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new blade for military friend.


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haha yeah steel is strange at times. the crack is about 2 inches down from the tip, near the spine of the blade. and i was thinking about sending the blade out but i don't know who to send it to. and i have only had one other blade crack.

 

IMG_0526.jpg

IMG_0527.jpg

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Think something on the lines like this :

 

http://www.lawranceordnance.com/the_q_store/knives_gerber/lmf_ii.php

 

it is one of the bet field knives designs and can be done with or with out the serrated edges . and will look Awesome when you get it done . add some good handles ,a guard, a pommel and a kydex sheath for attaching it to the LBE Mole gear and you will have a SHTF Knife your Buddy will be proud of and it will save his life if it has too.

 

Sam

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You are using 5160? How are you judging austinizing temperature? What are you using for the quenchant? The reason I ask, I've made many, many blades of 5160 and I've never had one crack, ever. Something's not right here.

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In your earlier pictures (especially the one where it is red hot) it looks like you have a very large cold shut at the tip of the blade. Try cutting the bar off at a 45 degree angle to help form the tip, instead of straight across the bar at 90 degrees. Less metal to move that way and less chance to form a cold shut.

 

~Bruce~

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The spine may have rolled over on itself creating a cold shut, but that will usually crack along the spine.
My money is on deep hammer marks from the heavy forging that were ground flat rather than forged fairly flat before grinding.
Keep in mind, pure stock removal works, forging to shape works, but using stock removal to conceal rough forging does not work very well. It only conceals the internal rippling in the steel. Normalizing cycles will help correct that, but the best way is to go slower with your hammer work and move the steel as evenly as possible.

"New steel from the mill is exactly the way it should be. Our job as bladesmiths is to do whatever we can to not screw it up..."

I forgot who said that to me, but it is most certainly true.
James

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i heat till dull reddish and magnet check. and a mix of peanut oil and motor oil heated up.

 

Remember 5160 is not fully austinitized until it's around 100 degrees F hotter than non-magnetic. This won't make it crack, it just won't harden as much as it could.

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This is a basic misunderstanding that plagues newbies. That misunderstanding that non-magnetic signals phase change. If you can't spot decalesence not the color right where it gets to non-magnetic and then let it get a little brighter. An alternative method would be to get a temperature crayon such as Tempilstik rated at 1500° and wait until it melts then soak it for about a minute trying not to let the steel get much brighter.

 

Doug

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In your earlier pictures (especially the one where it is red hot) it looks like you have a very large cold shut at the tip of the blade.

 

~Bruce~

Looking again I believe you are right, and it is right where the 'crack' is marked in the other photos. I'd be willing to bet that is not a crack, but a cold shut.

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  • 2 weeks later...

so i dont know what im doing wrong.. the new blade cracked even worse.. i heated up more like alan said to do. i watched it. and it cracked. brand new 5160... some one tell me what the hell im doing wrong.

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Do you have any in process pics for the second blade? It is hard to say why something failed without some way to observe the process. :)

 

Are these the first blades you have made from 5160?

James

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yeah james its new 5160. and Alan i am working it yellow to red. it may not be hot enough but ive never had a problem like this.

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Yes, that IS annoying... :huh:

 

Many things can cause cracking, but if this is cracking at the same place as the last one I'd suspect your forging sequence. Last time it was a cold shut from working down a hump at the tip, right? Are you letting the spine spread too wide before flattening it again?

 

Do you have a new metal table in the shop that you're putting the hot blade on to cool? Are you quenching at any point in the process prior to hardening?

 

Something has changed in the way you're doing things or the environment in which you're doing it, and whatever that is is probably causing the cracks.

 

Going back to the first one, look at this picture:

 

IMG_0494.jpg

 

The yellow circles show cold shuts that you managed to grind out later, and the green circle shows where it had those concentric cracks. It looks a little cold in that picture, even though I took the liberty of messing with the tone and contrast to make it show up better.

 

Here's my current working hypothesis on what happened to that one: 5160 can air-harden in thin sections like knife blades. So, you start forging down the tip of the blade, from the correct temperatures, then you start on the bevels. At some point, towards the end of one of the forging cycles you notice a little hump to flatten out on the spine. It's dark red, almost black, but it's still hot so you move it to a cold part of the anvil without noticing and give it a good whack. Meanwhile, the steel has begun to harden as it drops below 1650 degrees F. The TTT curve for 5160 shows it has around 30 seconds to pass the nose of the curve to harden. This is in contrast to 1095, which has about one second to drop past the nose or it will not harden at all. When the blade moved to the cooler spot on the anvil, BOOM! it hardened just enough for that last tap to cause those concentric cracks, or at least enough to set up the stresses that resulted in cracking in the quench.

 

That may not be it at all. It's something to ponder on, though. I haven't done that with 5160 (yet!) but I have with A2. A2 is seriously air-hardening, of course, but it's the same idea. I wanted to get that one last tap to fix a hammer mark, and the end just snapped right off the bar after it cooled a few more seconds. I was holding it up to look at it after that last tap and felt it go. That little "tink" sound you feel through the tongs is a real bummer. :(

 

On either of your blades did you hear or feel anything during the quench?

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thanks for the info alan, to the part about changing the environment of working the metal. no i have not it has been the same.

 

new metal table? no don't have one. i usually let it cool down after forging in a bucket of ashes. which i have done with all of them.

i dont quench the blade till hardening.

 

with the problem of the cold shut i fixed this time. i didn't take pics of the blade in forging state.

 

what i think the problem is that it got to cold and i hit it too hard... which would cause stress that i did not see before hardening.

 

or this probable not the problem but could it be the steel? its new steel from NJ steel baron.

 

thank you for the info and your time. i really appreciate it.

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It's always tempting to get in that one last blow, and it's never a good idea. Been there, done that. ;) That's how I know stuff, I made the mistake already so I can guess how you did it. :lol:

 

And yes, it's very unlikely indeed that it's the steel.

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what i think the problem is that it got to cold and i hit it too hard... which would cause stress that i did not see before hardening.

That's what I like about 1084, you can get away with stuff like that... with a steel that has air hardening tendencies (5160, O1, L6, etc), don't hit it once it starts recalescence, you might get away with it once but it will eventually bite you. Get it too hot and it will do weird stuff too. This is one of the reasons I've phased out 5160 and gone over to mainly 10xx series steels with a bit of w2 thrown in the mix.... That said, I'd be willing to bet there is nothing wrong with the steel, 5160 makes a great knife, I just don't like using it anymore for purely personal reasons.

 

Third time's a charm, the next one will turn out perfect.

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thanks for the info guys.

 

i normalize the blade before hardening. heat it up and let it cool down. is that the right way??

 

and Alan i think your right. that i hit it when it was too cold. and it is very tempting to get one last blow in.

 

and lets hope that the 3rd time will work

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It depends on how hot you're heating it, and if you're letting it cool long enough before heating it again. You only need to heat it to a max of 1600 degrees, then let it cool to black in still air. With 5160 I do this three times after forging, then three times after grinding. I prefer to do this at night, since the steel will glow at a dull orange and it's much easier to gauge the temp. In bright daylight, it will appear almost black. Which makes me wonder, are you quenching the steel in bright daylight? If so, it's possible you're overheating for the quench. Just my .02

Edited by Freya W. Ward
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