MBTcustom
10-04-2012, 05:03 PM
I have found it necessary to make custom springs on occasion.
Sometimes the only thing standing in the way of good function is adding or subtracting a few pounds from a spring.
The concept of a spring is a simple one. For the most part, what determines the strength of a spring is the gauge of the wire, the coil diameter and the length. The number of coils seem to have little effect on the power that is transferred to the application in comparison with these other variables.
This is just a rough explanation of how I make springs. Please understand that I am not a metallurgist, nor a mathematician. I am a gunsmith/machinist/blacksmith so what you see is what you get, and it is based completely on my experience.
The basic principle of heat treating carbon steel is that you heat it to a cherry red and quench it in oil, producing a very hard, brittle metal.
The next step is to draw the steel back to produce more toughness and less brittleness/wear resistance. This is accomplished by heating the steel to a lesser degree and holding it there for a certain period of time. The draw range for carbon steel is somewhere between 300 degrees (this gives a brittle knife quality result) to 800 degrees (This gives a slightly hard, very tough result that will easily take a set when bent, but can be bent quite far while still giving good resistant force compared to fully annealed steel.)
For spring steel, we want something in between these two extremes.
I have developed a process that gives good results most of the time (ie it hasn't failed me yet) and is easily accomplished without the aid of a heat treat oven.
I have coils of spring material of all different sizes to make custom springs out of, but in a pinch, I have been known to straiten a existing spring of the right gauge wire to get a starting point, by vicing one end of the spring and grabbing the other with pliers, and using a propane torch to straiten it out while it is being annealed.
For short springs, (less than 2.5" long) I wrap the wire around a mandrel while using the torch to help it take form. When I have formed the coils, I hold the spring with needle nosed pliers and use a torch to bring the whole thing to a cherry red glow, then quickly plunge the spring into a jar of oil.
If you need to make a longer spring, you need to make a crucible to help you get even heat over the whole length of the spring. To do this, use your lathe to drill a hole in a piece of round, steel, bar that is a little longer than the spring and only slightly bigger than your spring's OD.
Drill a 1/16 hole near one end of this "tube". Slip the spring into the crucible and then use a finish nail to keep it from falling out.
Hold the crucible with vice grips very near the top of the crucible.
Use your torch to bring the whole crucible up to a cherry red, hold it over the jar of oil and quickly pull out the nail, allowing the spring to fall into the oil.
Now, you need to bring the spring up to a temperature of about 600 degrees and hold it there for about an hour.
Use your lead pot to do this![smilie=l:
Clean the oil from the springs very carefully as this will act like flux and make the lead stick to your springs like glue.
Slip the springs into your pot and leave them for an hour at least.
Take 'em out and enjoy the fruits of your labor.
So far, it works every time, and I take great pride in that I came up with another use for a lead pot in this trade![smilie=l:
Sometimes the only thing standing in the way of good function is adding or subtracting a few pounds from a spring.
The concept of a spring is a simple one. For the most part, what determines the strength of a spring is the gauge of the wire, the coil diameter and the length. The number of coils seem to have little effect on the power that is transferred to the application in comparison with these other variables.
This is just a rough explanation of how I make springs. Please understand that I am not a metallurgist, nor a mathematician. I am a gunsmith/machinist/blacksmith so what you see is what you get, and it is based completely on my experience.
The basic principle of heat treating carbon steel is that you heat it to a cherry red and quench it in oil, producing a very hard, brittle metal.
The next step is to draw the steel back to produce more toughness and less brittleness/wear resistance. This is accomplished by heating the steel to a lesser degree and holding it there for a certain period of time. The draw range for carbon steel is somewhere between 300 degrees (this gives a brittle knife quality result) to 800 degrees (This gives a slightly hard, very tough result that will easily take a set when bent, but can be bent quite far while still giving good resistant force compared to fully annealed steel.)
For spring steel, we want something in between these two extremes.
I have developed a process that gives good results most of the time (ie it hasn't failed me yet) and is easily accomplished without the aid of a heat treat oven.
I have coils of spring material of all different sizes to make custom springs out of, but in a pinch, I have been known to straiten a existing spring of the right gauge wire to get a starting point, by vicing one end of the spring and grabbing the other with pliers, and using a propane torch to straiten it out while it is being annealed.
For short springs, (less than 2.5" long) I wrap the wire around a mandrel while using the torch to help it take form. When I have formed the coils, I hold the spring with needle nosed pliers and use a torch to bring the whole thing to a cherry red glow, then quickly plunge the spring into a jar of oil.
If you need to make a longer spring, you need to make a crucible to help you get even heat over the whole length of the spring. To do this, use your lathe to drill a hole in a piece of round, steel, bar that is a little longer than the spring and only slightly bigger than your spring's OD.
Drill a 1/16 hole near one end of this "tube". Slip the spring into the crucible and then use a finish nail to keep it from falling out.
Hold the crucible with vice grips very near the top of the crucible.
Use your torch to bring the whole crucible up to a cherry red, hold it over the jar of oil and quickly pull out the nail, allowing the spring to fall into the oil.
Now, you need to bring the spring up to a temperature of about 600 degrees and hold it there for about an hour.
Use your lead pot to do this![smilie=l:
Clean the oil from the springs very carefully as this will act like flux and make the lead stick to your springs like glue.
Slip the springs into your pot and leave them for an hour at least.
Take 'em out and enjoy the fruits of your labor.
So far, it works every time, and I take great pride in that I came up with another use for a lead pot in this trade![smilie=l: