GD&T Tutorials 03 : Dimensions and Tolerances

GD&T Tutorials : Dimensions and Tolerances

Dimension [1.3.22]: is a numerical value or mathematical expression in appropriate units of measure used to define the size, location, orientation or form of a feature or feature of size.

Tolerance [1.3.60]: is the total amount that a specific dimension is permitted to vary. It is the difference between the maximum and minimum limit.

Nominal Size [1.3.56]: is the designation used for the purpose of general identification.

Limit Tolerance Dimensioning [1.3.55]: is where a dimension has its maximum and minimum limit stated. In limit dimensioning, the maximum value is placed on the top and minimum value is placed on the bottom.

Plus / Minus Tolerancing: is where the nominal size is specified first, followed by a plus/minus value of a tolerance.

Bilateral Tolerance [1.3.61]: is one that allows the dimension to vary in both directions from the specified nominal size.

Equal Bilateral Tolerance: is where the allowable variation from the specified nominal size is same in both the directions.

Unequal Bilateral Tolerance: is where the allowable variation from the specified nominal size is not same in both the directions.

Unilateral Tolerance [1.3.63]: is where the allowable variation from the specified nominal size is all in one direction.

Basic Dimension [1.3.23]: is a numerical value used to describe the theoretically exact size, true profile, true position or orientation of a feature or a feature of size

Reference Dimension [1.3.24]: is a dimension used for information purposes only. It is a repeat dimension or is derived from other values shown on the drawing or on related drawings.