Metric Trapezoidal Thread: TR

[adrianschlatter]

Add TR-thread.

A good starting point (thread specs including tolerances) is here..

[adrianschlatter]

The link above does not work anymore.

[fgoebel]

It is reachable per wayback machine: https://web.archive.org/web/20200311203631/http://mdmetric.com:80/tech/thddat16.htm

I was looking into this, but I do not understand the awk scripts yet.

[adrianschlatter]

Great that you are considering a contribution to threadlib 😀

Yes, this part is a bit awk-ward. Too bad that OpenSCAD is no general purpose programming language. Otherwise I would have written everything as OpenSCAD code.

Where are you stumbling currently? What the awk-scripts are for? Or is it more how to write awk in general? Maybe I should add some documentation on how this works.

[fgoebel]

I have only used awk for some simple tasks from cli, but never written any awk-scripts yet. But understanding the scripts is the easy part I think.

Your documentation is really good actually, but maybe you could make a sketch to explain where Rrot and Dsup are ending up in the final thread/bolt/nut?

As a first thing I added a table for TR Screws yesterday in #55.

I will try to calculate the required values for an example by hand and then use this to write the required awk script.
As far as i understand the threads are designed to be "in the between" the min and max values provided, for examlpe d=(d_min+d_max)/2 ?

[adrianschlatter]

Yes, threadlib aims for symmetric tolerances by aiming at the center of the range given in the norms.

Regarding Rrot and Dsup (=2 * Rsup) I have extended the sketch in Design of Threadlib to show where the support is and what Rrot and Rsup are supposed to be.