Iso 8015 -

This sounds like a minor tweak, but it was a tectonic shift. Suddenly, the drawing had to say everything. No more silent assumptions. The result: clearer communication, but also a massive increase in the number of tolerances on every drawing.

Actually, the old default was the "Envelope Requirement" (Taylor Principle). ISO 8015 did something radical: It said that . That is, each specification on a drawing stands alone . A size tolerance does NOT control form unless explicitly stated. A flatness tolerance does NOT control parallelism unless explicitly stated. iso 8015

Then came a quiet revolution from Geneva, Switzerland. Its name was . The Old Way: The Silent Assumption Imagine a French aerospace company in 1985. An engineer drafts a simple shaft for a landing gear actuator. He specifies a diameter of ( 50 \pm 0.1 ) mm. He does not specify straightness, roundness, or parallelism. Why would he? The old default said: If no geometric tolerance is given, the size tolerance controls form . This was the Taylor Principle (or Envelope Requirement). The perfect virtual cylinder of the maximum material condition (MMC) would automatically limit how bent or oval the shaft could be. This sounds like a minor tweak, but it was a tectonic shift