While Leo usually uses (the standard "long" version), the DIN 76-1 standard offers others for different scenarios:
Use specialized grooving inserts that natively match the required transition radius (
Choosing between a DIN 76-A undercut and a standard thread run-out involves a trade-off between strength and assembly requirements:
What specific (e.g., M8, M16) or pitch you are working with? din 76a pdf
: Fasteners with a thread undercut do not meet the minimum breaking load requirements specified in DIN EN ISO 898-1 Accessing the PDF and Papers
The DIN 76a standard (officially DIN 76-1) is a cornerstone of modern mechanical engineering. It ensures that threaded components are not only manufacturable but also reliable and safe to assemble. By providing a clear, mathematically defined system for thread run-outs and undercuts, it bridges the gap between design intent and manufacturing reality.
To safely integrate these measurements into CAD software (like SolidWorks, AutoCAD, or Fusion) or to program CNC lathes, it is always recommended to reference the official, authoritative technical documents. While Leo usually uses (the standard "long" version),
Do you need help calculating ?
If you are looking to download or purchase the official , it is highly recommended to obtain it through authorized standards distributors like Beuth Verlag or the ISO Store to ensure you are utilizing the most current, uncorrupted version of the DIN 76-1 framework.
) : The curvature radius linking the undercut to the unthreaded shaft to prevent stress risers. Standard DIN 76-A Dimension Table Reference By providing a clear, mathematically defined system for
For external threads, the standard defines the shape and length of the thread run‑out, i.e., the region where the thread profile gradually fades out. This zone avoids a sharp stress‑raising step at the end of the thread, improving the fatigue life of the fastener. For internal threads in blind holes, the standard defines the minimum length of the thread run‑out at the bottom of the hole, ensuring that the full thread can be produced without crashing the tap.
: Applies specifically to ISO metric threads (coarse and fine pitch) as defined in DIN 13-1.
This distinction does not exist in the source international standards. ISO 4755:1983 specifies a single type with g₂ max = 3 P , which German experts found insufficient for reliable production with conventional tools. Consequently, DIN 76‑1 adopted the more practical 3.5 P for normal use while retaining a short version for special cases.
: Specifies Standard thread undercuts for external (male) threads.
When designing or manufacturing threaded components, ensuring proper fit and assembly is critical. One often overlooked but vital element of thread design is the thread undercut, standardized under .