Pdf: Iso 20457 Tolerance Table

The ISO 20457 standard, which replaces the older DIN 16742, is the primary international guideline for determining tolerances of plastic molded parts. Unlike metal components, plastic parts undergo significant shrinkage and environmental changes, making standard rigid-body tolerance chains (like ISO 286) often unsuitable. Core Tolerance System (Tolerance Groups)

• Group 1: Materials with low shrinkage (e.g., PVC-U, PVC-C).
• Group 2: Materials with higher shrinkage (e.g., PE, PP, PVDF).
• Group 3: Specific materials requiring special consideration (e.g., PE-X).

• Misreading upper vs. lower deviation signs or confusing unilateral vs. bilateral tolerances.
• Applying tabulated size tolerances to features that require form/flatness/position controls.
• Ignoring environmental measurement conditions (temperature) that shift measured dimensions.
• Treating the table as one-size-fits-all without accounting for material/process limitations or assembly stack-ups.

The standard provides a framework for specifying tolerances that balance the need for precision with the practical limitations of manufacturing processes. iso 20457 tolerance table pdf

The Structure of the Tolerance Tables

The core of the standard lies in its tabulated data, organized into four tolerance classes: fine (f), medium (m), coarse (c), and very coarse (v). The tables are not a single monolithic grid but are separated by the type of geometrical characteristic. The key tables within the ISO 20457 PDF document typically include: The ISO 20457 standard, which replaces the older

Shrinkage: Unlike metal standards, ISO 20457 accounts for the molding compound properties and how they shrink during cooling. Group 1: Materials with low shrinkage (e