A very informative article is presented on the site “the Naked Watchmaker”. An article in English which merits its publicity:
Mainsprings, their function and how they are made.
Isochronism is the primary goal of every modern timekeeper. It is the characteristic of generating a constant, uniform period of vibration, to be able to assure a consistent rate of time. Although every part of a movement is important to achieve this, much of what can be made following the mainspring and barrel would be rendered ineffective if the mainspring is not well made.
Every mechanical watch requires a power source to drive the wheels that lead to the regulatory organ, which is in 99.9% of watch movements an oscillating balance wheel. The power source is a mainspring, wound either manually by hand through a winding crown, or by an automatic winding system incorporated into the watch movement. Although there are always exceptions to every rule in horology, there exist two fundamental types of mainspring…