I'm trying to follow the following answer from the site: How to model the bottle threads?
I could do almost everything, but when I have to do the (spiral) loop cut the program doesn't allow me and I don't know why and in the answer there is no clarification of how it's done.
Additional info: Before I remove the screw (even after doing the knife intersect) I can do the spiral loop ring as the picture shows. When I delete it I cannot do the spiral loop cut nor select the linked objects all the spiral with CTRL+L and I have to do it manually.



