#### True Position Tolerancing

True Position Tolerancing is one of three possible tolerancing types for Target Plots. It also is the default tolerancing type for the first Target Plot you create. This type of tolerancing requires that certain data exist in the database. See "Chart Display - Target Plot" for information on changing the tolerancing used.

Data Requirements for True Position Tolerancing

For true position tolerancing, three variables must be reported for the feature: two dimensional variables that correspond to the reference plane for the plot, and one .T variable, which is the true position tolerance variable. The true position tolerance variable must have a .T extension. It is not necessary, however, to have data values for the .T variable; only a variable record that defines an upper tolerance is necessary. If the T. variable does not exist in the database, the default tolerance defined through the Chart Display Options/Target Chart from the Options menu will be used (if no default tolerance or .T variable exists, the plot will be created, but will display “No Valid Data” - refer to the note below). The nominal must be defined as 0.0 and the true position tolerance must be the upper tolerance. The lower tolerance should be zero.

For example, if the feature is CIRCLE1. and the reference plane is XY, the two dimensional variables would be CIRCLE1.X and CIRCLE1.Y, and the true position variable would be CIRCLE1.T. Variables CIRCLE1.X and CIRCLE1.Y must have data associated with them; CIRCLE1.T requires only an upper tolerance definition.

Note: If you are creating your first Target Plot and the .T variable does not exist in the database, you can just create a plot anyway (it will display “No Valid Data”), and set your configure options later, or you can use the Data Editor tab to create or rename the .T variable, and then create the plot.

See also:

- Chart Display - Target Plot

- Target Individual Chart

- Target Group Chart

- Elliptical Tolerancing

- Rectangular Tolerancing

- T Variable