Flat spiral springs are generally shaped into a form of Archimedean spiral.
Shaping is done either by winding the spring strip onto an axis or using the so-called coiling process.
The winding process requires precise coordination of the properties of the spring materials, the required spring geometries, the torque properties and the coiling tools used. It has limitations in terms of coil spacing and mounting geometries. The parameters are tested and adjusted to the specific application.
In the coiling process, the radii of curvature of the individual coils are programmable and can therefore be designed individually. In particular for applications that only allow a very small hysteresis, this manufacturing process offers advantages that allow contact between the coils in the working range.
In times past, springs for timepieces got their typical blue tempering color from the iron content in the material and their heat treatment, which did not yet take place in a high vacuum. This tempering color was state of the art at the time. Since use of the more sophisticated material alloy NIVAROX started and the improvement of the heat treatment process, the springs are now basically bright.
In mechanical watches, however, blue springs are extremely popular, because in contrast to the gold balance and watch mechanism, they come across as very elegant. Today, spiral springs for timepieces are given their blue tempering color using a process developed specifically for that purpose.