CNCSimulator Pro

user guide
Index Threading

For threading layers, no contour is needed. Only the start and end point.
Just as with Rough cutting, you need to add two points to the layer that defines the "operation window". If you are not sure on how to do that, please read about it under roughing.
Thread Depth The total depth of the thread.
Step Depth Depth of each threading pass.
Pitch The pitch of the thread. 
These three are the most important for the simulator. If you want in-depth information on each of these parameters, please google "G76 threading cycle". You will find loads of pages that explains these parameters.
Special note: For the threads to look nice when simulating, we need to boost up the resolution temporarily. You can add the special command $OverrideBufferQualitySetting 8 to the very top of the CNC code to get a better resolution (and slower simulation speed).