In some modern contexts, ISO standards are superseding DIN, though DIN 76 remains the industry favorite in Europe.
DIN 76-1: Thread run-outs and thread undercuts for ISO metric threads
Understanding this context is crucial for any professional working in an international environment, ensuring compliance with both global and German standards.
This is the official source for all DIN standards.
Without this standard, every engineer would guess the width and depth of that relief groove. With DIN 76-1, you get specific formulas (usually based on pitch size) for Form A, Form B, and Form F undercuts. din 76-a pdf
The transitional area where the thread depth gradually decreases to zero as the cutting tool pulls away.
DIN 76 specifies dimensions for thread run-outs and thread undercuts, primarily for fasteners (bolts, screws) that utilize ISO metric threads (DIN 13-1).
Short undercut for external threads (used when space is limited).
) specified in the standard must be maintained. If the grooving tool wears down, the radius will change, potentially creating a sharp corner prone to stress cracking. In some modern contexts, ISO standards are superseding
The standard categorizes undercuts into four primary forms based on whether they are for external or internal use and their required length: Application Description External Threads The normal (standard) case for shafts and bolts. Form B External Threads
If you require the official, unedited engineering document for your compliance records, you can obtain it through official standardization bodies. Where to Download Official Copies
However, because these dimensions are universal across European manufacturing, many machinery handbooks, CAD software documentation libraries (like SolidWorks or Autodesk Inventor), and precision component manufacturers offer free, downloadable and data sheets.
DIN 76-A refers to a specific standard for a type of thread, known as a "thread run-out" or "thread end." The standard outlines the dimensions, tolerances, and requirements for thread run-outs on threaded parts, ensuring interchangeability and compatibility across different components and systems. Without this standard, every engineer would guess the
) of the thread. The standard specifies four critical parameters:
DIN 76 is the German industrial standard governing thread run-outs (also known as thread run-outs or undercuts) for ISO metric threads. is specifically designed for external threads, ensuring that the thread terminates properly and a mating part can seat firmly.
, subtract the value in the table from the nominal major diameter of your thread ( ). For example, for an M10 coarse thread ( Technical Drawing Callouts
(Undercut Width): The total width of the groove, including the transition angles.
