If you just need the value of $a$ (the width) for a standard metric thread, here is a quick reference table derived from the standard:
| Thread Pitch ($P$) | Width of Undercut ($a$) | Radius ($r_1$) | Undercut Diameter ($d_3$) | | :--- | :--- | :--- | :--- | | 1.0 mm | 2.0 mm | 0.5 mm | $d - 1.6$ | | 1.25 mm | 2.5 mm | 0.6 mm | $d - 2.0$ | | 1.5 mm | 3.0 mm | 0.8 mm | $d - 2.4$ | | 1.75 mm | 3.5 mm | 1.0 mm | $d - 2.8$ | | 2.0 mm | 4.0 mm | 1.0 mm | $d - 3.2$ | | 2.5 mm | 5.0 mm | 1.2 mm | $d - 4.0$ | din 76-a pdf
Note: $d$ is the major diameter of the thread. If you just need the value of $a$
This report provides an overview of DIN 76-1:2016-12 (the latest version), which specifies dimensions and types of thread run-outs and thread undercuts for metric ISO threads according to DIN 13-1. The goal is to ensure safe, standardized relief of thread ends in machined parts. If you are looking for the DIN 76-A
When designing mechanical components, engineers often focus heavily on the thread tolerance, pitch, and diameter. However, one critical aspect that is frequently overlooked is the thread runout (or thread undercut). This is where DIN 76-A comes into play.
If you are looking for the DIN 76-A PDF to reference the exact dimensions for your technical drawings, this post breaks down what the standard covers and why it is essential for manufacturing quality.