Video of my first 90 bend flex test.

If I remember correctly, at one point in your video you comment that the edge had not cracked.

My comment was not directed at your blade but to make others think through what they are seeing, and learn how to question things to increase understanding. "Why did the hardened portion not crack?" is an important question I think.

Alan, I am happy for you that your blade met and exceeded your desired performance. I wish you well with your experiments. Learning new things is always wonderful and understanding them makes us better knifemakers. Thank you for sharing the video! :thumbup:
 
fitzo said:
I'm a little surprised that no one has yet raised the question of "Why, if hardened/tempered steel is so very brittle, didn't the edge crack during all that abuse?"
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Good point. :) The spine will put up with anything the edge will.
 
fitzo said:
If I remember correctly, at one point in your video you comment that the edge had not cracked.

My comment was not directed at your blade but to make others think through what they are seeing, and learn how to question things to increase understanding. "Why did the hardened portion not crack?" is an important question I think.
:
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Yes, I dont have the understanding to answer such a question.
You take some steel, and attempt to make one side of the same small section of steel as hard as the limitations of that steel allow for.

and all the while you do that, you are aiming to not harden at all some steel that right next to the part you want hard.

Then you attempt to bend both in a way that must effect both parts in different ways, yet both parts must stay connected?....

beats me how it works.
 
I have a question for you guys...

with most knife steels...does outdoor cold effect them in bad ways?

yesterday it was very very cold here...would such cold change in any real ways that a guy would notice, the things his knife would do or not do?

Does a blade have more chance to snap at -20 or more below zero?
Lets say you were cutting firewood with your knife. and the knife snaps off at the handle.

If it were summer and +99 out side would you blame the heat?

If it were the dead of winter and it was about -40 below zero would you blame the cold?
 
I think it was a while ago here there was talk of some type of steel used in the far northpole area that was uneffected by the cold.

But what is the temp range where cold will effect a normal knife blade in a way that you and I would notice?
 
mlovett said:
I want a blade that will just about rip the vice off the table. But that is just Me.
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Thats exactly what happened to me last week...a fully hardened and tempered bade...(3 inch blade)....I wanted to snap it just to check the grain growth as I had been doing some experiments on soak times.......vice couldnt take the stress and the cast iron ripped apart just above the bolts that clamps the bolt to my steel work bench.
 
My first little vise was from Wallmart or Kmart , and was also cast iron,
I broke it also attempting to take appart a pipe fitting.
I had the female part of the pipe fitting in the jaws of the vise and was useing the pipe wrench to turn the male pipe out, when the whole vise broke right out of it holding bolts...

What was going to be a 30 second fix, turned into another all-day deal.
 
Alan Molstad said:
I think it was a while ago here there was talk of some type of steel used in the far northpole area that was uneffected by the cold.

But what is the temp range where cold will effect a normal knife blade in a way that you and I would notice?
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I think it was welded cable. (1080)
I can't answer your question, but I suspect most steels, if they're properly treated, would hold up fine in most climates we have in the lower 48 states.

I remember reading a thread where someone suggested that the reason steel tools break in cold weather is because of retained austenite, which the extreme cold converts into untempered martensite, which would be brittle. Don't know if there's anything to the theory, but sounds good.
 
An early knife I made from fully hardened 1084 before I had the heat treatment down better still required me to expend an enormous amount of energy to break it. It didn't make it to 90 degrees, more like 60 degrees and it broke because I had overheated the steel which was evident from the size of the grain which wasn't bad, just not ideal. If it had been heat treated properly I doubt I would have been able to even bend it to the point it would actually break without fear of doing great bodily harm to myself.

I have made knives both ways and my opinion on the hard edge/soft back isn't so much that one form is better than the other, just different ways to make a dependable knife. On that note, if I did use a knife with a differential heat treatment and ended up bending it to a great degree I wouldn't trust that knife again for a similar situation even after straightening it back out because the damage is done and any more bending would only further weaken the blade. So yes, in a survival situation having a blade that would bend before breaking might be a plus as you would still have a viable blade to use, however it might be better to have a blade to which you were highly unlikely to be able to apply enough force to break in most field situations. In my opinion which probably isn't woth much, for day to day normal to heavy use, including using a knife for what it wasn't intended, I find it likely that both types of heat treatments would hold up without either bending much or possibly breaking.

