While DIN 16901 is still referenced for legacy parts, .
Lower TG numbers (e.g., TG1–TG4) represent high-precision requirements.
Read the corresponding plus/minus ( ±plus or minus ) value in millimeters. Simplified ISO 20457 Tolerance Lookup iso 20457 tolerance table pdf
ISO 20457 Tolerance Table PDF: Comprehensive Guide to Plastic Injection Molding Tolerances
Understanding where ISO 20457 fits in the standards landscape helps justify its use to colleagues. While DIN 16901 is still referenced for legacy parts,
In North America, the SPI tolerance system—using letter-number grades such as A1 (commercial) through B3 (fine)—remains common. SPI tolerances are expressed as a base tolerance plus an increment per inch of dimension. A B1 tolerance on a 2-inch PP dimension yields approximately ±0.010 inches (0.254 mm). Many Chinese manufacturers familiar with European standards can map SPI specifications to ISO 20457 grades. To avoid misunderstandings when sourcing from offshore suppliers, specify ISO 20457 TG grades directly rather than relying on SPI conversion.
The full standard contains complex tables, but they are structured based on: Simplified ISO 20457 Tolerance Lookup ISO 20457 Tolerance
By using the ISO 20457 tolerance table, engineers and manufacturers can:
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