Springs
You probably took them for granted before starting a course of study in Gunsmithing. It’s easy to do, they are everywhere and cheap. They rarely fail compared to how much they are operated and are hidden from view. When you stop and think about it springs make a lot of thing possible that would be hard to live without. Before you can make one you have to know what a spring really is made of and how this little moving part works without moving parts.
Springs are made of carbon steel. The carbon has to be of sufficient quantities in the steel before the steel can be transformed into a spring. The best way to make sure of this is to purchase spring steel specifically for spring making. Brownells sells every type of spring making stock a gunsmith is likely to need and I’m sure there are others as well. The old blacksmith didn’t have a way to log on and order spring stock but you can be sure he would have loved to have the resources we have today. The old saying “they don’t make it like they use too” is true about steel and we should be happy. Steel quality was quite a headache for the old craftsman. Still there will be many times a small piece of steel left over from a job can be fashioned into a spring by a gunsmith if he has a basic knowledge that the old blacksmith learned through years at the grinder and anvil.
A quick way to find out if the steel has carbon in sufficient quantities for tempering is to grind a small section on the grinding wheel and observe the sparks. Grinding wheels cut out small cuts of steel so fast that the chips burn. If carbon is present the sparks will be more white than red, shorter than with low carbon steel and have a little flower bloom looking thing on the end. Try it yourself with a piece of cold rolled steel and a piece of spring and look at the difference. You will quickly get a feel for spotting the spring steel.
Ever wonder what the carbon does? Why it has to be heated? Why quenched? Well here is the short version as told to me by an old blacksmith. It might not be a good description for the chemist but it works for making springs and tools. The steel molecules are formed together in a matrix structure and the carbon is outside the matrix. The steel structures can slide past each other without the carbon being in the way. This happens when the steel is annealed or dead soft. When the material is heated to a cherry red heat the steel structures become very active and the matrix opens up enough to allow the carbon compounds to enter the matrix. Once the steel has the carbon dispersed throughout the matrix it is cooled rapidly. This can be a water plunge or other material that would give a little slower cooling than water. This might be quenching oil or even air. This will be important because some steel will form cracks if cooled too quickly. Now at this point in the process the steel is very, very hard. It will stand a lot of compression but no bending and will fracture with the slightest impact. Then the steel is heated a second time but this time the idea is to reverse some of the operation. This is called tempering or drawing. Actually drawing is a good name because your objective is to draw some of the carbon out of the matrix but not all. We want to leave enough so the steel structure will have some grab and resist moving and return to its former position when the pressure is released. This heat will be around 620 degrees F. Depending on the steel makeup. It can be done in a flame, on an electric element, in a heat treat oven or even in a lead pot. The temperature can be judged with color of the steel, oven thermostat, lead thermometer or temperature sensitive material painted on the spring. Quenching is not necessary but a lot of old timers liked to put it in dry lime or cold ashes (it insulates) and after the spring cools it can be tested with several compressions. You will know if you have a spring very quickly. Like I said it isn’t really what happens but it explained the process to me, maybe it will work for you. Or take a course in metallurgy and learn about austenite, pearlite and martensitic formations during heat treatment.
Springs will usually be preloaded (somewhat compressed) when installed in a firearm. Look carefully at the job the spring does before you try to “improve” how it works. Take the 1911 recoil spring for example. With the slide closed the spring is confined to 4 inches, at full recoil it is compressed further to 2 inches. Its job at full recoil is to have absorbed all the recoil, its job at rest is to close the slide and lock the barrel into the slide. If you cut a heavy spring it might still be strong at full recoil (2″) but too weak when the slide closes (4″). I use a simple spring gauge to measure. A flat plate with a .250 hole is held in the vise. A long nail is inserted through the spring and the hole. The nail has a hole in the end that is hooked with a spring gauge and I can see how strong the spring is at 2″ and 4″. It also allows me to sort and tag all those springs that accumulate in the box. I want my 1911 springs to have 6 pounds at 4″ and barely eject with the selected load for a target gun. Duty guns will be allowed to hit the ejector and eject with a snap to insure positive functioning.
Just remember if you cut a spring that you made it shorter but stiffer and more prone to breakage.
The Brownells catalog and most gunsmithing books have directions on making springs. After reading you can see it isn’t really technical, however nothing makes up for knowledge and careful work. So trying making a few practice springs before you make that special spring. Remember that spring will have your reputation on it when the customer pulls the hammer back on opening day!