Anyway interesting topic and congratulations Alan on being able to perform a heat treatment on that blade that allowed your bending test to succeed. You made a very tough knife! I'd also be interested in knowing what types of knives your buddies had that broke on them. My guess would be production blades left deliberately hard for better edge retention.
 
The reason I ask about cold...

I dont do any of that stuff where you place the knife in the freezer between Heat-treatment steps.

I just dont know enough about such things.
However I also have read that some guys who know steel look down of guys who use a freezer,,,
on the other hand some guys have writen all sorts of scientific reasons why the freezer might help.

I dont know whats true in that case
,
However I have also read about guys who go to cold places like the NorthPole and they like to use knives that are not subject to snapping in the cold.

If the cold at the Northpole can effect a blade so much that you have to watch what changes might happen to the blade steel, then it kinda figures that even my kitchen freezer has a mild effect on steel...good or bad?..I dont know, but it would stand to reason that the cold changes something...

If thats the case, then what is the effect (if any at all) on testing a blade that left out in a cold unheated shop (-20 below zero) compared to a knife taken fresh from the house and tested?

No way to know?
Some difference possable?
no difference at all, ?

You tell me...
 
Guy Thomas said:
I'd also be interested in knowing what types of knives your buddies had that broke on them. My guess would be production blades left deliberately hard for better edge retention.
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I dont know yet,,,,I was told that they each had a broke knife that had to replace this year anyway...

I should also get them one of them little saws for cutting that bone that always seems to cause the main trouble for hunter's knives.

My guess is that due to the "BIG DEAL' deer hunting is to my co-workers, how they spend tons of money on their guns, hunting land, new pickups, and beer every year just for hunting, that the kinfe each uses is the best they can get...more than likely a BUCK knife...

BUCK is seen by most hunters I know as about the best you can get.
 
You clamp a blade in a bench vice and bend it back and forth with the assistance of a torque wrench or breakover bar to see if it will break. Assuming it would have a decent edge that would cut, the end result would be that you have a bent/broken knife that is unusable. Good test :cool:

What kind a meniacal hunters you makin knives for anyway:confused: :eek: :D

Here's how I test my knives: I clamp a blade in the bench vise with the edge out horizontal and then flick a frozen booger at it. If it slices in two, the knife is good.

Not really...I just made that up cos I'm a dork. But seriously, that's alot of hard work to just hose up the blade to see it do what you know what the result would be anyway. The blade's gonna end up bent and/or broke after that test...ie, unusable. A similar test would be to see what would happen to a 1/2 ton pickup, lets say a CHEVY, and placed a 5 ton bolder in the bed....unusable.

Seems to me if somebody breaks a knife that is properly made then they were doing something with it they ought notta been doin. What was the knife that your boss broke anyway? I would like to see THAT video. :D Flying guts and crushing bones sounds way more interesting than bending knives. :cool:

Remember what the Chief of Police said on the movie Jaws when he ws chumming and first saw the shark from the back of Quint's boat. He said, "We're gonna need a bigger boat". Well it wouldn't have been as funny if he said, "I don't believe we have the proper tool for the job", but that's what he was getting at.

That said, I agree that it looks like you know what you are doing and you are following sound advice and learning good forging and tempering techniques. FORGE AHEAD!:thumbup: :thumbup:
 
Alan Molstad said:
I dont know yet,,,,I was told that they each had a broke knife that had to replace this year anyway...

I should also get them one of them little saws for cutting that bone that always seems to cause the main trouble for hunter's knives.

My guess is that due to the "BIG DEAL' deer hunting is to my co-workers, how they spend tons of money on their guns, hunting land, new pickups, and beer every year just for hunting, that the kinfe each uses is the best they can get...more than likely a BUCK knife...

BUCK is seen by most hunters I know as about the best you can get.
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Yikes, they need edumacatin! I had a Buck hunter that I pryed something with......ONCE.
 
Kerry Hampton said:
A similar test would be to see what would happen to a 1/2 ton pickup, lets say a CHEVY, and placed a 5 ton bolder in the bed....unusable.

:
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Well, actually, thats true.
If I was the guy who designed a Chevy truck, I would take one of the first off the line, and add 5 ton of rock to the bed, and tell the driver to drive the truck untill the thing breaks down.
Then you would know what the truck can take and what will break first when it is overloaded.

