DIN 76-A designates the standard ("normal") design for thread run-outs and undercuts for metric ISO threads, ensuring proper seating for external threads. It provides essential tool clearance and reduces stress concentrations, featuring a specific undercut width and radius for precision engineering applications. To review the technical specifications, you can find the DIN 76-1 standard on or through ANSI Webstore BAER Tools Thread Relief Explained: Function, DIN 76 & Practical Use
Since you need the data now, here are the standard undercut widths for metric threads (P = Pitch):
Disclaimer: This post is for informational purposes. Always purchase the official standard for legal manufacturing compliance. din 76-a pdf
| Thread size (M) | Pitch P (mm) | Undercut width a (mm) | Undercut depth t (mm) | |----------------|--------------|------------------------|------------------------| | M3 | 0.5 | 0.8 | 0.15 | | M4 | 0.7 | 1.0 | 0.20 | | M5 | 0.8 | 1.2 | 0.25 | | M6 | 1.0 | 1.5 | 0.30 | | M8 | 1.25 | 1.8 | 0.35 | | M10 | 1.5 | 2.0 | 0.40 | | M12 | 1.75 | 2.5 | 0.50 | | M16 | 2.0 | 3.0 | 0.60 |
Form A is typically preferred; Form B is a "short" version used only in special cases where space is limited. BAER Tools Accessing the PDF DIN 76-A designates the standard ("normal") design for
How to get the DIN 76-1 PDF (Legally)
DIN 76 is divided into three parts. Part 1 covers metric threads, where the "Form" designations are categorized as follows: It might refer to Shape A (Type A)
Final Recommendation: If you are a student or hobbyist, a summary table from a textbook will suffice for learning. But if you are a professional engineer or a manufacturing shop, purchase the official DIN 76-1:2016-10 and DIN 76-2:1990-03 PDFs from Beuth Verlag. Consider it a small investment in quality and legal safety.