Iso 20457 Tolerance Table Pdf |top| Jun 2026

On a spring morning, as apprentices filed in and sunlight slanted through new windows, Ana handed a young machinist a fresh printout. "Learn this," she said. "But don't worship it. Use it to talk to people, to fix things, to make promises you can keep." The apprentice smiled and traced a column, feeling the same hush Ana had felt years before. Outside, delivery trucks rolled in and out. Inside, each tiny part they made slid into place within those invisible allowances, and the world—complicated, imprecise, human—ran a little smoother because someone had read the numbers and decided to make them mean something.

This table provides permissible deviations in millimeters for external sizes (shafts), internal sizes (holes), and features like step heights or radii. For a nominal size range (e.g., 0.5 mm up to 3000 mm), the table lists the upper and lower deviation limits for each class. For example, a 100 mm linear dimension under the “medium” class might show a tolerance of ±0.3 mm, while the “fine” class would show a tighter ±0.1 mm.

Note: For the exact breakdown across all groups (TG1–TG9) and specific material assignment matrixes, engineering teams must consult the official ISO 20457 PDF documentation.

Disclaimer: This article is for informational purposes. Always refer to the official ISO 20457:2018 document for legally binding tolerance values and definitions. iso 20457 tolerance table pdf

Imagine designing a gearbox. The gears inside require "Fine" tolerances, but the outer cast housing only needs "Coarse" tolerances. ISO 20457 provides a systematic way to assign these levels without over-specifying (which increases cost) or under-specifying (which causes assembly failure).

⚠️ These values are industry guidelines. For definitive figures, always refer to the official ISO 20457 standard.

Whether you are focusing on or quality control inspection . On a spring morning, as apprentices filed in

Note: These values are typical approximations for linear dimensions; refer to the official standard for the full matrix covering all dimensions and specific material groups. Selection Process

It applies specifically to , die castings, and similar processes. Unlike general machining tolerances, moulded parts have unique shrinkage, warpage, and draft angle requirements.

| Nominal Dimension (mm) | Tolerance (± mm) | |-------|-----------------| | up to 3 | ±0.07 | | 3–6 | ±0.12 | | 6–10 | ±0.18 | | 10–18 | ±0.22 | | 18–30 | ±0.26 | | 30–50 | ±0.31 | | 50–80 | ±0.37 | | 80–120 | ±0.57 | | 120–180 | ±0.80 | | 180–250 | ±0.93 | | 250–315 | ±1.05 | | 315–400 | ±1.15 | | 400–500 | ±1.25 | | 500–630 | ±1.40 | | 630–800 | ±1.60 | | 800–1000 | ±1.80 | Use it to talk to people, to fix

ISO 20457 represents a significant advancement in the standardization of plastic molded part tolerances. By providing a structured framework of tolerance grades (TG1–TG9), material shrinkage groups (SG1–SG5), and W/NW dimension classifications, the standard bridges the gap between theoretical design requirements and the practical realities of plastic manufacturing.

Historically, engineering documentation relied heavily on metal-machining tolerance standards like ISO 2768. However, polymers exhibit drastically different behaviors than metals, including massive thermal expansion, complex anisotropic shrinkage, and moisture absorption.

Dimensions influenced by moving components of the mold, such as the parting line between the core and cavity halves, sliders, lifters, or ejector pins. Because these parts shift slightly during clamping, they require wider tolerances (often shifted up by one tolerance group). 6. How to Implement ISO 20457 on Engineering Drawings

Make sure to verify the authenticity and accuracy of the PDF document before using it for design or manufacturing purposes.

Note: These are illustrative values — always refer to the full standard for critical applications.