To find a specific tolerance value, users follow a multi-step process often detailed in reference PDFs: Identify Material : Determine the specific plastic being molded. Determine Category : Look up the material in a provided table to find its Tolerance Category based on shrinkage. Select Tolerance Grade

If specific functional features (like a snap-fit or a bearing housing) require tighter tolerances than the rest of the part, call them out directly next to the dimension (e.g., 12.5 ±0.07 for a TG3 feature), while letting the rest of the part default to the general TG6 specification. 7. How to Download the Official ISO 20457 PDF

Always confirm that the table shows and includes the separate columns for parting line (typically labelled “F” for “flash line” in German-influenced documents).

Best Practices for Specifying ISO 20457 on Engineering Drawings

Below is a simplified reference table mapping the nominal dimensions (mm) against standard Tolerance Grades (TG) for Series W (Tool-Dependent) dimensions. Note: All values below are in millimeters ( ± mmplus or minus mm

The Ultimate Guide to the ISO 20457 Tolerance Table for Plastic Molded Parts

Note: This table represents general dimensional tolerances. For exact allocations based on specific compound shrinkage rates and tool-bound vs. non-tool-bound dimensions, please reference the official ISO 20457 PDF framework. 5. Tool-Bound vs. Non-Tool-Bound Dimensions

The standard helps engineers move away from arbitrary "general tolerances" (like ±0.1mm across the board) and instead use scientifically backed limits based on material properties and manufacturing capabilities. Key Factors Determining Plastic Tolerances

The standard uses a tiered system to assign tolerance groups (TG) based on the material's complexity and the required precision:

High-shrinkage raw polymers or flexible elastomeric components. The Structure of the ISO 20457 Tolerance Table

What (e.g., ABS, Polycarbonate, Nylon) are you using?