FWIW - Page #145 of Poyer's book, "The American
Krag Rifle and Carbine", has a drawing of the left-side of the Krag Extractor, that attempts to show the recess where the Extractor-Spring is located.
IMHO - There are some 'sub-assemblies' on U.S. Krag models, that were not intended to be taken fully apart, except for repair. These 'sub-assemblies' can be cleaned and lubricated as a unit.
Examples would be: the safety-lever, the magazine cut-off lever, the Striker-rod & Knob, and the bolt-sleeve/extractor/extractor-spring assembly.
These sub-assemblies have some small parts, (springs, rivets, and shaped pieces), that are staked or crimped into place. Taking them apart causes needless wear.
The Krag Extractor is kind of a marvelous flame-blued "wonder spring", with an extractor 'claw' hanging on its end.
It serves as an extractor, a bolt-guide, a bolt hold-open spring, and a bolt 'release'.
Through good metallurgy and heat-treat, it is a surprisingly strong part.
The Krag extractor (which is a tempered spring) is assisted by a subtly positioned second spring (the extractor-spring).
As the Krag Bolt moves forward and nears the point of rotation, the beveled front edge of the extractor-spring slides under a 'shelf' milled into the left receiver wall and adds further tension to the extractor-claw's engagement with the cartridge rim.
Attachment 115861Attachment 115862Attachment 115863Attachment 115864Attachment 115865