of the ball screw assembly and isn’t normally recommended.

Stiffness

The amount of deformation a screw shaft will experience axially under a load.

Tension Load

A load that generally stretches the ball screw.

These common ball screw terms to know will help you to select the right ball screw for your needs. Check out our inventory to purchase quality ball screw products, including assemblies and replacement parts.