Blade failure success!

KCorn

Well-Known Member
OK. I finally took the leap and made an entire knife just for the purpose of testing it's performance and then getting it to fail no matter what it took. We had a trip planned to go to Colorado so I rushed to make the knife so I could test it with some good chopping and firewood prep. The 1084 blade is very similar to the Survive knives GSO 7/7. A 6 3/4" blade and about a 5" handle. Micarta scales that attach with torx screws. The top 1/3 of the blade was coated with satanite and allowed to cure for 24 hours then heated to non magnetic in my forge and quenched in maxim fast oil (about 9 sec oil). Then tempered at 425 degrees for 2 hours.

Overall I was very impressed with its chopping and edge holding. It did not maintain a shaving sharp edge for quite as long as I would have liked but there was no noticeable edge rolling or chipping. At the end of our trip my son and I stuck the tip of the knife in a log and tried to pry a chunk of wood out. It really didn't take much lateral force to break about .5" off the blade. We then found a crack in the log and jammed the knife down about 1/3 of the way down and again pulled it to the side. It bent maybe 45 degrees and then snapped clean in two.

My question is this: What do you Dogs think I could do to improve the performance of the next big chopper I make. I know 1084 is capable of more than what I saw with the right heat treating. Give me your suggestions gang. I'm open for anything. Thanks!!
 
you made a piece of well hardened steel, well hardened steel does not bend much past 30 degrees without breaking. try same blade but temper at 325 or so, should have hardness Rc62-63, it will hold that razor edge. knives are for slicing and cutting, axes/hatchets for chopping/wood prep, pry bars for prying.
am i missing something or are knives supposed to bend 180 degrees and chop wood? maybe it's the scar on my forehead from my dad's ring when he backhanded me for using a pre-WW2 sheffield kitchen knife to bend a can lid. Isn't being able to reduce a 2lb cabbage to cole slaw in a dozen stokes then slice a tomato see thru thin good enough? maybe i should have watched more Rambo movies in my formative years.
JMHO of a tired old sailor
 
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If you want a stronger blade, you have to use thicker steel with thicker bevels.
 
LOL. I thought my dad was an only child.....

Yeah Scott, I would rather a blade be harder than able to chop and pry. There are other neat tools for that. Most of the survival knives look like light axes with a horizontal handle to me. And most would be miserable for kitchen work....camping or otherwise.

KC's blade seems about right to me. I take enough other gear camping that I never would need to pry with a knife. I don't have a ring scar on my forehead but my dad didn't tolerate abuse of a knife....and prying was considered abuse.

I can't weigh in on improving that heat treat as I don't have the experience but that sounds like a pretty good blade.
 
here is an idea from chris at wilmont grinders. littleskinner11.jpg the tang has holes that line up on a hatchet size handle and a walking stick sized handle. might contact him at his forum here and see if you can get more info.
as far as heat treat(aldo's 1084), heat to about 1475, soak for 5 minutes, fast quench, temper at 300 for an hour, cold water quench, clean, temper for another hour to get desired hardness 325F=Rc63 350F=Rc62 and so on. would not temper over 400. for some ideas for heavy work knives, look at bush monkey's forum.
 
It's all going to depend on what you want your knife to do. There are large knives/short swords that are built for the purpose of brush clearing that will need a softer temper and maybe a differently hardened or tempered spine. If you want something that will cut up cardboard boxes all day you are going to have to have a harder temper. Still I look at using a knife and a baton to split firewood as doing things the hard way. It will be much easier and faster with a small hatchet. As far as how far a blade should flex before breaking goes, 90° is only for the ABS performance test. Other than that it only shows the balance of strength and toughness and that balance is going to depend on the use the knife is being made for so what does a 45° bend tell us is hard to say. As far as using a knife a a pry bar it's one of those things that gets done but is really abusive of the knife and you can't to it without breaking the point off the knife (I know because I have a pocket knife that 1/2" shorter than when I bought it because I tried using it as a pry bar).

Doug
 
I agree that using a knife as a pry bar is abuse but I think what I am after is a blade that will hold an edge for chopping wood or making kindling and general camp use but will be flexible enough to baton with as well. The ABS test knives seem to hold a phenomenal edge and be tough as well. Maybe I'm asking too much? I like to think that I could achieve that kind of performance with 1084. It is a delicate balance for sure!
 
