Fractures while forging

Joined
Dec 31, 2006
Messages
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I have been inspired by Wayne Goddard's $50 knife shop. I tired to make my first blade today with mixed success. I cut up a leaf spring from a car and heated it in the forge. The general shaping was going very well, but then I noticed a couple of cracks along the spine. When trying to shape the handle over the horn, a crack opened up that makes the first attempt finito and is sending me back to the drawing board. I also noticed a crack near the tip.

I may be leaving too many unanswered questions, but I'm wondering if I did something wrong that I should avoid on the second go-around. Your thoughts would be appreciated.

Mark.
 
I can't resist being a bit of a smart alec....how does that car ride without the spring?
Sorry, as a "stock-remover", I can't help you but there are alot of skilled hammerers/ anvalizers who ought to be able to give you suggestion.
Just don't get too frustrated....knifemaking is a lifelong learning experience!
 
Well, from the sound of it, you might have been hammering with the steel too cold. Using color as a guide is only REALLY useful if the lighting conditions are known, but I'll set a baseline of "dim surroundings with no direct light on the steel". Think dusk.

You should be forging that steel at a bright orange color. Once it gets down into the red stop hitting it and make it hot again. You should also be able to feel a difference in how the steel moves after a little hammer time. When it starts to fight you, get it hot again. There's no sense in hitting steel that's too cold to move well. You'll just crack the steel and tire your arm out.

If temperature wasn't your problem, the spring may have been cracked before you started. If that's the case, toss it and get another spring.

-d
 
Also keep in mind that of all the used carbon steels out there a vehicle leaf spring has thousands of hours of stresses it has endured. It is very possible that the cracks were allready there but not completely visible. I use leaf spring steel alot but I have a very good supply of new stuff from a local custom spring shop. They charge me the same for the new as the used.

The fact that they are no longer on a car or truck means they were replaced most likely due to fatique. My dad worked for a automotive leaf spring company for 27 years. I would watch him take a set off and in the process they would sometimes crack. The cracks were most likely allready there but the removing process accelerated them (impact wrenches, sledge hammers etc).

If you can get ahold of new leaf spring you will have a much lower potential for cracks then using some very tired, worn and stressed spring steel.

This is a piece of used 1" leaf spring that I cut off and discovered a very large internal crack.
leafspringcrack003-web.jpg
 
Hi Mark

Hammering when the steel is cold is something that comes to mind.

I am assuming the steel is OCS [ old chevy spring ] [5160] being the

common term. Work it when it is in the orange and above color range. Stop,
when the steel quits moving and reheat. The use of a magnet, to familerize

yourself with the tempertures will help you learn about temperatures.

The steel will be at 1350 or so when the magnet does not stick.

Work the steel above this temperature. I work 5160 at 1600 or there

abouts.

Good luck and keep hammering it takes time to learn forging.

Fred
 
after reading your responses, I think it is probably a combination of hammering after it had cooled too much, and using old springs. All of my work before this has been with mild steel, and I do have a habit of hammering after things have cooled to the point that they should have been put back into the forge. I guess I enjoy the shaping so much that I resent the time waiting for the colour to return. Need a shot of patience, I imagine.

I was happy with the shaping, but would have needed to use some stock removal as the hammer blows need some improvement. I'm going to abandon the springs that I have, and may try a coil spring. Will those have the same issues as leaf springs?

Thanks for your help,

Mark.
 
to keep you hammering going put a few pieces to do in at once and then just rotate through them.

the hammer blows (from what i have been reading) to be smothed out, as the metal cools you use the cooled state for smothing

-matt
 
I believe coil springs are 5160 as well. All of my forged knives needed stock removing afterwards since my hammer blows were downright terrible. The more recent ones have been better though.

Good luck!
 
Even "simple" steels without chrome like 1080 and W2 will crack if you whack em when they are cold........Don't EVER try that with O1.....newbie voice of experience here.....lol. You can get new 1 1/2 x 1/4 5160 from a steel supplier for a reasonable price. I paid a few extra bucks and had them cut the 22 ft bar into 3 ft lengths the one time I bought some locally. Mind you it will probably already be at srping temper unlike the stuff you get from specialty suppliers like Admiral.
 
I believe coil springs are 5160 as well. All of my forged knives needed stock removing afterwards since my hammer blows were downright terrible. The more recent ones have been better though.

Good luck!
Hey...like Ed Fowler, Ed Caffrey and J.D. Smith always say....Forge it thick and grind it thin....:D
 
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