Broken case extractor

[flanker]

Anyone care to explain just how the tool works. I looked at one today and at the small end of the tool it screws into the larger section. Why is it made this way? And just how well do they work?

[jsta5.56shooter]

ok, the extractor is slipped into the chamber as if to load a round,the bolt is pushed onto the extractor head(where the spent shell head used to be) and the bolts extractor locks onto it. as you pull the bolt back again,it pulls the large (knob looking) end into the sleeve and it expands enough to grab the neck of the broken shell and pulls it out of the chamber. but thats just a guess,i have not tried or had a reason to use mine yet.

[flanker]

Bought one just in case but have not needed it yet. I just wonder why the small end is screwed into the larger section. Does it need adjusting?
Thanks for answering my post.:)