Making of Magnifying Love by Paco Morales, Mexico


Modeling screw with thread and nut


For screw create a Helix and weld the vertices, but we need to know the distance between them in order to weld them properly.





In Top and front view, make 2 helix.



Now change the height of the helix, so it can be joined in its end, and we can then adjust the vertices. You can see below.


Make the polygons and adjust them as shown in the below images...



For the lower part of the screw you can use this references.


Here are some links to other techniques to do screws. 

http://www.angelfire.com/linux/juanm/
http://www.caddigest.com/subjects/AutoCAD/tutorials/select/southworth_3d_screw.html