The balance spring is actually a compound term.
Functionally speaking, it is divided into two concepts: the balance and the spring.
In the 21st century.
The spring has been optimized to the limit, becoming an extremely fine spiral-shaped spring, 99.9% of which is used in mechanical watches.
It is about 3-4 times thinner than a human hair, with a total weight of about 2mg, yet it can withstand 600g of tension, with considerable toughness.
In timepieces, the inner end of the spring is fixed to the axis of the balance, and the outer end is fixed to the balance bridge.
When the balance is driven, the spring fixed within the balance will uniformly expand and contract due to its elasticity, simultaneously driving the balance to oscillate back and forth.
The driving force on the balance causes the spring to exert pressure, contract, and expand, driving the balance to rotate clockwise or counterclockwise.
