If your general tolerance block references "ISO 20457 – m", you do not need to write individual tolerances on every dimension. The machinist knows to adhere to the Medium tolerance table.
Before ISO 20457, many engineers relied on standards like Germany's to tolerance their plastic components. While useful, DIN 16901 was a national standard that lacked the global recognition needed for international trade.
Several industry sources confirm these general assignments. ISO 20457 TG4 is typically applied for precision injection molded parts such as gears, TG5 for housing parts, and TG6 for packaging components. In the automotive industry, critical components typically require TG4 or higher, with deviations measured in micrometers. iso 20457 tolerance table pdf
Understanding ISO 20457: The Definitive Guide to Plastic Molded Part Tolerances
The bridges this gap. It establishes standard tolerance blocks and surface profile criteria within a defined Geometrical Product Specification (GPS) datum framework. It helps stakeholders explicitly delineate between "general tolerances" (applied broadly to non-functional attributes) and "direct tolerances" (assigned to hyper-critical, tight-fit assembly dimensions). TOLERANCES If your general tolerance block references "ISO 20457
To standardize expectations between designers and molders, the International Organization for Standardization introduced . This standard replaces the older DIN 16742 standard and provides a robust framework for determining geometric tolerances and deviations.
The 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 While useful, DIN 16901 was a national standard
The standard provides general tolerances for linear dimensions, radii, angular dimensions, flatness, concentricity, roundness, and surface profile.
Before ISO 20457, many European-influenced toolmakers referenced , which defines tolerance groups based on part size and material shrinkage category. DIN 16901 classifies tolerances into Series 1 (Normal), Series 2 (Fine), and Series 3 (Precision). ISO 20457 expands this framework with nine tolerance grades (TG1–TG9), compared with the six tolerance groups in DIN 16901, providing greater granularity and international consistency.