# Calculation of critical internal thread according to VDI 2230 Part 1

I’m doing a “Systematic calculation of highly stressed bolted joints – Joints with cylindrical bolt“ according to VDI 2230 Part 1. In step of calculation R11 “minimum length of engagement”, when my internal thread is critical, I have to calculate the ratio of $$s/d$$.

In my specific application I’m using a tapped thread joint (TTJ) and I’m connecting some kind of tube (internal thread) with a threated bolt. And because my tube is thin-gauged I get a small $$s$$ and therefore my ratio $$s/d$$ is smaller than $$1.4$$.

VDI 2230 only considers ratios greater than $$1.4$$ and here my questions arise:

• What is the effect on my calculation when I’m out of the mentioned ratio-borders?
• Is it possible to compensate the effect?
• What’s the amount of error I’m introducing?
• ...

Okay, I could reconstruct my connection – but that’s not the topic of my question.

Thanks in advance for your help.