Hi Barry and Friends
this is my last reflection about
the exact execution of a Globoid Worm Gear ...
1- first of all we must start from the gear wheel we want
be moved
2- we draw the wheel with the Max Plug, asking for output
also the Pitch Circle
3- we extract the profiles of the teeth and reposition them in a manner
fair to the outside, considering them as teeth
of the rotating helical shaft
4- We create an arc of circle that has as referents the centers of the various
sections of the teeth of the shaft
5- We create a Sweept that has the teeth as profiles and as rail
the spiral formed with reference to the circle arc
6- join the section of the Shaft at Swwept

Work completed
at this link :
http://www.mediafire.com/file/4pctkf2pd0rdhxd/Globoid_Worm_Gear.zip/file
the files and some pictures
best
alberto