I got a beautiful 16mm movie lens - a B&H Lumax 25mm f1.9 lens. In order to clean it and relube I removed the screw helicoid WITHOUT marking the alignments.
There is one collar that attaches to the lens body, one collar is the rear C-mount and the focus ring that is on top of these 2 collars.
The rear collar has a screw that goes into a slot in the lens body collar.
However, the threads in the 2 inner collars are different, so when I align the 2 inner collars and screw into the focus ring, the lens body collar moves more than the rear collar and the screw slips out.
I will post pics soon - but I would think simple screw helicoids operate the same way.
So how do you fine folks reassemble screw helicoids ?