This document defines the head geometry and wrenching interface for -type fasteners (e.g., bolts, screws, or specialized threaded components) manufactured in accordance with UNI ISO 4755 . ISO 4755 specifies the width across flats and head height relationships for hexagon products, ensuring tool compatibility and torque transfer.
A specific radius is defined for the corner of the groove to avoid sharp edges that act as stress raisers. Comparison with Related Standards
ISO 4755 applies to external threads of fasteners conforming to ISO 261 (ISO general purpose metric screw threads). The standard specifies the dimensions of the (the section where the thread terminates before the shank or head). gola uni iso 4755
| Property | Requirement | |----------|-------------| | Width across flats (s) | Tolerance: h11 to h14 depending on product grade | | Head height (k) | Tolerance: h14 for formed heads | | Wrenching interface | Hexagon external (or internal if specified) | | Reference edge | Underhead fillet or Gola shoulder radius ≤ 0.5× s |
ISO 4755 does not define underhead collar (gola) dimensions. Always reference a supplementary product standard or engineering drawing for complete Gola geometry. This document defines the head geometry and wrenching
This report outlines the technical specifications defined by (adopted in Italy as UNI ISO 4755 ) concerning the shape and dimensions of thread run-outs (grooves) for fasteners such as bolts, screws, and studs. The standard ensures compatibility between fasteners and nuts, preventing stress concentration and assembly failures.
While UNI ISO 4755 focuses exclusively on , it is often used alongside other standards: Comparison with Related Standards ISO 4755 applies to
During manufacturing, the undercut provides necessary space for the cutting tool to exit the thread without damaging the component. Key Specifications and Dimensions
If "Gola Uni ISO 4755" referred to a specific company name (e.g., a supplier named "Gola"), a product line, or a specific internal document code different from the standard described above, please provide additional context. However, based on standard engineering nomenclature, the report above addresses the most likely technical subject matter.
Properly dimensioned undercuts ensure a smooth transition in the threading, which helps prevent stress concentrations that could lead to cracks or mechanical failure under load.
The UNI ISO 4755 standard is the Italian adoption of the international standard, which remains the current and active reference for these dimensions. Purpose and Technical Function