As we consider the possibility that products can be manufactured anywhere in the world, we must also think about the specifics of the standard we use to describe the product requirements.
Much has been written about the advantages of Geometric Dimensioning and Tolerancing (GD&T), and much of it is true. By explicitly describing datum systems and zones to control the allowable variability of the part characteristics, many of the ambiguities that arise from limit tolerances on dimensions are overcome. GD&T has been growing steadily in acceptance since its introduction in the 1950s with MILSTD8 (actually, the Ordnance Corps ORD 30-1-7 appeared in 1946, and also described dimensioning and tolerancing). One of the benefits of GD&T is that the requirements are captured in symbols, rather than notes, so a design can be manufactured to the specifications regardless of the native language at the manufacturing facility. As we consider the possibility that products can be manufactured anywhere in the world, we must also think about the specifics of the standard we use to describe the product requirements.
The current ASME standard for GD&T is ASME Y14.5-2009; this standard is developed by subcommittee 5 of the ASME standards committee Y14 Engineering Product Definition and Related Documentation Practices. The Y14.5 standard enjoys a large circulation and sales worldwide, so it can truly be thought of in international terms. However, there are other standards for GD&T, specifically those produced by ISO technical committee 213 Dimensional and geometrical product specifications and verification. How can we be sure that the manufacturer of our product will have sufficient training in the ASME GD&T? If we are part of an international company, will all of our sites be using the same standards for GD&T when they develop designs or produce products? And finally, are the ASME and ISO standards really that different anyway?