If you have ever looked at a technical drawing and wondered, "Is that edge supposed to be sharp? How sharp is 'sharp'?" — you are not alone.
Disclaimer: This post is for informational purposes. Always refer to the latest official DIN ISO 13715 standard document for absolute compliance. din iso 13715
Simply put: It tells the machinist how to treat the "leftover" edges—those small intersections between two surfaces where no specific radius or chamfer is called out. If you have ever looked at a technical
Enter . This standard is the universal language for defining the condition of undefined edges on technical drawings. Always refer to the latest official DIN ISO
Let’s break down what it is, why it matters, and how to read its symbols. Officially titled "Technical product documentation — Indications for undefined edges," DIN ISO 13715 specifies how to indicate the permissible condition of edges that are not explicitly dimensioned elsewhere on the drawing.
For sharp edges that must cut (e.g., cutting tools, scrapers), write: "Edge max R 0.05" or "Sharp edge permitted – handle with care" (though the latter is rare in modern standards). The Most Common Mistake Do not write: "Break all sharp edges." This is subjective. Does "break" mean 0.1 mm or 1.0 mm? It depends on who is reading.
Here is what the symbols mean: