IT Grade

Description

IT Grade refers to the International Tolerance Grade of an industrial process defined in ISO 286. This grade identifies what tolerances a given process can produce for a given dimension.

The specific Tolerance for a particular IT grade is calculated via the formula shown here.

An industrial process has an IT Grade associated with, indicating how precise it is. When designing a part, an engineer will typically determine a key dimension (D) and some tolerance (T) on that dimension. Using this formula, the engineer can determine what IT Grade is necessary to produce the part with those specifications. Thus, if injection molding has an IT Grade of 13 and a part needs an IT Grade of 5, one cannot injection mold that part to those specifications. It is useful in determining the processes capable of producing parts to the needed specification.

Related formulas

Variables

Ttolerance in micrometres (dimensionless)
ITGIT Grade, a positive integer (dimensionless)
Dgeometric mean dimension in millimeters (dimensionless)