Blade Break Help, and HT question

J. Hoffman

J. Hoffman

Knifemaker / Craftsman / Service Provider
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Jan 1, 2011
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I just finished this chopper for myself. I planned on using this for work. It's 1095 with micarta, nickel corbys and copper tubes. I put a nice convex edge on it, and took it to a 2x4 to see how well this chopper actually chops. Well, you can see the results. After about 6 chops I ended up with two big chips missing. I think the grain is pretty course, but I guess I don't have anything to compare it to. I have a kiln coming, along with some Parks 50 so I hope this issue will not rear it's ugly head again. Can anyone tell me what the likely issue was? Any and all info is appreciated.
 

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Shit man, that ain't no chip. Closer to a chunk.

So, how'd it chop before the chunk:D? Grind looks a little thin for a chopper but it's gotta be the H/T. Since I know pretty much nothing take this with a grain of salt:rolleyes: I think when you were grinding it, you got it too hot.

That or the H/T was shit to start with.
 
I have had that happen to me a few times when I used my forge to heat treat 1095 . I bet if you put that in a vice and gave it a quick little push it will snap in half. Once I got my Kiln and some parks everything was fine. I know its a bummer when this happens . But when the grain looks like table salt you know bad things happened.
 
Yep, I'm far from an HT expert but first thing I saw was how coarse the grain was. Ouch. At least it wasn't a customer knife and they weren't the ones to find it. Guess this shows the importance of test cuts, especially if you are using less controlled HT methods.
 
sirupatespecial said:
Shit man, that ain't no chip. Closer to a chunk.

So, how'd it chop before the chunk:D? Grind looks a little thin for a chopper but it's gotta be the H/T. Since I know pretty much nothing take this with a grain of salt:rolleyes: I think when you were grinding it, you got it too hot.

That or the H/T was shit to start with.
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The first couple of whacks were very good actually. I couldn't figure out why it quit cutting so well, and then I looked at the blade and saw the chips missing (ok, they are chunks):D. Yes, the blade is a little thin for a chopper, but it was an extra hunk of 1095 I had, and I didn't know what else to do with it.

COUNT: thanks for the info. I guess I figured I didn't let it soak long enough, but maybe it was too long. I was pretty careful when I was finish grinding after HT. I'm really looking forward to the kiln and good quench oil.
 
Heat treat on this one was done in a forge. I brought it up to non-magnetic and then let it soak a bit longer. I quenched in mineral oil that was up to about 125 degrees. Temper was 375 for two hours, twice. I put the knife in the vice, and snapped it in half twice more. The first break was in the middle of the blade, and it easily snapped clean. The second time I broke it was just behind the plunge and it bent a lot before snapping. It was much harder to break the second break. I can't wait for my evenheat and Parks 50 to be here!
 
J. Hoffman said:
Heat treat on this one was done in a forge. I brought it up to non-magnetic and then let it soak a bit longer. I quenched in mineral oil that was up to about 125 degrees. Temper was 375 for two hours, twice. I put the knife in the vice, and snapped it in half twice more. The first break was in the middle of the blade, and it easily snapped clean. The second time I broke it was just behind the plunge and it bent a lot before snapping. It was much harder to break the second break. I can't wait for my evenheat and Parks 50 to be here!
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It sounds like you had a very brittle blade with high hardness and low toughness. Isn't that what happens when you don't temper at a high enough temp or for too little time? You would be left with too much retained austinite, large grain structure, high hardness and brittleness.
 
What is your normalization protocol? Did you forge the blade when it was too cool?
 
What is your normalization protocol? Did you forge the blade when it was too cool?
 
91wm6 said:
It sounds like you had a very brittle blade with high hardness and low toughness. Isn't that what happens when you don't temper at a high enough temp or for too little time? You would be left with too much retained austinite, large grain structure, high hardness and brittleness.
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ETA- how long did you wait between quench and tempering?
 
I think your main problem is that you do not make enough or non normalizing cycles, as i can see from the fotos your grain is not so fine,secondly you probably have a very short soak time at critical temp
 
If you are not doing a hamon, then why have you chosen such a fast quench steel? This is typical 1095 bullsh**. Switch to 01, and never worry about it happening again.
 
Your procedure doesn't seem to be terribly out of whack, but that grain sure looks like the steel was overheated before the quench.

Fiddleback said:
If you are not doing a hamon, then why have you chosen such a fast quench steel? This is typical 1095 bullsh**. Switch to 01, and never worry about it happening again.
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I agree with Andy. I do not understand the fascination with 1095 at all, especially from handmade/custom makers (barring hamons of course...) Once you have your kiln and proper quench oil set up, you will get better blades out of O1 with less problems. O1 is affordable, easy to work with, very satisfactory and pleasing to "traditionalists", it takes a beautiful crisp edge easily, and it's quite tough. :thumbup:
 
The tempering temperature was good, assuming 375 was really 375 and not 275. Tempering won't grow grain size. That happens during austenization before quenching. I couldnt see the grain size too well in the pics, but if its as large as some indicated (looks like sugar) it was likely overheated and then not repaired. If you had known, it could have been cycled and the grain shrunk.
 
The grain should have a satin look to it... yours does not. You simply overheated it. Consider using a muffle pipe set up in your forge, don't try to soak, keep the blade moving in the forge with a pumping action, get it to fully non-magnetic and pump it for another 3-5 seconds, then quench. I would also go with canola oil rather than mineral. 1095 is a tricky steel, especially if you are forging.

Optimally, you would want temperature control and an engineered quench oil... which you sound like you are trying to get.

Keep having fun and your knives will get better as you make more mistakes:thumbup::p
 
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In addition to the overheating (supereasy with the narrow range 1095 works in) the tempering is too low. 350f would leave you at Rc 63 or so. 450-500f would get you into the high 50s, where you probably want to be with this knife. That won't fix the overheating, but would decrease the brittleness. Take a piece and temper it at 500 and see if it still breaks as easily for an experiment.
 
I was wondering about the 1095 too until I saw that it was an extra piece you had left over. I like it on the small knives that I have using the steel, but I'm switching to o1 since I've been having such good luck with it (on knives I've had made. No direct experience using it myself. Yet.). 1095 has always been my favorite steel, but I have had issues here and there. Not so with o1.

Sorry that happened to you. Great learning experience though. Congrats on the oven, should take your ht to a much higher level. :)
 
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