(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.
: Used for ISO metric threads (coarse and fine pitch) as defined in : The undercut includes a specific radius ( ), a depth ( ), and a width ( ) to ensure structural integrity and proper clearance. Form Comparison din 76-a pdf
: By providing a smooth radius in the undercut, it helps distribute mechanical stress, reducing the risk of fatigue failure at the thread-to-shank transition. Standardization (often referred to as DIN 76-A based on