Kcorn
What did the sections look like where they broke? Where they large sparkley grain, or was it a duller crushed sand kind of look, or was it slick like glass?
I ask because those questions will tell us where your steel was, in a manner of speaking.

For a heavy use knife try this:

Use 5160 steel (1084 if you really want to, or if that's what you have) (Ill send you a piece of 5160 if you would like) steel 1/4" spine (grind or forge to whatever thickness from the spine. Grind or forge your blade. Normalize 2 X, then HT per Scott's instructions. I recommend that you request the HT data EVERY TIME you order steel.(my rule is if they dont or wont provide it, I wont order it! Aldo will provide any data you need on his steel) Heat treat without the clay, if you are using a gas forge, I started using a box years ago and this has helped me a lot.A Piece of thick wall square tubing with an end welded onto it, put this in the forge and let it heat up, then once to heat, put blade in spine down to bring blade to non magnetic. This allows much slower, "therapeutic" if you will heating of the steel. Also helps with decarb. Be aware of not over heating the tip during this part. quench immediately in quench oil. (I prefer to have quench oil directly under and in front of my forge. Quench the entire blade edge first in pre warmed (I use 120 degrees Chevron AAA, but have heard great things about Parks 50! Just too cheap to get rid of what I have!) pre heating the oil is an important step, and makes a difference. Once cool, wipe down and degrease, go directly to temper (also do you use a thermometer in your oven near your blade? You should if you don't). See KNOWN numbers from steel supplier. Once tempered, put the blade into a shallow pan of water. use bolts, chunks of steel, rocks or whatever to set the blade on to have roughly slightly less than a third of the edge submerged in the water, adding a small clamp or vise grips to tang make it very easy. Take a torch to the back of the blade until you reach a nice peacock blue. Let sit until cool. this blade should serve you well as a HARD USE KNIFE, I applaud that you test your knives to destruction, how else do we KNOW what our knives can do! Please be advised that this is how I do it in MY shop, your results may vary, and should to a small degree. If I can be of any help during this process, please feel free to PM me, I can give you my # and talk about it. Not trying to come off as a know it all or a super pro, just an old fart who has ruined a lot of steel to get to where I am! And along the way MANY talented folks shared and still share their knowledge of the craft so I try to do my part and pass it along. Please keep us posted!

God Bless,
Mike
 
Mike....don't bother with Parks 50 on 5160. It's way too fast for that steel. It will get hard...no doubt...but with non-necessary risk of cracking. Parks 50 is really only for the 10xx series, W1, W2, and the like.
 
Thanks for the info Mike. I'll give that a try. I have some 5160 but it is not big enough for stock removal. I bought it to start learning how to forge. I did look at the grain. Seems very fine grained down towards the edge and more course up at the spine. I ran it across a 100 grit belt and then dipped it in ferric chloride to see if I could see any difference. It all looked pretty dark to me. Maybe a little darker near the edge but slightly so. Not sure if that is supposed to reveal anything but I seemed to remember reading that somewhere. What hardness do you think I should be shooting for for a big chopper like that? Why do you say to leave the clay off and draw back the spine with a torch? Would it be beneficial to do both? Thanks again for the help. Great info!
 
Mainly looking for grain size. The smaller the better. These can be really helped by normalizing cycles. If I forge, I anneal my blade before I start grinding, this does 2 things, it helps relieve any stress I have put into the blade while forging, second it softens the steel to its lower RC levels to make grinding easier. To anneal I bring the blade to critical temp then stick into powdered lime that is stored in an old ice chest. If it is a smaller blade I will put 2 pieces of preheated plate in first then put the blade between them. This lets the blade cool very slow.

