I would like to make some custom made extension springs out of music wire. Can anyone provide the formula's to determine the wire thickness, coil diameter and coil length to achieve a desired spring constant? The motivation is that I need some small springs in my research and it is difficult to find existing springs that match what I need. I've been told that it is relatively easy to wind your own springs with music wire. I'm sure I could derive the formula's, or just experiment, but this will take time. If some ready made formulas and material properties for music wire are available, I wouldn't mind saving some time. Thank you in advance!