(Radius): The curvature radius at the bottom of the groove to minimize stress concentration. DIN 76 Form A Dimension Chart
When a bolt or threaded shaft is machined, the thread-cutting tool cannot run cleanly directly up to a shoulder or a flat surface. This leaves an incomplete thread section known as a run-out. An undercut (or thread groove) solves this problem by:
: While the 2016 version is common, a 2025 edition of DIN 76-1 is the most recent active standard.
) of the metric thread. Below is a reference chart for common metric thread pitches under the DIN 76-1 Form A specification: Thread Pitch ( Undercut Diameter ( Undercut Width ( Transition 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) Note: " din 76a pdf
Without an undercut, a mating female part (like a nut or a tapped hole) cannot seat flush against the shoulder. solves this problem by removing a small section of the shaft material at the shoulder, allowing the mating part to tighten completely against the flat surface. Form A vs. Other Forms
All dimensions are in millimetres. * Scope. This standard specifies dimensions for thread run-outs and thread undercuts for bolts,
DIN 76A is a German standard for a specific type of thread, commonly used in engineering and manufacturing applications. The standard defines the dimensions and tolerances for a metric thread with a 60-degree angle, similar to the ISO metric thread standard. (Radius): The curvature radius at the bottom of
These are the international equivalents upon which DIN 76-1 is based. The primary reference for metric thread profiles.
" represents the nominal major diameter of the thread (e.g., for M10, Why Use DIN 76A Instead of a Thread Runout?
CNC programmers and manual machinists can utilize standardized tooling and programming cycles, reducing setup times and errors. An undercut (or thread groove) solves this problem
Engineers, machinists, and quality control inspectors frequently search for the to access official blueprints, tables, and formula charts that define Form A (External Long) thread undercuts. This article provides a comprehensive breakdown of the standard, its technical calculations, geometric principles, and how to read its design parameters. 1. What is DIN 76 and Form A?
Because DIN standards are copyrighted, full official copies are rarely free. You can access or purchase the latest version through authorized distributors: Intertek Inform DIN 76-1:2004-06 - Intertek Inform
If you are searching for a or trying to understand how to implement this standard in your CAD models and manufacturing drawings, this comprehensive guide covers the technical specifications, dimensions, and practical applications. What is DIN 76-1 Form A?
