Air Motor Terms

The terms listed on this page are commonly used when describing air motor tools and their performance characteristics. These expressions are widely referenced by manufacturers, engineers, suppliers, and end users across the industry. While some terms are used interchangeably, others have specific technical meanings that can affect how an air motor is selected, specified, or applied. This glossary is provided to help clarify commonly used air motor terminology and support a better understanding of product specifications and technical discussions.

Air Consumption: This is the volume of compressed air that a motor uses at it’s nominal speed and at a specified air pressure. Commonly measured in cubic feet per minute (cfm).

Axial Load: The force that is applied in the same direction as the spindle. Exceeding the manufacturer’s specified maximum load will reduce the lifetime of the bearings and possibly the motor.

Idle Speed: The speed that a motor will run at when there is no load and sufficient air flow. Measured in rpm.

Nominal Power: Nominal Power is the maximum power produced by the motor at a specified air pressure. It is normally measured at half the idle speed. Measured in watts (W) or horsepower (HP).

Nominal Speed: The motor speed where the motor reaches its maximum power. This is normally half of the idle speed and is measured in rpm.

Nominal Torque: The torque produced at the maximum power of the motor or at half the idle speed. This is measured in Nm.

Power: Is a measure of the amount of work done per second. The faster and the higher the torque - the more power is produced. An air motor will produce a different amount of power depending on the load that is applied to it. Power is measured in watts (W) or horsepower (HP). The power of a pneumatic motor peaks at half it's idle speed (Nominal Speed).

Radial Load: The force that is applied perpendicular to the spindle. This is measured at a certain point on the spindle. Exceeding the manufacturer’s specified maximum load will reduce the lifetime of the bearings and possibly the motor.

Stall Torque: The torque that a motor produces just before it stops when it is slowly braked. This can be anywhere between 1.5 and 2 times the Nominal Torque

Start Torque: The torque that a motor produces at start up. This torque varies depending on the vane position and should be quoted as the minimum guaranteed start torque. The start torque can be between the nominal torque up to 1.5 times the nominal torque.

Torque: The turning force of the motor. Torque (Nm) = Force (N) x Distance from the turning point (m). 9.8Nm will balance a 1kg weight on a 1 meter radius reel.