| Thread Size (M) | Pitch (P) | Undercut Width (a) | Undercut Diameter (d₂) | | :--- | :--- | :--- | :--- | | M3 | 0.5 | 0.8 mm | 2.2 mm | | M6 | 1.0 | 1.6 mm | 4.6 mm | | M10 | 1.5 | 2.5 mm | 8.0 mm | | M20 | 2.5 | 4.0 mm | 17.0 mm |
Note: These values are indicative. A genuine DIN 76a PDF contains complete tables up to M100 and beyond. A hybrid version also exists in newer revisions of DIN 76a (Form F), which combines a run-out curve with a final undercut groove for maximum stress relief. How to Read a Technical Drawing Using DIN 76a When you see a notation on a blueprint, it typically looks like this: din 76a pdf
G76 P010060 Q100 R50 G76 X... Z... P... Q... F... The "60" in the first block defines a 60-degree included angle for the thread run-out. But for a DIN 76a run-out, you would typically use a 30-degree flank angle. This means you must use specific vector calculations from the standard to set your P values correctly. | Thread Size (M) | Pitch (P) |