Using ISO standard mates can create a mismatch between the machined part 3D file and the component to be mounted. For example, if the surface of the gear set is modeled as "nominal size" as shown in Figure 3. This creates the possibility to machine the part to 142mm 0.025//0.025. This is especially true if the 3D file is modeled with a housing surface that is 142mm in diameter ("zero line" in Figure 3) and the shop uses the 3D file to program toolpaths. This scenario is shown in Figure 5.