After grinding I Normalize my blade 3 times.
1.) Heat blade to just above critical (if critical is 1500 Id go to 1550) let cool to touch in still air,
2.) Take to critical let cool in still air
3.) Take just below critical (with our 1500 sample, Id go @ 1400) let cool in still air. This is done by putting in vise by tang or holding with tongs. Don't lay on anything as this will act as a heat sink.. The idea is to cool evenly. Now I would bring the blade to critical and quench in pre heated oil. Some steels need what is referred to as soak times, most simple 10 series steels don't need much. I do roughly 5-7 minutes once to temp if that. The reason I don't use clay on 10 series (although I ALWAYS do on W2 because I'm wanting a visual Hamon) is that it isn't needed, I have seen Master Smiths use a torch to heat the edge with great success and not use a forge at all. There view is if the back of the blade needs to be springy why stress it with a full HT? Me I have had better success hardening the whole blade then drawing the back with a torch or hot block tongs while keeping the cutting edge cooled. And this is done AFTER the tempering cycles, and should be your last HT portion prior to finishing.

On a hard use knife with 5160 Id shoot for the 55-57 range as long as you have a good temper cycle.
For 10 series I might go to 58 but no more.
Edge geometry will also play a role on how your blades hold up. A nice Moran or Convex edge will be stronger than a straight flat grind with a secondary bevel.


As I said before, I'm not saying this is the only way to skin this cat, others have their recipes and they work for them, this is just how I do it.

Good Luck and have fun! PM me if you need some flat stock 5160.

God Bless
Mike
 
Stuart I agree completely.
I do know folks that use Parks 50 for everything and do good with it, I just cant justify the risk.
Probably why I still haven't tried an interrupted water quench on W2!

God Bless
Mike
 
Remember that the ABS performance test allows no cracking past a certain distance from the edge and it's not intended to say how a blade should be made other than for the ABS performance test. If you want to make a blade that you can baton through a piece of firewood, fine. Just be aware that you will probably have to give up some edge holding ability to avoid chipping out the edge. Also steel selection will play a roll in performance. Something like 5160 would be better than 1084 and 9260 would be better still if you can find it, especially if you edge quench the blade as there will be more ferrite distributed in the pearlite of the unhardened spine. Also a convex edge will put more steel behind it and a courser angle more still.

Doug
 
I heard something the other day I really like, "Geometry cuts.....heat treat determines how long.".

Roman Landes. A good friend, a great scholar and author of the book "Messerklingen Und Stahl"

On the ABS test blades, I can't think of anybody in a position to speak for the ABS goals and objectives (I have a pretty good perspective there) who would say that the idea of bending a blade is an indicator of a good knife. The test is instead designed to display the smiths ability to apply various heat treatments, selectively and well controlled, all in one blade. I am also a practitioner of martial arts and so often explain it like this- Forms (poomse, kata etc..) are an excellent, stylized/standardized way to show judges your mastery of techniques under formal testing conditions, but would only get you robbed, thrashed or put in a hospital if you tried to use them in a real world self defense situation. An ABS test knife is a form, it demonstrates to the judges all the techniques you need as a smith in one standardized package. To then make good knives, for real world use, you will use these skills separately or in combination to produce the tool best fit for the application. Since 1998 I have been one of the guys that the ABS asks to teach people how to pass that test and I have been a Judge for Journeyman and Master, the blades that pass the bend the best are not what I would want for fine cutting over the long haul; large choppers that I don't mind sharpening more often, perhaps. But edge quenched blades (not clayed but merely edge quenched) in class, and in practice of the bend test, seem to work best, and yet can rarely keep up with knives made specifically for cutting over the long haul with no concern for bending. Believe it or not, cutting two 2X4's is really not much in the way of performance, but it is the minimum expected of a test blade.
 
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Ghanks again for the info guys. So would it be best for a large chopper to apply clay and achieve a softer spine that way or to only heat the bottom third of the blade with a rosebud and fully quench the entire blade? I guess im looking for more of a spring temper on the spine than fully soft like an ABS test blade. I guess i could also fully heat the entire blade and then draw the spine back to spring temper with a torch. Lots of choices here i guess but thats the challenge that makes knifemaking fun!
 
Samuraistewart is right. If you want a flexy blade, thin geometry flexes. I have thin paring knives that easily bend past 45-50deg without problems. I don't get the super thick blades people seem to like nowadays. 3/16" is thick to me, and will only use it if the customer insists. Full martensite with drawn back spine, no stress risers from design or poor finishing, and a full flat grind with a convex edge will be a superb performer in a camp situation. Well done heat treat with proper normalizing and grain refinement cycles will get the most out of the steel.
 
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