Help with broken blade

K

Kevin Kf knives

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Jul 2, 2018
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My first broken blade got me today. Its AEB-L, not sure if I should say where I hot it, but I will if it's ok, had it heat treated by one of the recommended places. So I don't grind at all before heat treat, someone told me it's easier to prevent warps. So I grind to where I like it, to 220 on my grinder, then start hand sanding this morning. As I'm getting ready to move on to my next grit, I see a weird round line showing up, about a 1/4 in in diameter. So I try to sand that out and it's getting worse and is now turning into a squiggly line. The question is, steel or heat treat issue?



 
That is a crack in the blade. The HTer should have seen it. It could be from the steel, or a failed HT. If the HTer was a standard blade person/company, then I suspect it was just one of those things that happen. No one gets 100% perfect results with blades. Bring it to the HTers attention and call/email the seller of the steel. The seller will most likely replace the steel. The HTer may offer to do the new blade.

Once all that is worked out, you can try to grind down the spine in a big semi-circle to remove the whole crack. Re-shape things so it is a thumb rest area and make a knife out of it. Grind somewhat gently with a 80 grit belt and a 2" or 1" wheel. Dunk in water every five or ten seconds.

When life gives you a lemon ... make lemonade. Sometimes lemonade is the sweetest beverage.

If you don't have the equipment of skills to grind it out and reshape the hardened blade, I am sure one of the guys near you would do it for you.
 
That is a big crack and in a semi circle, very strange indeed.

Only on the spine, no cracks on the edge?
 
JTknives said:
I don’t think you went with us but if you did PLEASE contact us. If it was another place and thy won’t work with you then still contact me and I will make it right. JT
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Was not you, but thank you for the offer. I'm not really upset about it, I have ruined more partially finished knives than I'd like to admit. I was just wondering what you guys thought.

The part where the crack developed has rough grain, the part that broke when I flexed it, I couldn't see the grain until I took a picture and zoomed in.

Thanks everyone for taking a look and offering help.
 
So I’m going to wager a bet that you had it heat treated by Peters and thy straightened it with a torch in that area. Do you have any way of testing hardness in that area compared to another area. I would be interested in seeing what the hardness numbers are. If you don’t have a way to test it then you could send it to me and I can test it and also get the grain under the microscope and give it a good look and take a few pictures.
 
You are correct sir. I do not have any way to accurately test it. Just those Chinese files. I actually tapped it up an trashed it. Thank you for the offer though. I don't normally use Peter's and was wondering if I should continue using them.
 
That crack formed right on the boundary between the soften steel and the harden steel. The steel is no longer homogeneous and there is stress in the steel at the boundary of those soft spots.

Some people are to blase' faire when it comes to taking a torch to soften a hardened stainless steel blade
 
Good thing that crack showed up when it did. It obviously was not there when you got it back.
The stresses between the soft spot where torched and the surrounding harden steel finally reached a critical point and snapped.

It would have been horrible if the knife was completed in the hands of the new owner and it cracked while being used.

The reality is this can happen to any hardened stainless blade that has had the spine torched
 
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They do use a torch to straighten stainless steel hardened blades.

When that is done you will have soft spots in your blade next to very hard areas and the blade is bent, to straighten it, that stress built into the blade really is not what is wanted in a custom knife.
 
Any news from the Heat treater on the cracked blade?
 
AVigil said:
Any news from the Heat treater on the cracked blade?
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Haven't contacted them yet. I just got the 250 coconut invoice Friday though, made me feel not so cool inside. Plan is to grind on a couple of the other knives I got from them tomorrow. I'll let you know how they look.
 
20191114_060506_zpstyptiwuq.jpg


From the same batch. Not sure why everyone recommends them.
 
JTknives said:
So I’m going to wager a bet that you had it heat treated by Peters and thy straightened it with a torch in that area. Do you have any way of testing hardness in that area compared to another area. I would be interested in seeing what the hardness numbers are. If you don’t have a way to test it then you could send it to me and I can test it and also get the grain under the microscope and give it a good look and take a few pictures.
Click to expand...

Glad I sent you my blade (with another massive batch coming soon). Order #120 should be hitting your step Sat / Mon
 
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