In the world of injection-molded plastic components, a frequent source of friction between designers and manufacturers is surface quality. Designers demand "perfect" parts, while production managers speak in microns and shrinkage rates. The German standard DIN 16742 bridges this gap. At its peak sits TG5—the highest tolerance grade for surface finish and geometry.
TG5 stands for Tolerance Group 5. The tolerance groups in DIN 16742 are generally arranged by precision level:
DIN 16742 is a standard that specifically deals with tool holders and their interfaces. Tool holders are essential components in machine tools, serving as the bridge between the machine and the cutting tool. They are critical in ensuring that the cutting tool is accurately positioned and securely held during the machining process. The standard covers various aspects, including dimensions, materials, and performance requirements for tool holders.
The selection of TG5 is typically driven by the material choice and the part geometry. din 16742 - tg5
TG5 is the most practically applicable "fine" grade for serial production. It is often misunderstood as "the best possible," but in reality, it represents the optimal balance between precision and manufacturability.
1. Dimensional Tolerances Under TG5, a 100 mm nominal dimension on a non-critical feature allows a deviation of approximately ±0.2 mm to ±0.3 mm, depending on the material (amorphous vs. semi-crystalline). For reference, TG1 would allow ±0.8 mm at the same length.
2. Surface Structure (The "5" in TG5) The standard strictly defines surface roughness based on comparator blocks. TG5 requires surfaces to be free from visible sink marks, flow lines, and ejector pin marks that exceed a depth of 0.02 mm. It aligns roughly with Rz 10–20 µm (average maximum height of the profile). In the world of injection-molded plastic components, a
3. Form and Position TG5 enforces flatness, roundness, and parallelism. A TG5 part cannot simply have the right width; its side walls must be straight within 0.1 mm over 100 mm.
DIN 16742 is the German standard for Tolerances for injection-molded plastic parts. It replaced older standards like DIN 16901. It provides a systematic way to define allowable deviations in dimensions, geometry, and surface for thermoplastics, thermosets, and elastomers.
The standard defines several tolerance groups (TG) – from TG1 (very fine/precision) to TG7 (very coarse). DIN 16742 is a critical German standard that
TG5 sits in the middle, representing normal industrial precision for injection molding without special tooling or process controls. It is the most commonly specified tolerance grade for functional plastic parts.
DIN 16742 is a critical German standard that defines tolerances and dimensions for molded plastic parts. In the field of injection molding and polymer engineering, achieving exact dimensions is challenging due to material shrinkage, warpage, and process variations. DIN 16742 provides a systematic framework for designers and manufacturers to agree on acceptable dimensional deviations.
Within this standard, dimensions are categorized into specific Tolerance Groups (Toleranzgruppen). TG5 (Tolerance Group 5) represents a specific tier of precision that balances manufacturing feasibility with functional requirements.