Just broke a blade...help...

[sunshadow]

Sunshadow,that's very true .However years of experience [even in Syracuse !] has shown that people think they can understand things better if they touch it ! So the nice clean fracture surface quickly becomes damaged !!

No kidding!
it seems the first thing fencers do with a broken blade is to try to fit it together again, as if by somehow aligning it correctly will create a magic zone of solid-state cold welding that will unite the broken pieces, then of course everyone within 10 miles runs their index finger across the broken stump to see if it broke sharp or not, I would assume so that they can feel some sort of shared danger with the person on the receiving end of the thrust who may have been endangered :jerkit::jerkit::jerkithad it been an overcalibrated thrust, had it broken sharp, had their puncture resistant protective gear failed etc):jerkit::jerkit::jerkit:

Personally besides messing up any possibility of metallurgical failure analysis, I think that they are actually putting themselves in more danger by trying to cut themselves on the same possibly sharp end that the guy next to them just tried to cut himself on, than the guy who just was on the receiving end was in

-Page

 

[Patrickknives]

I would try to bend the part that is left to see how it responds, could provide some info if there were cracks or something in the HT. Too bad

 

[mete]

Terminology - that's not a microcrack at 1/8" long. Microcracks can be as short as the diameter of one grain !! I have a photo of one like that in a book but it's not quality enough to photo. What you have is just a quench crack formed in one of the quenches as I suspected .You get a quench crack and don't notice .Then you HT again and the crack surface forms scale at high temperature .This section has the dark layer and on the final quench the crack extends .The extended part has a clean light color since it hasn't been exposed to high temperature !!

 

[mdoyle]

Terminology - that's not a microcrack at 1/8" long. Microcracks can be as short as the diameter of one grain !! I have a photo of one like that in a book but it's not quality enough to photo. What you have is just a quench crack formed in one of the quenches as I suspected .You get a quench crack and don't notice .Then you HT again and the crack surface forms scale at high temperature .This section has the dark layer and on the final quench the crack extends .The extended part has a clean light color since it hasn't been exposed to high temperature !!

Yeah what he said!

 

[scottickes]

Terminology - that's not a microcrack at 1/8" long. Microcracks can be as short as the diameter of one grain !! I have a photo of one like that in a book but it's not quality enough to photo. What you have is just a quench crack formed in one of the quenches as I suspected .You get a quench crack and don't notice .Then you HT again and the crack surface forms scale at high temperature .This section has the dark layer and on the final quench the crack extends .The extended part has a clean light color since it hasn't been exposed to high temperature !!

I agree. Wrong terminology on my part. I meant a small crack that I didn't see had formed. As Ray Richards pointed out to me on the phone a little while ago, I probably would have seen it as I began to polish out the blade, if I hadn't broke it in two first.

 

[Dmitry.M]

Well, better to break it in the vice than the customer will break it getting from the sheath. My condolences about broken blade, it looked nice.

 

[mete]

Does anyone check blades for cracks with sound ? A hardened blade should have a nice ring to it .A hardened blade with crack should not have a nice ring !

 

[Will Leavitt]

Does anyone check blades for cracks with sound ? A hardened blade should have a nice ring to it .A hardened blade with crack should not have a nice ring !

Mete, I mentioned in my first reply that I always give my blades a sharp rap on the anvil after heat treat. It's a rather sickening sound :barf:

 

[Steve Hayden]

Does anyone check blades for cracks with sound ? A hardened blade should have a nice ring to it .A hardened blade with crack should not have a nice ring !

I hang them on a piece of baling wire through a pin hole and tap with anothepiece of metal. Good heat treats will ring like a tuning fork. Sometimes you need to change holes to get the best tone. A cracked blade will just clunk-a dead sound.

 

[mete]

Will , sorry I missed that. Apparently some of you do .It's a very simple but effective check for many things, blades ,grinding wheels , your wifes china etc !!

 

[Kevin R. Cashen]

Terminology - that's not a microcrack at 1/8" long. Microcracks can be as short as the diameter of one grain !! I have a photo of one like that in a book but it's not quality enough to photo. What you have is just a quench crack formed in one of the quenches as I suspected .You get a quench crack and don't notice .Then you HT again and the crack surface forms scale at high temperature .This section has the dark layer and on the final quench the crack extends .The extended part has a clean light color since it hasn't been exposed to high temperature !!

Indeed! Here are microcracks:

since the longest of them is less than .02mm I would say that a 1/8" fracture is definitely a macrocrack

 

[scottickes]

I took it over to Raymond Richards shop yesterday and he agrees that it was a quench crack. We put the remainder in a vice and broke it two more times. The grain structure looks pretty good, but it is a dark grey in the crack from seeing high heat. The blade didn't have nearly enough flex. I'm going to up my 52100 tempering temperature and I'm going to also put a thermometer in the oven to get a more accurate reading of my tempering temps. One of the pieces did retain a slight flex after breaking. The blade broke when it was approximately bent to 45 degrees. I'm going to etch it to see if I had edge quenched it (I can't remember...). I'm thinking 45 degrees isn't bad for a full quench, but maybe a little short if I had edge quenched it and had a softer back.

The blade is now in four pieces and will be on the display shelf in my office. After breaking it, Ray handed the pieces to me and stated, "It's now a multi-tool".

Thanks Ray, for all the help and taking the time to visit with me and help me with this.