The critical dimension defined in the table is the Chamfer Angle ($\alpha$) and the Minimum Chamfer Flat ($u$).
| Thread Diameter (d) | Chamfer Angle ($\alpha$) | Min. Chamfer Flat ($u$) | Notes | | :--- | :--- | :--- | :--- | | Standard Thread | $45^\circ$ | Approx. $0.2 \times \textPitch$ | Usually roughly 1-2 pitches long. | | Short Thread | Varies | Shorter | For specific short screws. | | ** Rolled Threads** | $45^\circ$ | Defined by run-out | Often naturally formed by the rolling process. |
Visual Interpretation:
UNI ISO 4755 is the Italian adoption of the international standard ISO 4755:1983 – Fasteners – Bolts, screws and studs – Undercuts for metric threads. It replaces older national standards (e.g., UNI 4749) and aligns with modern ISO thread systems (e.g., ISO 68-1, ISO 261, ISO 965).
The standard specifies:
The UNI ISO 4755 standard is part of a broader series of international standards developed to ensure quality, safety, and efficiency in various industrial and technical domains. The "UNI" prefix denotes that the standard is adopted and recognized within the Italian standardization system, while "ISO" indicates its alignment with international standards set by the International Organization for Standardization.
The undercut serves three primary functions: tabella gola uni iso 4755
While the specific details of the UNI ISO 4755 standard can be extensive, several key components are noteworthy: