EDIT: V2.0 uploaded 20220116 - added radii , larger finger pad, longer body, added ID info
Here's a little 'fixture' for cutting the PTFE tube for Mingda V2 hot ends - It doesn't care how long in mm it needs to be. Just thread the metal tube in flush to the end, and then unscrew it 1/2 turn which equates to 0.5 mm. now stick in a length of PTFE tube and hold tight with cap and trim PTFE tube. This way it does not matter the depth of the metal tube, and will provide you with a PTFE tube approximately 0.5 mm longer than the metal tube. You may need to adjust the amount you unscrew it based on cutting technique. In the end I would say you do not want the PTFE tube more than .5mm past the end of the metal tube. It's definitely not a necessity, but I was looking for a way to get the absolute correct length for the given metal tube.
I have uploaded an stl file , and the native Fusion360 file in case you want to make any changes or to modify the ‘fit’ of the m6 thread - this can be done by changing one of both of the model parameters - ‘P_thread_clearance_ID’ , ‘P_thread_clearance_pitch’
The author marked this model as their own original creation.