Glossary Balancing Technology

Balance quality grade

Possibility to classify rigid rotors; product from mass eccentricity and angular velocity at service speed or trajectory speed of the center of mass each in mm/s (refer also to ISO 21940-11).

Balance tolerance, maximum permissible residual unbalance

The amount of unbalance (with respect to a measuring or correction plane) that is specified as the maximum below which the state of unbalance is considered acceptable.


Procedure during which the mass distribution of a rotor is checked and typically is corrected to ensure that the residual unbalances, the vibration of the journals, the forces on the bearings and/or the bearing vibrations at service speed or for a speed range are within specified limits.

Balancing bearings

For example rolling element bearings with reduced clearance to support rotors from aero-engines in a low-speed balancing machine.

Balancing machine

A machine that provides a measure of unbalance in a rotor, and that can be used for adjusting the mass distribution of that rotor to reduce the unbalance.

Balancing machine sensitivity

Resolution of the unbalance display of a balancing machine.

Balancing putty

Putty normally used to add a test mass to a rotor during balancing.

Balancing run

Cycle consisting of one measuring run and the successive unbalance correction.

Balancing speed

Speed at which the rotor is being balanced.

Bearing support or work support

Component of a balancing machine containing the rotor support, which attaches to the machine bed.

Belt drive

In a balancing machine, a mechanical drive consisting of a motor, belt, pulleys and belt tensioner. Diameter of motor pulley and driven rotor diameter should not be close in order to avoid the generation of phantom unbalances.

Bob weight

Mass attached to the crank pins of a crankshaft to simulate a portion of the rotating and oscillating mass of piston and rod during balancing.

Bode plot

With balancing the amount and angle of vibration at shaft speed or twice the shaft speed plotted against running speed.