The standard is divided into parts based on the type of thread being used: DIN 76-1: For ISO Metric Threads
Type A to be used where. The dimensions of blind tapped holes with thread run-out shall be as given in figure 4 and table 2. DIN 76-1 - 2016-08 din 76a pdf
) : For Form A, the width is typically around . The standard is divided into parts based on
: For internal threads (Form C and D), the undercut diameter must be larger than the nominal thread diameter. Din 76-1 | PDF | Screw | Metalworking - Scribd : For internal threads (Form C and D),
: The diameter of a Form A undercut is smaller than the thread's minor diameter. Width (
Without a proper undercut according to DIN 76, a nut might not be able to sit flush against the bearing surface of a bolt. The undercut provides a "clearance" zone where the cutting tool exits the workpiece, ensuring: