ISO 21920 replaces ISO 1302 / 4287 / 4288
The three-part ISO 21920 (published December 2021) replaces the earlier surface texture indication, profile parameter and decision rule standards. Drawings issued before it stay bound to the older standards.
A drawing with the older ISO 1302 symbol takes its parameters from ISO 4287, a drawing with the newer root symbol from ISO 21920. Check which one applies before comparing roughness numbers across drawings.
General shop guidance in our own words. The drawing and the standard it cites decide; verify on a sample part.
Tell the advisor the feature, the tolerance on the drawing and the material. It answers with machining choices, brand-neutral.
Definition written in our own words and checked against digitalsurf.com. Symbol and term names follow ISO 21920; we do not reproduce standard text. See the full index.