This is just a threaded rear cap for M39 lenses.
Here it is fitted on my Jupiter 8 lens
You may adapt the SCAD script just changing a bit this line :
clearenceM39 = 1.0; //add some play between nut and bolt
(If the screw is too tight increase the value (eg: clearenceM39 = 1.5; //add some play between nut and bolt)