To understand ISO 8015, one must first understand the traditional Envelope Principle. Under this older rule, a single size tolerance for a shaft or hole implicitly controlled its form. For example, a shaft specified as 10±0.1 mm must not only measure between 9.9 and 10.1 mm at any cross-section, but it must also fit within an imaginary perfect envelope of 10.1 mm. This meant the shaft could not be banana-shaped or lobed beyond that envelope. While simple, this principle is often unnecessarily restrictive. For a feature that does not need to assemble with a mating part of perfect form, enforcing the envelope imposes costly grinding or finishing operations on features that could otherwise be produced via efficient turning or molding.
ISO 8015 is a fundamental international standard in Geometrical Product Specifications (GPS) that establishes the . In the world of precision manufacturing, this standard dictates how dimensional and geometrical tolerances relate to one another on technical drawings. 1. The Core Principle: Independency iso 8015 tolerance
A linear tolerance (size) only controls the local actual sizes (two-point measurements). To understand ISO 8015, one must first understand
The defining feature of ISO 8015 is the . According to this rule: This meant the shaft could not be banana-shaped
0.1 mm) only controls the actual local size of a feature (measured at two points) and does control form deviations like straightness, circularity, or flatness.
Before this standard became the global norm, many regional standards assumed a link between size and form (for example, if a hole's diameter was within tolerance, its roundness was assumed to be somewhat controlled by that same limit). Under ISO 8015: