what is the lowest number of threads that you can safely have in the track rod end?

Track rod is 12.5mm diameter (steering rack is a cortina item)

thanks

As a general rule of thumb, threads should be engaged the same depth as it's outside diameter, i.e. in your case 12.5mm.

However, this does not apply to all threads. For instance, a Hub Nut.

As a guide, your average bolt should penetrate the female thread by one and a half times its diameter, when used solely in tension.
With rod ends though, you really only want to see about 3 or 4 threads after the lock nut. I do stress locknut, and not ordinary full-height nuts.
If the length of the rod end's thread is only being gripped by its diameter, it will have absolutely no integrity, and will almost certainly cause failure.
The rod end's body is not remotely as strong as a high tensile bolt (even then, you still wouldn't apply possible beam loads to the end of a HT bolt supported by only its own diameter).

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so in my case 12.5mm of track rod inside the track rod end will most likely fail ?

looks like I can get about 8 - 10 turns of the track rod end on to the track rod for correct adjustment. Any good ?

thanks... sorry for being a little dim in the engineering knowledge dept..

thanks,

I think engineering discussions are OK, us lesser mortals may not fully understand the full details. But they do make us aware of issues that we never knew existed (some important some less so).

No offense taken, I was just trying to say that these discussions raise questions and issues that many of us would never have thought of addressing. Even if a differing opinion exists on a subject, had the subject never been discussed we may have been risking our lives by not knowing about it.

At the end of the day there are many grey areas when building a car of this type. The more of these we can sensibly address the better.