Making Springs?

[Maillemaker]

I've been wondering lately: how do blacksmiths make springs? Obviously the steel has to have the correct carbon content, but what is the procedure for "convincing" a piece of steel to spring back to it's original position?

[pkrankow]

Believe it or not it is the same as modern makers make springs. The difference is instead of controlled tempering ovens, you need other ways of managing temperature.

Salt or lead pots, heated plates and allow the colors to run, repeatedly quenching and flashing oil in a muffle (heated pipe in the forge) there are probably many other means of doing it using modern or antique materials, and antique methods.

Phil

[ThomasPowers]

Choose an appropriate alloy, choose an appropriate size/shape, forge to that size/shape, heat treat for that alloy and usage.

All steel has pretty much the same springiness; it's the yield point which differs! Which is why we often use mild steel for replacement post vise springs. We can design it so it doesn't get close to the yield point and so is fine in that use.

[Greenbeast]

Interesting!

[tomhw]

It is very important to have a uniform cross section even on tapered leaf springs. Thin places flex more than thick sections. After forging anneal or normalize and then file or grind the surface to remove hammer marks and insure uniformity.

[forgemaster]

To make a spring it helps to use spring steel, to harden quench in oil from 850 deg C (orange) then you can temper back with a greasy stick. If you want search on here for "greasy stick". We've already done posts on this topic.

Phil

[Maillemaker]

So, then, what is "spring steel"? Is is a specific carbon content? I know that 5160 is used for leaf and coil springs, but it seems like there is more to it than that.

[thingmaker3]

"Spring steel" is any steel good for making springs. 5160 and 4140 are good choices. Pretty much any low alloy steel with 35 to 75 points of carbon will work. Plain carbon steels with 70 to 95 points carbon will work. I've read that the 300 series stainless can work.

It's a higher yield strength you're after in a spring.

[pkrankow]

"Spring" steel can also be made by work hardening mild steel, typically by cold rolling or cold drawing to reduce thickness then cold forming.

This is typically how brass springs are made, but has been used for light duty steel springs.

Phil

[Frank Turley]

In old timey blacksmithery, there were no alloy steels, unless by accident because of the ores involved. I read some time ago that during those times, an attempt was made to use a steel of a carbon content approaching 1%. Less carbon content would work, but not less than 0.65%. In the "Gunsmith of Williamsburg" video, Wallace Gusler quenches the gun springs in oil, then cleans them and makes them scale free (bare metal). He tempers them by placing on a wide, flat bar of iron which is being heated on the forge fire. They are placed on edge, thick side down. When the pale blue tempering color appears, the springs are removed quickly and quenched again to "hold the temper." The pale blue is 590ºF. A little above that, you reach 626º, which is a gray temper color. This gray color is fairly hard to discern, but some springs go to this heat for tempering. It may be a matter of experimentation. The gray color goes by other names, sometimes termed "gray-green," sometimes "ocean green."

Gusler is shown squeezing the little Vee shaped spring to test it. If it is too crisp, he removes metal slowly by filing. He says, "The springs file with reluctance, but you can file them down."

Larger springs were more difficult to temper. I think they used oil and blazed it off. Each coating of oil and blaze-off would raise the temperature a certain amount. I'm guessing the fine carriage springs and wagon springs were done in this manner after hardening.

[jimmy seale]

i read some where, on smaller springs they would wrap the spring with wire (after hardening) dip it in oil and set it on fire. when it burned out it was tempered. the text didn't gave any specifics about temper color, etc. so i just thought i'd throw this in the hat, jimmy