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 variables typically defined in the standard are:
(often referred to as DIN 76-A based on its primary "Type A" undercut designation) is a German technical standard that defines the dimensions for thread run-outs and thread undercuts on fasteners like bolts, screws, and internal tapped holes. din 76-a pdf
Standard thread undercut for internal (female) threads.
: A sharp 90-degree corner creates a massive stress riser, leading to fatigue failure. The radius defined in DIN 76-A smooths out the transition, distributing mechanical stress. A corrigendum (a minor correction) was issued shortly
: Used for external threads (bolts, studs, and shafts) with standard undercut depths.
While the exact PDF data contains toleranced charts, the standard dimensions generally scale as follows for Form A: Approximately The variables typically defined in the standard are:
"Thread: M12 – 6H – DIN 13. Undercut per DIN 76-A – Form F"
Because DIN standards are copyrighted intellectual property, downloading a complete, official PDF for free from unauthorized websites often exposes you to outdated revisions or security risks.
The DIN 76-A standard has a wide range of applications across various industries, including:
A standard drawing callout for this specific feature is written as: Thread Undercut DIN 76 – AThread Undercut DIN 76 – A