Note: All values are in millimeters (mm).
| Standard | Name | Key Difference | | :--- | :--- | :--- | | | Undercuts for metric threads (long version) | Standard undercut for general engineering. | | DIN 76-1 | Undercuts for metric threads | Almost identical to ISO 4755 (Germany uses DIN 76-1). In practice, they are interchangeable for most sizes. | | DIN 78 | Undercuts for bolts with reduced shank | Different geometry; used specifically for shoulder bolts. | | ISO 3506 | Mechanical properties for stainless steel | Refers back to ISO 4755 for undercut dimensions, but property classes (A2-70, A4-80) have different fatigue limits. | tabella gola uni iso 4755
In the world of mechanical fastening and threaded connections, precision is not just a metric; it is a safety requirement. When dealing with hexagon head bolts and screws, one of the most overlooked yet critical geometric features is the gola (often translated as the "undercut" or "fillet groove"). Note: All values are in millimeters (mm)