| Term | Description | |------|-------------| | | Transition zone where the thread depth decreases to zero over a defined length. | | Thread undercut (relief groove) | A groove machined at the end of the threaded portion, allowing the thread to run out fully into a cylindrical or reduced-diameter relief. | | Full thread length | Portion of thread with complete profile (minor diameter). |
The DIN 76-A PDF document can be obtained from various sources:
The key takeaway is that . ISO 3508:1976 covered only thread run‑outs, and ISO 4755:1983 covered only undercuts for external threads. DIN 76‑1 covers both run‑outs and undercuts for both external and internal threads , making it a one‑stop reference for metric thread‑relief design.
Generally indicates a longer thread undercut/run-out, commonly used for standard screw production. din 76-a pdf
When a lathe or thread-rolling machine cuts an external thread up to a shoulder, the cutting tool cannot stop instantly. Without an undercut, a small zone of incomplete or imperfect threads forms near the shoulder, known as the .
Standardization documents are protected by copyright and generally must be purchased. You can find the full, current version of at these official retailers: DIN Media (Beuth Verlag): The Official DIN 76-1 Source . Accuris (formerly IHS): Offers DIN 76-1 PDF Downloads .
Properly dimensioned undercuts, including the specific rounding radii defined in the standard, help reduce notch effects and potential fatigue failure in highly stressed bolts. Comparison: Form A vs. Form B | Term | Description | |------|-------------| | |
is a technical standard from the German Institute for Standardization that specifies dimensions for thread run-outs (where the thread ends on a component) and thread undercuts
(Undercut Width): The total width of the groove, including the transition angles.
: If you have an M12 thread and require a standard external undercut, you point a leader line to the groove and label it: "Thread undercut DIN 76 – A" . | The DIN 76-A PDF document can be
: It allows the mating component (like a nut or a tapped plate) to screw down completely flush against the bolt shoulder.
Understanding this context is crucial for any professional working in an international environment, ensuring compliance with both global and German standards.