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Published by the German Institute for Standardization (DIN), outlines the limits of deviations for linear and angular dimensions of molded plastic parts. It replaced the older DIN 16901 standard to align directly with modern international ISO standard networks.
In this standard, stands for Tolerance Group . The standard defines nine groups (TG1 through TG9), where lower numbers represent tighter, more expensive precision, and higher numbers represent looser, more economical tolerances.
Dimensional tolerances depend on the (mm) of the feature. Below is a simplified table for TG5 (based on DIN 16742, general tolerances for non-critical dimensions): din 16742 - tg5
Standard testing conditions also need to be specified. According to DIN EN ISO 291, the reference atmosphere for measurement of plastic moulded parts is and 50 % ± 10 % relative humidity . Parts should be conditioned and measured under these conditions to obtain repeatable results. A typical notation in the drawing label field would read:
Standard industrial and commercial manufacturing profiles. Published by the German Institute for Standardization (DIN),
: It is often specified for "hard" plastic components or multi-component parts where a more accurate fit is needed (e.g., snap-fits or bearing housings). Cost vs. Accuracy
The selection of a tolerance group is not arbitrary. The standard provides a structured, point-based scoring system that evaluates five individual influence factors. The sum of these points directly determines which TG is achievable for a given part in a given production environment. Those five factors are: The standard defines nine groups (TG1 through TG9),
A very specific request!
| Feature | TG4 (Fine) | TG5 (Very Fine / Precision) | | :--- | :--- | :--- | | | Standard precision | High precision | | Mold cost | Moderate | High (requires hardened steel, 3+ slides) | | Typical application | Snap-fits, enclosures | Gears, bearings, optical housings | | Process window | Wide | Very narrow (requires dry resin, controlled environment) |
is the specific high-accuracy tolerance group under the German engineering standard for plastic injection molded components, prescribing structural dimensions and production deviations. Unlike metal fabrication, where uniform standard tolerances like ISO 2768-mk apply globally, plastic injection molding undergoes dynamic changes due to processing shrinkage, material properties, and mold architecture. Selecting TG5 indicates a demand for precision-level engineering tolerances , typically designated for standard high-end injection molding applications where functional fit is essential. Understanding the DIN 16742 Framework
The standard sets out a systematic approach to assigning meaningful, production-feasible tolerances based on material properties, process characteristics, part geometry, and quality requirements. At the core of this system are nine tolerance groups (TG1 through TG9), with occupying a central position as the standard tolerance group for conventional injection moulding.