Din 76-a: Pdf
(or thread relief) for fasteners with external ISO metric threads. It is a critical engineering standard used to ensure that a threaded component (like a bolt or screw) can be fully seated against a flat surface or "bearing face" without interference from the unthreaded portion of the shank. Core Purpose of DIN 76 Form A
A corrigendum (a minor correction) was issued shortly after the July 2025 version. It corrected a value in Table 1 for pitch P=5.5mm from 3.8mm to 2.8mm for the radius "r". Customers who purchased the previous document received this correction for free, but it's always best to purchase the most current document directly.
The DIN 76-A standard is a small detail that makes a massive difference in the manufacturability and longevity of threaded parts. By adhering to the defined geometry for thread runouts, you ensure that your parts can be machined efficiently and will perform reliably under load. din 76-a pdf
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specifically defines the geometry of a groove machined into a bolt or shaft right where the thread meets the unthreaded shoulder. Why is a Thread Undercut Necessary? (or thread relief) for fasteners with external ISO
If you have a drawing or a requirement citing "DIN 76-a," it is asking for the of the undercut calculated according to the DIN 76 standard.
The is an essential technical document for any engineer or machinist working with ISO metric threads. It is the definitive source for the precise dimensions of thread run-outs and undercuts, offering the critical specifications for both Form A (normal) and Form B (short) designs. It corrected a value in Table 1 for pitch P=5
Below is an indicative reference table mapping common metric thread pitches to their corresponding DIN 76-1 Form A dimensions. (Note: Always verify with an official, licensed DIN 76-1 PDF for manufacturing purposes). Thread Pitch ( Undercut Width ( Transition Radius ( Depth of Undercut ( 0.7 mm 0.8 mm 1.0 mm 1.25 mm 1.5 mm 1.75 mm 2.0 mm