"We sell trust," Mei said. "We sell parts that keep someone's machine running." Javier nodded; Mr. Owens thumped the bench with a palm. They decided to hold the line. Instead of racing to the bottom on price, they focused on value: traceability, documentation, faster turnaround, and the small but critical assembly testing they insisted on. They printed the tolerance table into their job sheets, used it to teach clients why a tighter fit mattered for longevity, and even offered tolerance-driven design advice to engineers who were used to outsourcing without oversight.
Master Guide to ISO 20457 Tolerance Tables for Plastic Molded Parts Direct Answer First
Angular tolerances are unique because the permissible deviation depends on the length of the shorter leg of the angle. The table provides deviations in degrees, minutes, or as a linear deviation per unit length (mm/m). A coarse tolerance for a 90° corner might permit ±1° for a very short leg, whereas the fine class could require ±0.5° or tighter. iso 20457 tolerance table pdf
Do not default to PT1. Interview your injection moulder first. Ask:
It establishes realistic dimensional tolerances based on material properties. It defines acceptance conditions for quality control. "We sell trust," Mei said
To properly reference this standard on your engineering prints or PDF drawings, you should include a specific note in the title block. Recommended Drawing Callout Format:
For each dimension on your drawing, determine whether it is: They decided to hold the line
Decide if your application requires Precision (TG1-TG4) or General (TG5-TG8) manufacturing.
If you are looking for a ready-made PDF of standard tolerance classes (fine, medium, coarse) with numerical values for linear dimensions, angles, or GD&T — you might be thinking of or ISO 286 .
This article serves as a guide to understanding the standard, finding an , and applying the correct tolerance groups for plastic injection molding projects. What is ISO 20457:2018?