The preset process is largely applied on coil spring manufacturing. It is mainly used to guarantee, under work load, that the spring doesn't plastically deform changing the original dimensional restrictions. However, the difficult to predict its behavior under permanent strain is a constraint on projects. All the spring calculations are based on its final geometry (after the preset process), and today the initial geometry definitions are based on empirical information. The aim of this paper, through F.E.M. and experimental work, is to comprehend the stress-strain phenomena involved on the preset process, in order to create a new methodology to design coiling tools.