Here is a short "technical story" to explain why this standard exists and how it works. The Problem: The "Vanishing" Thread
While many versions (like the 1983 edition) are superseded, the latest active versions are often cited in technical manuals for fastener precision, such as the 2016-08 revision. din 76a pdf
Official copies of are copyrighted and must be purchased through authorized standards organizations: Beuth Verlag : The official distributor for DIN standards. Here is a short "technical story" to explain
DIN 76 is a German industrial standard divided into multiple parts, primarily focusing on how a thread terminates. DIN 76 is a German industrial standard divided
As a rule of thumb, the undercut diameter should be slightly smaller than the minor diameter of the thread to ensure the mating part passes over it freely. Where to Find the DIN 76-1 PDF