Geometric tolerances (GTOLs) provide a comprehensive method of specifying where on a part the critical surfaces are, how they relate to one another, and how the part must be inspected to determine if it is acceptable.

They provide a method for controlling the location, form, profile, orientation, and run out of features. When you store a Creo Parametric GTOL in a solid model, it contains parametric references to the geometry or feature it controls—its reference entity—and parametric references to referenced datums and axes. As a result, Creo Parametric updates a GTOL’s display when you rename a referenced datum.

In Assembly mode, you can create a GTOL in a subassembly or a part. A GTOL that you create in Part or Assembly mode automatically belongs to the part or assembly that occupies the window; however, the GTOL can refer only to datum feature symbols belonging to that model itself, or to components within it. It cannot refer to datum feature symbols outside of its model in some encompassing assembly, unlike assembly created features.

You can add model owned GTOLs in Part or Drawing mode, but they are reflected in all other modes. Creo Parametric treats them as annotations, and they are always associated with the model. Unlike dimensional tolerances, though, GTOLs do not affect part geometry.

When adding a GTOL to the model, you can attach it to an edge, an existing dimension, elbow of an existing note, or an existing GTOL, as well as display it as a note without a leader. You can also attach GTOLs to designated areas.

When you place a new GTOL, Creo Parametric automatically creates two parameters for each tolerance value that you specify while creating that GTOL. One parameter is stored as a real number and the other as a string. You can edit the value of the real number using the Parameters dialog box that opens when you click Tools > Parameters. However, you cannot edit the value of the string type of parameter. Creo Parametric also creates some default parameters; however, these parameters are not editable.

When you place a GTOL on an annotation, the owner of the GTOL changes to the owner of the annotation it is placed on. For example, in an assembly, if you place an assembly-owned GTOL on a part-owned dimension, the GTOL becomes a part-owned GTOL. This is also applicable if you place the GTOL on the witness line of that dimension.