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The is an essential technical document for any engineer or machinist working with ISO metric threads. It is the definitive source for the precise dimensions of thread run-outs and undercuts, offering the critical specifications for both Form A (normal) and Form B (short) designs.
Disclaimer: This post is for informational purposes only. Always refer to the official, current version of the DIN standard for engineering decisions.
: Maximum width of the undercut including the transition angle.
When engineers write “DIN 76‑A” on a drawing, they are telling the machinist: manufacture an external thread undercut according to DIN 76‑1, Form A, with the standard normal length . The PDF of the standard contains the exact formulas and tabulated values that determine how deep and how long that undercut must be for a given thread pitch.
Implementing DIN 76-A ensures that your components are universally interchangeable, easier to machine, and structurally sound. Whenever a male metric thread must bottom out perfectly against a shoulder, incorporating the Form A undercut is the professional standard. din 76-a pdf
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You cannot find a free legal copy of the full DIN 76-1 PDF on random websites. The standard is copyrighted by and sold through publishers like Beuth Verlag .
is a technical standard from the German Institute for Standardization that specifies dimensions for thread run-outs (where the thread ends on a component) and thread undercuts The is an essential technical document for any
The exact dimensions of a DIN 76-A undercut depend entirely on the nominal diameter ( ) and the of the metric thread.
The dimensions of a DIN 76‑A undercut are . This means that once you know the thread pitch, the undercut dimensions are fixed by the standard. The table below summarizes the key parameters for external threads, as used in CNC controls such as HEIDENHAIN.
The transition area where the thread depth gradually decreases to zero.
Draftspersons and design engineers use the PDF to accurately model components in 3D CAD software (like SolidWorks, Autodesk Inventor, or Creo). Inputting the correct undercut parameters ensures that interference checks in digital assemblies mimic real-world behavior perfectly. 2. CNC Programming (G-Code generation) Machinists programming CNC lathes require the exact width ( ) and radius ( Always refer to the official, current version of
Approximately €80–120 for the PDF (as of 2026).
Because DIN standards are copyrighted intellectual property, complete engineering handbooks containing the official DIN 76-1/DIN 76-A standard PDFs must technically be purchased through authorized distributors such as Beuth Verlag or the ISO Store.
: It allows the mating component (like a nut or a tapped plate) to screw down completely flush against the bolt shoulder.
While you should always consult an official DIN 76-A PDF chart for precise manufacturing tolerances, here are the standard dimensions for common metric thread pitches: Thread Pitch ( Undercut Diameter ( Undercut Width ( Undercut Width ( Corner Radius ( (e.g., M3) 0.7 mm (e.g., M4) 0.8 mm (e.g., M5) 1.0 mm (e.g., M6) 1.25 mm (e.g., M8) 1.5 mm (e.g., M10) 1.75 mm (e.g., M12) 2.0 mm (e.g., M16) 2.5 mm (e.g., M20)
These dimensions (in mm) are standard for common bolt sizes using Form A: Thread Size ( ) Pitch ( ) Undercut Diameter ( ) Length ( ) Radius ( ) M10 M12 M16 4. Where to Find the Official PDF
Form A undercuts provide a "run-out" zone at the end of a thread. This allows a mating part (like a nut) to be screwed flush against a bearing face and provides clearance for the threading tool (lathe tool or die). Feature Form A (Normal/Long) External ISO Metric Threads (DIN 13-1) Depth ( ) Approx. (Pitch) Length ( ) Approx. Transition Radius ( ) Approx. Angle Usually 30∘30 raised to the composed with power or 45∘45 raised to the composed with power lead-in 3. Sample Dimensions for DIN 76-A (Metric Coarse)