This was actually a model that I remixed from another model a while ago but unfortunately can't seem to find the original model. 

 

The change I made to the original was to increase the length of the model -it was ~5 cm before, now it's 8 cm(completely screwed, ~12 cm completely unscrewed)- and added a groove at the bottom so that a magnet can be glued to the bottom and it holds in place so much better.

 

It's printing fine when printed BOTTOM on magnet hole down and SCREW on screw head down.