Screw modifier problem Im having trouble using the screw modifier to create a screw cap on a lightbulb.  Ive been trying to follow this guys video for it but cant seem to get the screw modifier to do something even vaguely similar to his.  It about 45 seconds in:

https://www.youtube.com/watch?v=P60Fk5YiTds

I created the same sort of edge loop but when I add the modifier it loops in on itself weirdly.  Any help with this? 

Tutorial version edge loop



Tutorial version screw modifier



My edge loop



My screw modifier..
The object origin should be in the middle, not on the thread. Because the object origin is what the modifier uses as a reference for rotation.

If you look at the first screenshot, you can see how the object's origin is at the center line of the bulb, surrounded by the translation widget. Only the edges are left.

In object mode with only the object selected, set the cursor to the object using SHIFTS "Cursor to Selection". That will make sure the cursor is on the same plane as the object. Then place the cursor on the symmetry line of the bulb and use "Set Origin" >> Origin to 3D Cursor from the tools panel on the left.

You might need to adjust the axis that the modifier uses in its settings.