Din 76a Pdf -

| Topic | Key Point | | --- | --- | | | DIN 76‑1: Thread run‑outs and thread undercuts — Part 1: For ISO metric threads in accordance with DIN 13‑1 | | Main purpose | Standardizes dimensions for thread run‑outs and undercuts on external and internal ISO metric threads | | Three forms | A (external, normal length – g₂ ₘₐₓ = 3.5 P) B (external, short design – g₂ ₘₐₓ = 2.5 P, special tools) C (internal) | | Comparison with ISO | DIN 76‑1 adds Form B and covers internal threads; ISO 3508/4755 do not cover internal threads | | Latest edition | DIN 76‑1:2025‑07 (includes correction for P = 5.5 mm radius value) | | CAD/CNC support | Integrated in PTC Creo, HEIDENHAIN, AutoCAD Mechanical, and many standard parts libraries | | How to obtain | Purchase official PDF from Beuth Verlag, DIN Media, Intertek Inform, ANSI, or NSAI |

When a thread is cut or rolled onto a cylindrical shaft, the cutting tool cannot stop instantly at a sharp 90-degree shoulder. This creates a "thread run-out"—a section of imperfect, shallow threads near the shoulder. din 76a pdf

For internal threads:

The primary purpose of a thread run-out or undercut is to provide a defined space at the end of a thread to ensure it can be machined or rolled to its full depth without interference from a shoulder or the bottom of a blind hole. If this space is not provided, the thread will be incomplete near the shoulder, preventing a nut or another part from seating flush against it. | Topic | Key Point | | ---