The standard applies to non-porous molded parts made from thermoplastics, thermoplastic elastomers, and thermosets. If agreed upon by contractual parties, the standard can also be applied to other plastic processes.
: Tolerances are assigned based on the nominal dimension of the part (e.g., < 1mm, 1–6mm, 6–30mm, etc.). Material Influence
Explicitly state the general tolerance rule. Example: General tolerances per ISO 20457 - TG6 .
It includes specifications for surface profiles, angular dimensions, and tool offsets (parting lines). OKW Gehäusesysteme Reference Documents & Tables
A true “tolerance table” in ISO 20457 depends on: iso 20457 tolerance table pdf
In manufacturing, "close enough" is rarely acceptable. Tolerance tables are the translation layer between a designer's intent and a machinist's execution. ISO 20457 tolerance tables are particularly important for several reasons:
On a spring morning, as apprentices filed in and sunlight slanted through new windows, Ana handed a young machinist a fresh printout. "Learn this," she said. "But don't worship it. Use it to talk to people, to fix things, to make promises you can keep." The apprentice smiled and traced a column, feeling the same hush Ana had felt years before. Outside, delivery trucks rolled in and out. Inside, each tiny part they made slid into place within those invisible allowances, and the world—complicated, imprecise, human—ran a little smoother because someone had read the numbers and decided to make them mean something.
Achieving a target tolerance grade is not just a matter of selecting a column on a PDF chart. The following variables heavily dictate real-world dimensional variance: Material Shrinkage ( VScap V sub cap S
To get the official, complete, and reliable standard, use these sources: The standard applies to non-porous molded parts made
Years later, Ana stood at the same bench where she'd first opened the old PDF. The shop had grown into a small factory with apprentices, CAD stations, and a quiet floor where machines hummed in coordinated rhythm. On the wall, framed under glass, was a clean reproduction of the tolerance table—this time accompanied by handwritten notes: material pairings, preferred surface finishes, and a list of clients who depended on that sheet for their lifetimes of service.
Plastics absorb moisture and expand or contract with temperature changes. ISO 20457 evaluates parts under standard climate conditions (typically 23°C and 50% relative humidity) after a specific storage period. How to Use the ISO 20457 Tolerance Table
Refers to dimensions affected by tool movement or parting lines. Key Concepts of ISO 20457
By understanding and correctly applying the ISO 20457 tolerance table, you will design parts that are not only functional but also economically producible—saving time, reducing costs, and ensuring customer satisfaction. Example: General tolerances per ISO 20457 - TG6
Word spread the way things do in small towns: through a customer with a recommendation, an apprentice who saw the coupling run smoother than anything they'd seen in months. Orders returned—one-off repairs at first, then short runs for local manufacturers who needed a nimble supplier. People liked that Ana could promise tolerances and deliver parts that met them. They liked that she paid attention to the subtle language of standards. The ISO 20457 table, once just a relic, became the backbone of her shop's revival.
Each table uses the four tolerance classes, allowing a designer to scale the precision to the functional needs of the part.
If no individual tolerance is specified on a drawing, the standard applies "general tolerances" based on the selected TG to ensure all features are controlled. Factors Affecting Tolerance Selection