As a practical example: for an thread (pitch 1.5 mm), a DIN 76‑A undercut would have an undercut diameter of approximately 2.3 mm (relative to the thread core), a length of about 5.2 mm, and a transition radius of 0.8 mm.
Grading rubric (brief)
This document applies to both external threads (e.g., on bolts and threaded studs) and internal threads (e.g., in blind tapped holes) that use ISO metric coarse or fine pitch threads [9†L3-L6] [10†L7-L8].
Without a DIN 76-A undercut, a matching female component (like a nut or a tapped hole) cannot seat flush against the shoulder, leading to weak joints and assembly failures. Geometric Features of DIN 76-A din 76-a pdf
To help you get the exact data you need, could you clarify if you are looking for the dimensions of a (like M8 or M12)? I can also provide the details for Form C (internal threads) if your project involves tapped holes. Share public link
To help me provide more specific information, could you share if you are looking to , or do you need to calculate the exact tolerances for a specific thread size ? Share public link
Some university libraries and technical portals provide to DIN standards for students and faculty. For example, the TU Darmstadt CAD tutorial includes a direct link to the Perinorm portal, where authorized users can view DIN 76‑1 online. As a practical example: for an thread (pitch 1
What (e.g., M10, M20) are you working with? Are you designing for high-fatigue load applications? Do you need the measurements in metric or inch conversions ? Share public link
An undercut matching DIN 76-A removes this imperfect thread area. It serves several crucial functions:
It is worth noting that the earlier ISO standard specified a single undercut length of only ( 3P ). German industry found that ( 3P ) was not sufficient to produce a clean thread using conventional tools, so DIN 76‑1 retained ( 3.5P ) as the normal design. This is a classic example of a national standard going beyond the international baseline to reflect real‑world manufacturing practice. Geometric Features of DIN 76-A To help you
In modern CAD environments (such as SolidWorks, Autodesk Inventor, or PTC Creo), you do not need to manually model the intricate geometries of the undercut unless required for specific CAM simulations.
For most applications, the is the one to use. However, if you are maintaining legacy products that were qualified against the 1983 edition, it is wise to compare both documents before making changes.