To get the official, complete, and reliable standard, use these sources:
Pro Tip for Budget-Conscious Engineers: Look for "ISO 20457:2018 – Preview" on the ISO website. The free preview usually includes the scope, the first few pages, and crucially, the main tolerance table. For many internal design purposes, the preview table is sufficient, though you should buy the full standard for legal manufacturing contracts.
Subject: Dimensional Tolerances for Thermoplastics Pipes and Fittings Standard Reference: ISO 20457:2017 (Plastics pipes and fittings — Dimensions and tolerances)
The iso 20457 tolerance table pdf is more than a grid of numbers; it is a strategic tool for balancing cost and quality. By understanding the three tolerance classes (Fine, Medium, Coarse) and knowing how to navigate the linear and angular tables, you can produce drawings that are both professional and manufacturable.
To recap:
Keep a legitimate copy of ISO 20457:2018 on your digital shelf, and you will never again guess whether a "±0.5mm" is appropriate for a 2-meter-long part.
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
The ISO 20457 standard (formerly DIN 16742) defines the manufacturing tolerances and acceptance conditions for plastic molded parts. It is primarily used to align expectations between designers and manufacturers regarding dimensional accuracy in injection molding and other plastic processes. Key Tolerance Group: TG6
For general thermoplastics, the standard typically defaults to Tolerance Group 6 (TG6) unless otherwise specified.
Application: General tolerances (Series 1) apply to explicitly drawn dimensions that lack individual tolerance indications.
Typical Note: Engineering drawings often include the note: General tolerances ISO 20457 – TG6. ISO 20457 Tolerance Table Overview
The standard uses two main tables to determine the applicable tolerance: INTERNATIONAL STANDARD ISO 20457
ISO 20457 (and its German equivalent DIN 16742) is the international standard for dimensional and geometrical tolerances of plastic molded parts. It replaces older standards like DIN 16901 to provide a more consistent framework for injection molding and related processes. Key Tolerance Tables & TG Groups To get the official, complete, and reliable standard,
The standard classifies tolerances into Tolerance Groups (TG), typically ranging from TG1 to TG9. TG6 is the most common baseline for commercial plastic parts. Nominal Dimension (mm) TG4 (Precision) TG6 (General) TG8 (Coarse)
Values are approximate based on standard industry applications of ISO 20457/DIN 16742. How to Choose a Tolerance Group
Choosing the right TG depends on the material's shrinkage behavior and the part's functional requirements.
Material Family: Amorphous resins (e.g., ABS, PC) have lower shrinkage and can often achieve TG4 or TG5. Semi-crystalline resins (e.g., PA66, POM) have higher shrinkage and usually require TG6 or higher.
Production Difficulty: Tighter groups (TG1–TG3) are rarely used as they significantly increase mold costs and scrap rates.
Baseline Standard: Most engineering components default to TG6 unless specified otherwise for critical fitments like snap-fits. PDF Resources & Technical Guides Pro Tip for Budget-Conscious Engineers: Look for "ISO
You can access detailed guides and full tolerance tables through these technical document repositories:
PolTolerances Guide: A detailed 4-page overview of ISO 20457 and DIN 16742 including classification tables.
Standard Preview: An official abstract and sample pages of the ISO 20457:2018 Standard.
Engineering Guidelines: Practical application guides from manufacturers like OKW Gehäusesysteme showing how they apply TG6 to their thermoplastic products. PolTolerances en ISO-20457 (DIN 16742) - Scribd
If you are looking at a PDF of the standard, you will locate the relevant row based on the basic size of the component. You will then cross-reference that row with the column corresponding to the specific feature (e.g., shaft diameter vs. bore diameter). The result is a plus/minus value or a bilateral tolerance that defines the acceptable window of measurement.