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Blade broke, don't know why


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I'm fairly new to blacksmithing and I don't know where I went wrong, but today I broke my blade. I was flattening the handle of a drop forged wrench, and I put it in the forge. It's bituminous coal and I use a hair dryer attached to a pipe as an air source. It gets the metal orange-white hot. I took it out after 5-6 minutes and I noticed a chip out of the blade, it was the spine so I dismissed it. But as I started pounding, a crack appeared that ran next to the chip from the spine to the side that the edge was going to be on. I don't know where I went wrong, but I have a few therioes. The first is that, since I didn't brush the blade each time before I pounded, that I pushed some of those chips that fly off into the blade. Another theory is that I left it in the forge for too long and it got too soft. A third is that, instead of just pounding it into a blade shape and then trying to get it longer, I should've pounded it into a long, rectangular shape, like a piece of barstock looks, then formed the blade shape. Sorry for such a long post, I am just angry that I broke my blade and I dont know why it happened, and I don't want to do it again. Any help would be appreciated, Thanks!

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Seeing as you are forging a (drop forged wrench) you have a piece of unknown tool steel most tool steel alloys have spacific tempature ranges they need to be forged at or they may crack, suffer from excess grain growth ...... wothout knowing the alloy involved it is hard to say if you worked it too hot or too cold. 

Hammering scale into the surface makes it ugly but dosent usally lead to cracking( but it could in theroy)

if you are a beginner and you really want to make a knife i would suggest working with a source of known toolsteel. 10xx sieries is more forgiving than most as is 5160 small bars of both can be found realatively cheap.


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Good Morning Leo,

Welcome to the game. This is called the Learning Curve. The School of Hard Knocks.

There are many things that will make material break, quite often you are getting to too hot and then continuing to hit it when it is too cold.

Please add your location to your Avatar.


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My advice to newcomers to the craft is start at the basics. Learn the blacksmithing basics with mild steel before learning to work high carbon steels before learning to evaluate found unknown steels, before making blades from interesting things like wrenches. 

These are different skills sets:

Basic blacksmithing is learning to control the movement of steel to your will. Cathedrals are dressed in wrought iron of spectacular scope and design but if you look closely it's almost ALL BASIC techniques joined together by basic joinery. You just need to know what you're looking at, it's the same as learning to read.

The higher the carbon content the more factors you have to learn to be successful but once you've developed proficiency at the anvil it's an easy step of learning to read the steel's reaction to what you did. Heat, timing, necessary force, when to stop, etc. Once you know how to forge things like leaves, blades of grass, etc. forging blades is easy and you didn't have to toss a bunch of expensive steel in the scrap bucket to learn it. Hmmmm? 

Salvaged or repurposed steel is a different matter, just because someone made up a chart of what valve springs, axles, Bobrat wrenches are made from doesn't mean they got it right or the stuff is made from the same alloys now and you never know how old a thing is. The skills sets you need to learn now are first: eyeball evaluation, you can tell a lot by what it was used for. A coffee can full of dental picks will be pretty tough, they have to take a lot of bending forces and still maintain a point. Or say a pitchfork or hay rake? Those have to be tough and springy. How about pry bars? Drill bits? Jack hammer bits? Tie rods from a pickup truck? 

For our purposes it doesn't really make so much difference exactly what the alloy in scrounged stock is within wide boundaries, stainless is way different and not generally very suitable at our games. We really care about and need to know how does it do what we need it to and how do we need to treat it to get what we need? Can't do that buy asking 45,000 people in 150 countries around the world. You have to learn how to test it in YOUR conditions and evaluate the results. It's not as complicated as it sounds but you need to learn to read things as they happen.

What I'm saying . . . AGAIN is trying to learn how to forge blades as an introduction to this really involved craft is setting yourself up to climb what 4-5 different but related learning curves without knowing enough to know why a thing didn't work. You can't learn from your mistakes if you don't know what the mistake was, just that it failed. Your current question is a perfect example of that. I'm not picking on you when I say NONE of your theories are in the ball park. AND your procedures were almost guaranteed to fail.

Look, we want you to get this stuff right, it's why many of us are here we get together and solve each other's problems and present our ideas for folk to use. I'm not a bladesmith though I HAVE forged and finished a couple in the 50 + years I've dabbled at this craft. However I've achieved enough of a mastery I CAN evaluate found stock and probably maybe make a working blade. Probably maybe? Yeah, nothing is for sure.

My real time advice for now is buy a 20' stick of hot rolled steel, I like 3/8" square but 1/2" round is about the same amount of steel per inch and is a good start. A full stick will help ensure you get consistent steel, modern "mild" isn't as consistent as it used to be, you have to special order 1018 mild but don't bother. Anyway, a single stick is from ONE run of the mill so the scrap it's made from is mostly all the same stuff for the whole length. Rebar is the worst, the alloy can change in inches, you might find anything from old Desoto hoods to drill bits in the same piece. It takes good evaluation skills to make much from rebar.

I like teaching with this weight stock because 3/8" rd or 1/2" sq. is light enough a beginner can finish a project in a reasonable length of time. It's heavy enough to hold heat long enough a beginner has a chance to learn a little from every heat. Heavy enough mistakes aren't permanent as quickly so the student can learn to correct them before they're beyond correction. Make sense?

Then there are hammers, ANY smooth faced hammer is suitable for blacksmithing though it might need a little loving from a file or belt grinder. This is mostly to break sharp edges so they don't leave sharp marks in the work. Doming the face slightly is also a GOOD thing too. My recommendation for a first smithing hammer is my all time favorite the 2 lb. "Drill Hammer." 2 lbs is heavy enough to do serious work without being so heavy it makes your mistakes permanent before you realize you're making one and can correct, it's light enough it won't tire you as quickly, another important skill set is learning to recognize your own fatigue and take a break or knock off for the session. Smithing when tired can not only cause mistakes it can injure you and make you prone to accidents. The Drill Hammer also has a shorter handle so it's more accurate.

It's important to learn good hammer control before you go for power, Power is harder to control as it increases, think Honda Civic as opposed to a 700 Hp. Trans Am. Make sense? Anyway, hammer control is what this craft is ALL ABOUT, it doesn't matter if you get the temperature just right or have the perfect alloy for the project, if you can't hit the target with the hammer you might as well take up a different craft.

Make sense? I hope.;)

Frosty The Lucky.

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  • 2 weeks later...

Overheating leaves the metal  brittle, (what's left of it).   Basically this question reads as "I keep crashing when I race my car, I started drive 2 weeks ago what is wrong?"

Stated this way you can see where all the "learn to forge before learning to forge knives" come from.  I sometimes allow a student to forge a blade early but if I like them it's 1 on 1 as I monitor temps, hammer blows, alloys, etc.  

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Welcome to the forum.

The advice I always give to new people on IFI is to read this thread.


On 9/15/2018 at 7:48 PM, weissleo28 said:

I'm fairly new to blacksmithing

We all started as new and had to learn to walk before running, keep at it and don't get discouraged with failures (I have plenty after 30 years).

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