CNC machining accuracy, steel type selection, wear over time, and the integration of moving cores directly impact the tool-dependent ( ) tolerance limits.
Purchase the full ISO 20457:2018 from the International Organization for Standardization .
*This paper is a technical summary for educational purposes. For manufacturing, quality control, or legal compliance, you must purchase and reference the official, current version of the ISO 20457 standard document directly from iso 20457 tolerance table pdf
While the ISO 20457 tolerance table is a powerful tool, it is not a universal solution. The PDF document makes clear that general tolerances are default values. They apply only when no individual tolerance is specified. For features that require a precise fit (e.g., a bearing housing or a gear shaft center distance), the designer must still assign explicit, tighter tolerances. Furthermore, the standard does not cover every geometric characteristic—profile tolerances (for curved surfaces) are notably absent, as are tolerances for free-form surfaces.
The standard (which succeeded DIN 16742) provides a standardized framework for tolerances and acceptance conditions for plastic molded parts. It defines tolerance groups (TG) ranging from TG1 to TG9, where lower numbers indicate higher precision. For many standard industrial thermoplastics, TG6 is the commonly used baseline for general tolerances. Key Tolerance Tables and Documents CNC machining accuracy, steel type selection, wear over
Ranges (e.g., 0-30 mm, 30-100 mm) determine the base allowance.
The full table includes separate columns for: For manufacturing, quality control, or legal compliance, you
The (Tolerance Group 6) is a commonly used general tolerance for simple production settings. Below is the technical data for nominal dimension ranges (all values in mm) as referenced from sources like OKW Gehäusesysteme . Nominal Range (Over) W (Tool-Specific) NW (Non-Tool-Specific)
It is important to note that ISO standards are proprietary documents. While you may find snippets or summaries online, obtaining the official, complete generally requires purchasing the standard from:
The following table provides general capability ranges based on the part's nominal dimensions (size) and the selected tolerance grade: Nominal Dimension (mm) TG4 (Fine) TG5 (Medium) TG6 (Coarse) 1 to 3 mm 3 to 6 mm 6 to 10 mm 10 to 18 mm 18 to 30 mm 30 to 50 mm 50 to 80 mm 80 to 120 mm 120 to 180 mm 180 to 250 mm Critical Requirements for ISO 20457 Callouts