Testing is where you ask a tuck or a tool, or something to go way past what would be normal for it's future,,,go push the limits...to go to the very point it fails...

thats how you learn where the stopping point is.

Thus, before I looked at trucks, I would enjoy reading about the testing-to-the-point-of-broken, that a truck design was put to...

They make ARTIC CAT snow sleds where I live.
Out at the test track you can watch the guys running around on the track all winter, banging the stuffing out of the sleds,,,,going and going over rocks and rail road tracks until something breaks.
When it breaks or fails, thats when you learn.....

Another example: Cutting Tests.
Im told that on my next set of tests on a knife blade that I should first do some cutting tests to check the ability of the edge to stay sharp under stress.

OK, so I will get some rope and start to cut it.

Now thinking about it, how many cuts of this rope would represent my own lifetime worth of rope cutting?

Well, in my own case, I would guess that after the 6th cut of the rope you have reached the total number of cuts I have ever made on any rope...

I just dont cut much rope....

so why then keep cutting another 100 times?
I think the answer is that , this is how you get to learn about the knife some new information..you ask it to do in a test what you will never ask it to do in normal life.
 
Guy Thomas said:
On that note, if I did use a knife with a differential heat treatment and ended up bending it to a great degree I wouldn't trust that knife again for a similar situation even after straightening it back out because the damage is done and any more bending would only further weaken the blade.
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LOL. I was watching my 2nd video clip of the 180 flex, and I remembered this.

I was stunned that I was able to bend the knife back to straight.
And i also noticed that I had bent it back, more-or-less in a very close to true position.

And just for a moment, I thought about stopping the flexing and just saveing the blade to really have.

I was thinking about how would a guy 'fix" a bent to 90 blade?
My guess is that a single full heat treatment and temper would return the blade to normal strength.
Bending to 90 is bad for a blade Im sure, but so is banging on it during the forging too, so it should be fixable right?
 
Alan Molstad said:
Well, actually, thats true.
If I was the guy who designed a Chevy truck, I would take one of the first off the line, and add a ton of rock to the bed, and tell the driver to drive the truck untill the thing breaks down.
Then you would know what the truck can take and what will break first when it is overloaded.
Click to expand...

Not fare! You altered my test. I said a 5 TON rock. Even a 1500 Chevy truck will work for a long time with a ton of gravel in the bed. 5 Ton would cause the springs, and probably the axles, to bend alot and/or break.

That is analogous to the 90 degree flex test I think.

Knives s'pose to cut first, bend a little second, and then after that is a WAG depending on who's on the handle. End user is a big variable. I understand you're just trying to make the knives more idiot proof.

You're way ahead of most folks in understanding the correct properties of a properly tempered blade. Keep up the good work.
 
Kerry Hampton said:
Knives s'pose to cut first, bend a little second, .
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I really dont think us knife makers should design our knives to bend.
The bending seems to me to just be an after-effect of the true aim of the design to not snap on a guy when he needs it most.

I believe that first , a knife should be able to cut,,,if it cant do that its a bit pointless.

But next to the ability to cut, we should also think about the way life is.
You cant say to yourself, "Odds are that the owner will never apply so much torque to snap the knife."....because thats just not the way real life works out.

All the time I have owned my truck I have never once even come close to an accident. Yet I still tell everyone to "Buckel up" when they ride with me...Why?
The odds are that , as my history has shown, I will never get into an accident with that truck.
The odds are that with the great design of the truck, the hight, the good breaks, the good tires, the good stearing system that it has, that I and my riders are totally safe from harm without the pointless seatbelts being used.

But I also know one little thing about real life...If the odds that a knife blade will break on a guy are a million to one, then you can bet that when it does fail it will be in the dark, down in a sewer, with your hand under some very dark water...with no way to know what just went "ping" ....

Thus, I believe as I learn how to make knives,that I MUST take into carefull concideration the way life is,,,,and try to make my blade one that I can trust,
 
Alan Molstad said:
I was thinking about how would a guy 'fix" a bent to 90 blade?
My guess is that a single full heat treatment and temper would return the blade to normal strength.
Bending to 90 is bad for a blade Im sure, but so is banging on it during the forging too, so it should be fixable right?
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That's a really good question and not one I have a good answer for. I have no idea how a new heat treatment would actually affect metal fatigue like that but I'm not so sure it would return it to it's original state. Hopefully one of our more knowledgable members could address that. I'm curious.
 
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