(Technical/legal remark: this is an article about home metallurgical works. When done properly everything can be perfectly safe. Despite of it I shall not bear any responsibility for direct/indirect damages, skin/property losses etc. you will potentially suffer by application of it. Everything you do you will do on your own.)
When I got a brand new Hotas Cougar some two years ago, it brought to me a completely new dimension of my virtual flying. HC is metal solid, sympatically hard piece of hardware, able to firmly stand on a desktop while you are trying to withstand all furious maneuvers, attacks and counterattacks in usual dogfight. Anyway in calm periods of flying I realized one of few oddities of this device. Original springs in X-Y axes were too hard for me, after while of holding of slow turn I felt quite strong tiredness in muscles of my hand. So I decided to make a new pair of springs. Believe or not, this can be made at home very simply. My father many years ago tought me the fundamentals of the "black craft" so I know how to do it. It's even not difficult if you have the basic knowledges of works with metal materials.
First of all we have to get a proper spring wire. It must be a steel, not an iron. Steel material is able to be hardened by quenching. Quenching is a process of thermal treating of steel, in which the metal will recrystallize and become harder and more brittle. The process consists of heating over eutectoid point of material (about 720 ºC) and rapid cooling down through this point.