Iso 20457 Tolerance: Table Pdf

Angles are treated differently because the deviation is measured as a length over a given length (mm/m) or directly in degrees/minutes.

Standard measurement temperature (usually 23°C) and humidity (50% RH).

Plastics shrink as they cool. Amorphous materials (like Polycarbonate) shrink evenly, while semi-crystalline materials (like Polypropylene) or glass-filled polymers shrink unevenly (anisotropy). ISO 20457 classifies materials into specific groups based on their processing shrinkage variance. 2. Evaluation Level (Production Accuracy) iso 20457 tolerance table pdf

| Tolerance Class | Permissible Deviation (mm per 100mm length) | | :--- | :--- | | Fine (f) | ± 0.3 mm/m | | Medium (m) | ± 0.5 mm/m | | Coarse (c) | ± 1.0 mm/m |

: The industry standard for most technical plastic parts with moderate fit requirements. Class C (Low Precision) Angles are treated differently because the deviation is

Note: Unlike outside diameters, wall thickness usually has bilateral tolerances ($\pm$).

Note: This table is a representative summary. The official ISO 20457 PDF contains exact values and footnotes regarding chamfers, radii, and external/internal dimensions. Evaluation Level (Production Accuracy) | Tolerance Class |

AG=AW2+AP2cap A sub cap G equals the square root of cap A sub cap W squared plus cap A sub cap P squared end-root How to Implement ISO 20457 on Technical Drawings

Unlike metal fabrication, plastic injection molding relies on raw material behavior, part geometry, tool construction, and process variables. ISO 20457 categorizes these dynamics into nine designated , representing a spectrum from extreme high-precision to general-purpose molding.

For multi-component molded parts (e.g., overmolded or two-shot components), the tolerance grade must be determined for each material separately and specified as distinct general tolerances. For example, a hard component may be specified to TG5 while a soft component (elastomer) is specified to TG7.

: Thermoplastics and thermosets shrink between 0.5% and 2.5% during cooling.