How do I use OpenSCAD and DSM to cut ISO threads (physical)?

You can quickly generate ISO standard threads using this ready-made OpenSCAD script (right-click and save-as to computer): https://dkprojects.net/openscad-threads/threads.scad 

Make sure to download and setup OpenSCAD first: https://www.openscad.org/downloads.html Try getting the ZIP package which is portable and does not require a full Windows install.

1. Modify the parameter values to your needs and then render the thread inside OpenSCAD. You can simply remove the comment token '//' in one of the examples to allow the compiler to execute it.

The 'metric_thread' module is already defined in the script and the examples cover the various arguments it accepts.

Reference-  ISO metric thread chart with nominal diameter and pitch measurments: 

https://en.wikipedia.org/wiki/ISO_metric_screw_thread

2. Export the render as an STL.

3. You can then import this STL into DSM and use the object as a cutter for geometry you've already created.