The table didn't just provide numbers; it provided the geometry of relief. It dictated the exact width and depth of the groove—the gola —that must be carved into the metal where the thread ended. This tiny, vanished ring of steel was what allowed the nut to sit perfectly flush and, more importantly, ensured the shaft wouldn't snap under pressure.
Note: $l_p$ (Point Length) is often roughly 2 to 3 times the pitch of the thread. tabella gola uni iso 4755
The standard typically recommends a minimum transition angle of 30∘30 raised to the composed with power Sample Dimension Data Thread Pitch ( Undercut Diameter ( Data extracted from standard UNI ISO 4755 tables . Best Practices for Designers The table didn't just provide numbers; it provided
The so-called “tabella gola” (Italian for “undercut table”) is the core part of this standard. It provides standardized dimensions for the groove (undercut) machined at the end of a threaded portion to allow a threaded part to screw fully against a shoulder or to facilitate thread cutting tool run-out. Note: $l_p$ (Point Length) is often roughly 2
In mechanical turning, it is impossible for a cutting tool to create a perfect thread right up to a vertical shoulder without a relief zone. The undercut provides: Tool Clearance: