When difficult part features need to be qualified a coordinate measuring machine (CMM) can be the answer for an awkward problem. If those features are external threads, there are a number of options available to obtain measurements besides a CMM. However, if internal threads are involved, a CMM is often chosen for the job but may be physically limited due to the size of the probe needed to get into smaller threads, but is still useful despite this limitation.

The cost of large fixed limit gages often inspires manufacturers to use their CMM to save this expense until the customer rejects parts using his fixed limit gages. Sadly, all is not sweetness and light when conflicts arise between fixed limit gaging and CMM measurements. It becomes a battle of the hardware where a machine costing say, over thirty thousand dollars, is up against a not-so-flashy-looking plug or ring gage worth a few hundred dollars.