@RFPSteve this will certainly work for us and we'll be using it this way, but its a bit circuitous and unintelligent way to handle the callouts which should be integral part of the thread. This applies to holes as well. If this was done intelligently, suppose you were to make a D10 hole, with H7, then in CAM, you could change the post processor to automatically pull out a D9.8 drill, make the hole then a D10 reamer, all in one sequence. If it were just a D10 hole, with no tolerance, you'd call out a D10 drill and make the hole. Tapping would be more complex, but I'd suggest SiemensPLM to add two things, add a PMI box in the definition, where one could potentially choose the hole, tap, tolerances, and also pre-drill sizes that could be suggested based on the tolerance and also the possibility to add your own if you had some special requirement.