The following are terms that are common in our trade. There have been few texts written on the subjects, so these represent a compilanion from balancing machine manufacturers and years of experience in this industry. These terms provide a common ground between us and our customers and are the shop practice of Cox and Sprague.

PLANE A preselected area around the part at right angle  to the axis where balance corrections can be made.

ANGLE The angle point around the plane where corrections are made.

COUPLE Two equal weights 180° apart but not in the same plane. This condition exists in varying amounts after single plane balancing correction are completed.

SPEED (RPM) Speed dose not enter into the balancing process. Balancing consists of adjusting the center of gravity to coincide with the mechanical center of the rotation of a part. Centrifugal force do increas with higher speeds but in a rigid part, the center of gravity dose not change (see graph). A rigid part is one that dose not change shape due to centrifugal forces (non-rigid part examples: rubber tires, long shafts that can 'whip, ' etc.).

TOLERANCE Normally expressed in ounce-inches (or metric measurements). The weight in ounce or fraction of an ounce is multiplied by the radius in inches. When no tolerance is specified, we balance to a point below where the weight of the part and its mechanical tolerance could be a factor.

DYNAMIC BALANCE This refers to running balance. A term used in earlier days to differentiate from static balance, and to indicate parts balanced by a machine. It is also used to indicate plane balancing.

STATIC BALANCE Balance accomplished on knife edges or rolls, where gravity rolls the heavy side to the lowest point where the correction is made.

SINGLE PLANE BALANCE When the part is a disc, is very narrow, or corrections in only one plane are possible, balancing machine can be set up to indicate only one plane. A couple may exist after balancing in this manner. The result is similar to static balancing in this manner. The result is similar to static balancing and may be completely satisfactory for the particular use of the part.

TWO PLANE BALANCE This is the ideal situation. Corrections are made in two preselected planes, spaced as far apart as possible. In this type of balancing, static and couple unbalance can be reduced to a minimum.

Tech Guide | Key Concepts | Terms | Quality Assurance