If I’ve learned one thing after three decades of forging, it’s that not all steel is created equal. Like many of you, I was once tempted to grab any steel I could find, hammer it into shape, and hope for the best.
I genuinely believed that every old spring held the promise of a perfect blade. But through trial, error, and more than a few broken knives, I discovered the truth. Some spring steel simply isn’t suitable for knife making.
Today, I want to share what I’ve learned to help you avoid those same mistakes.
Let’s explore whether spring steel is good for knife making, how to determine its quality, and how to spot trouble before you start. Part of what makes this craft so rewarding is the knowledge you gain from the process.
What Makes Spring Steel a Tempting Choice?
Spring steel is designed for strength and flexibility. Built to endure flexing without losing its shape, it’s tough, elastic, and often rich in carbon, all excellent qualities for knife steel. Plus, it’s practical for those of us who enjoy salvaging materials.
You can find it in leaf springs, coil springs, and even garage door springs, often for free or at a bargain price.
However, not all spring steel is the same. While some types are ideal for blades, others won’t perform well. Your goal is to identify the right material to avoid wasting effort.
How to Spot Good Spring Steel for Knives
When you come across old springs, you need to evaluate their potential. High-carbon or alloy spring steel can produce durable, sharp, and reliable knives if you know what to look for.
1. Quality Alloy Composition
Car leaf springs and coil springs are among the best finds for knife projects. Many of them are made with 5160 or 9260 alloy steel, which is robust and capable of holding a sharp edge. Garage door springs, which are often 1095 high-carbon steel, are also excellent for knife making.
If you know the source of your spring steel, you’re off to a great start. Steels like 5160 are favorites among bladesmiths due to their durability and edge retention.
2. Bright Sparks During the Test
One way to evaluate spring steel is by conducting a spark test. When grinding steel, observe the sparks it produces. High-carbon steel creates bright, fine sparks that branch out in patterns like fireworks. If the sparks are dull or sparse, the steel may not have enough carbon to make a reliable knife.
3. No Visible Cracks or Fractures
Springs work hard in their lifetime, flexing under heavy loads, which can lead to stress fractures. Look closely for surface cracks, and clean the steel thoroughly before inspecting it. Rust can hide flaws that can cause issues during forging or later on.
4. Successful Hardening Test
Heat a small piece of steel until it’s non-magnetic, then quench it. Once cooled, try to break it with a hammer or vice. A clean, crystalline break shows that the steel can harden, a critical quality for knife making. If the piece bends or refuses to snap, it might not be the right material for blades.
Signs That Spring Steel Might Not Be Knife-Worthy
Not every piece of steel is worth transforming into a blade. Here are common signs that spring steel may not be suitable for knife making:
1. Galvanized Coating
Some springs, like those from trampolines or beds, are coated with zinc to prevent rust. This might sound like a bonus, but zinc produces toxic fumes when heated. It’s a serious health risk, making these materials unsafe for forging.
2. Thin or Brittle Stock
Thin or small coil springs may lack the bulk needed for forging knives. Additionally, springs that are too brittle will likely crack under the heat and pressure of forging.
3. Unknown Composition
Mystery steel is unpredictable. If you can’t identify the type of steel or where it came from, you’re taking a risk. Testing helps, but even then, the results may not be reliable enough for a functional blade.
4. Signs of Severe Wear or Damage
Deep rust, pitted surfaces, and significant cracks are all red flags. These flaws weaken the steel, making it unsuitable for knife making. No amount of cleaning or repair can save steel in poor condition.
Creative Ways to Use Unusable Steel
If you determine that your spring steel isn’t right for knives, you don’t have to toss it aside. Springs that fail the knife test can often be repurposed. They’re great for punches, chisels, or even decorative garden stakes. Remember, every piece of scrap metal has potential when you think creatively.
A Final Word from the Forge
There’s no shame in starting small or making mistakes along the way. Every failure is a learning experience. Testing, experimenting, and studying how materials behave are all fundamental parts of the forging process.
With time, you’ll sharpen your skills and develop an instinct for identifying good materials.
Spring steel is an affordable and versatile resource for bladesmithing, but it demands extra care and knowledge. Clean it, inspect it carefully, and test it before committing to a project.
Whether you’re working with an old car spring or something salvaged from a scrapyard, every piece of steel holds a unique story. You just have to unlock its potential.