The cause of the problems with dimensional tolerancing in one picture

Although you may think your dimensional tolerances are arranged in a coordinate system, on a real component they are not. The component above can meet all the dimensional tolerances, while having significant, unpredictable deviations.

With this type of tolerancing, your supplier will not know which angular relationships are important and have to be maintained and which are less important. The result is that he either try to maintain them all and make the component more expensive than necessary, none of them, in which case the component is unlikely to function, or he will try to guess which ones are important and probably guess wrong. In any case, it is not your supplier's responsibility, if the component does not work (as long as he meets the dimensional tolerances).

When you try to limit these deviations with geometrical tolerances one by one, as you detect them in production, you have hybrid tolerancing.

Henrik S. Nielsen