❌ – Leads to gauge binding and false torque readings. ❌ Using an undercut that is too wide – Reduces the load-bearing thread length and weakens the fastener. ❌ Applying the wrong standard – DIN 76-1 and UNI ISO 4755 values may differ up to 0.5 mm on large threads, causing assembly issues. ✅ Best practice: Always specify the standard on the drawing and, for critical applications, order a dedicated undercut gauge.
The standard specifies the shape and transition between the threaded portion and the undercut, generally requiring a minimum transition angle of 30∘30 raised to the composed with power where applicable. Radii ( tabella gola uni iso 4755
The standard provides a tabulated set of dimensions in millimeters, which are determined by the and the nominal diameter ( ) of the fastener. Undercut Diameter ( ❌ – Leads to gauge binding and false torque readings
While "Tabella Gola" translates to "Groove Table," the reference to specifically points to the international standard for "Fasteners — Product design rules for tapping screws and metal drive screws." ✅ Best practice: Always specify the standard on
The UNI ISO 4755 standard is crucial for several reasons: