Video of my first 90 bend flex test.

mlovett said:
. I want a blade that will just about rip the vice off the table. .
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Strange that you should say that...
There are 3 bolts that hold my vise to the workbench.
However the workbench table top is just one 1/2 inch sheet of plywood, and that plywood is not actually nailed or bolted down very good to the supporting 2X4 legs.

Rather the plywood is just setting on top of the frame of 2X4s, held down and in place by the weight of the mess of my tools that lay on top of it.

I forgot all this when I started to do my test.
But about 1/2 the way into the test I remembered and felt lucky that Im such a pig that I had left so many tools on the workbench.
 
thanks, I am going to try to remember to test another knife in the summer to see how things are going then too.

I hope my next video clip I share here is not one with the darn heater blowing so loudly in the background.
 
I'm glad to see you were wearing safety glasses. :) Back when I was still bending blades, I had a shard of steel fly off and punch a hole in the aluminum siding of my workshop. :eek:
 
BTW, your assuming that a through hardened blade is actually going to break during use. I suggest you try it. Make another blade like the one you just bent, harden it all the way through, and try to break it in your vise. Good luck. :)
I tried it a couple times, and the only way I could break it was by sticking just the very tip in the vise. That's with using a 2 foot cheater bar. When I tried putting it 1/3 of the way in the vise, it started pulling the workbench (which had a couple hundred pounds of scrap steel and wood stored on the lower shelf) over.
 
The glasses?....

Ahh yes, you see I knew I would be posting the video on to YouTube and I didnt want 40 comments about how dangerious it was and how I should have known better to not wear glasses.....LOL

(also, my mom was going to watch the video and she got me the new glasses for Christmas as a stocking stuffer)

If you have seen my short video clip of the forge work for that test knife, http://www.youtube.com/watch?v=TzJ-91nUhPA you will notice that I also forge with the glasses on.
This I "HAVE" to do because of all the flux the sticks to the ball bearing in the forge.
Each smack with the hammer sends it flying all over at first.
 
Phillip Patton said:
BTW, your assuming that a through hardened blade is actually going to break during use. I suggest you try it. .
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I did, I dont have it on video but I have found that a blade that I hardened too much broke right away in a pre-test of my torque wench clamp.

I made the clamp based on a photo I once saw in BLADE mag.
However Im not a welder and so I didnt trust my welding on the clamp to hold during the test.
I also used two bolts to hold both sides of the clamp onto the knife blade, but I had to use the smallest bolts I had because they fit the biggest holes I had drill bits to make.
While getting ready to do the test I did a dry run of my torque wench and clamp to make sure they would stand up to the task.

I had a annealed blade of 52100 that had a bad tang that I gave up on, so I decided to harden it and use it to work out any bugs with my torque wrench setup.

But rather than going to the trouble of waisting O/A gas for the torch, I just fired up my forge and heated the whole blade.
Then I dunked the whole blade in the quench oil.

It snapped right away.

Thank GAUD I had been warned about how to do a test and so I was pulling the torque wrench down to me at the time.
Had I been pushing the wrench over the top of the vise I might well have stucked the broken blade into my chest...

I understand that some guys like to fully harden their blades, I just think that for a working man who might face jobs where they will need to put their blades to the same torque as I have, that a stronger back spine that will bend rather than break is needed.....There is no question now after my testing about it in my mind...

Now the idea that you fully harden a blade because you dont want it to bend very easy , well, to me thats crazy.
Im not really interested in the blade not ever bending, IF that means that i raise the risk of the blade snapping on me too.

I have been reading over the past year on the forum that some knife makers like to use a design that aims for a blade that is fully hard because they dont want it to bend as easy of a edge-only hard blade.

And yes, I understand that a fully hardened blade is harder to bend than one thats edge-only hard.
But so what?

It only figures to me that if I made the whole blade just as hard as I made my cutting edge, that the blade would be a lot harder to bend at first..
But, again so what?

The more important matter is that the same problems we all have with the hardened edge being more easy to chip, crack and snap would just get carried over into the rest of the blade too.
Well who wants that?

Thats not the direction I am going...

I want a blade that can cut to be sure, so I need a very hard edge.
But a blade you also can trust will not snap on you just because you over-torqued it and the edge has chipped or cracked .

Bends I can fix with a hammer....
Cuts from a broken blade?,,,not so much.

So do I believe I should design my future blades to bend?
no.

I believe the bending is just an effect of the true design aim, and thats to make a blade that will not snap on a guy.
Bending just seems to me to be an outward sign of the inner nature of where the steel is at.
I dont design my blades to bend.
Bending is not my real goal.
I have never needed a bent knife on my job in my life.

But what I have always needed is a knife that can cut, and that will not let me down in a pinch...I need a knife I can trust will not snap in two on me just because I pushed it over the limits...
because I will always be pushing the limits, thats what working men do.
We dont just torque on a blade untill we think it's about to break,,,
we dont stop short of the designed limints of the steel...
We go for it,
we use the tool in ways it was not meant to be used...

Thats the way normal life is for a knife.
 
Might be a stupid question, but I always have heard hardening the entire blade makes it brittle. As Alan Molstad has said and tested, this comes out to be true.

So...why would a fully hardened blade be more desirable? It's either perfectly straight, or snapped in two. Wouldn't you WANT a blade that is more flexible, and if bent could more easily be brought back to center? Like I said earlier I'm not a steel expert, so maybe I'm missing something.
 
In my reading about the sport of Kendo, and the history of the japanese bladesmiths, I have learned about how the smith will take a very high carbon steel thats very breakable, and wrap it around a low carbon steel thats very strong and will not break.

They also clay-coat the blade in such a manner as to add to this effect of strong joined next to hard.
This gives the result of a sword that is hard along the cutting edge, but strong along the spine .

I think for a real working man who needs a trustworthy knife at his side, we should also seek to design a blade that also offers this type of hard edge connected to a softer yet strong spine,

To me it seems the best way to go...
 
Alan Molstad said:
I did, I dont have it on video but I have found that a blade that I hardened too much broke right away in a pre-test of my torque wench clamp.

I had a annealed blade of 52100 that had a bad tang that I gave up on, so I decided to harden it and use it to work out any bugs with my torque wrench setup.

But rather than going to the trouble of waisting O/A gas for the torch, I just fired up my forge and heated the whole blade.
Then I dunked the whole blade in the quench oil.

It snapped right away.
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The blade that you broke, did you temper it?


4W4K3 said:
Might be a stupid question, but I always have heard hardening the entire blade makes it brittle. As Alan Molstad has said and tested, this comes out to be true.

So...why would a fully hardened blade be more desirable? It's either perfectly straight, or snapped in two. Wouldn't you WANT a blade that is more flexible, and if bent could more easily be brought back to center? Like I said earlier I'm not a steel expert, so maybe I'm missing something.
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Hardening the entire blade does NOT make it brittle. Not tempering it properly, or having coarse grain, WILL make it brittle. A fully hardened and well heat treated blade will require more force to break than you're ever likely to exert on it during even extreme use.
 
Alan Molstad said:
In my reading about the sport of Kendo, and the history of the japanese bladesmiths, I have learned about how the smith will take a very high carbon steel thats very breakable, and wrap it around a low carbon steel thats very strong and will not break.

They also clay-coat the blade in such a manner as to add to this effect of strong joined next to hard.
This gives the result of a sword that is hard along the cutting edge, but strong along the spine .

I think for a real working man who needs a trustworthy knife at his side, we should also seek to design a blade that also offers this type of hard edge connected to a softer yet strong spine,

To me it seems the best way to go...
Click to expand...


They also often left their blades full hard, as in not tempered...
 
First, Alan if the ABS test is the direction you are heading in I would like to say congratulations on a good start. Phillip I cannot tell you how pleased I am to see your progress as I am sure you will have a stamp soon. But even more fantastic to me is how you have a firm grasp on the actual physics behind this and how steel really works, the fact so many fresh talented faces are clearly seeing through age old, universally accepted misinformation gives many of us much hope for the future.

Now about the concepts of the stregths of full hardened vs. edge hardened blades, I know I must have droned and harped about it here in the past, and I don't want to hijack or take anything away from Alan's thread. Perhaps I could add a stress/strain curve to the other curves at the top of the forum and we could get into the realities of strength and ductility. Visitors from this forum that attended Tim Zowada's bending/breaking lecture could contribute much about seeing it with their own eyes (I should have made Tim let me do the gadget lecture:grumpy: , but alas it may be my fate to do the Ashokan heat treat lecture for all eternity.)
 
Right now Im in the middle of finishing two knives for my boss, I also have a co-worker that I have to finish a knife for.
At my jobsite there are about 20 some guys who hunt deer in the fall.

Now the reason I have to make my guys some new knives for next year is that all 3 knives they own snapped on them this year.

Hunters always seem to break their knives in the same spot on the deer, where they attempt to break a bone rather than use a saw, (as they should )

What they do (what we all do) is jam the blade or the tip of their blade down into the hard deer bone where it will finally get stuck.
At that point the normal thing to do to try and free the blade from being stuck is to twist the blade out.

The blade might pop free,,(It could happen),,however for 3 blades this year and for many other in past years, what normally happens is that the blade snaps off.

Why?
Who was at fault?

We all may have differen views of that answer of why the blade failed, but when I look at this situation I see a different answer.

This last year when my boss told me how he broke his blade, what went though my mind is that concept that even if the blade was never designed to cut bone, it still should not have snapped like that.

There is a difference between being a poor bone cutting blade, and being a breakable blade.

If we are to design true working man's blades, then we dont need to worry that they are always going to finish cutting things like bone and iron and cement.
However a good knife should not end up in two sections just because the guy attempted to cut such things...

Because working men will always try to cut bone, iron, and cement sometimes,,,for thats what life brings us sometimes...LOL
 
Alan Molstad said:
...I have learned about how the smith will take a very high carbon steel thats very breakable, and wrap it around a low carbon steel thats very strong and will not break...

...They also clay-coat the blade in such a manner as to add to this effect of strong joined next to hard...

...This gives the result of a sword that is hard along the cutting edge, but strong along the spine...

...I think for a real working man who needs a trustworthy knife at his side, we should also seek to design a blade that also offers this type of hard edge connected to a softer yet strong spine,...
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Alan just one last point (that I can't let go) and then I promise to leave your thread alone. Soft steel is the opposite of strong, since it is ductile. Your blade will be every bit as in demand as the next guys and I believe you will find success as ductile spines is very much in vogue these days, but the word you are actually looking for to desribe ductile steel is "tough" not "strong". Fully hardend steel is the "strongest", dead soft steel is the "toughest". Folks often confuse these two, but they are lucky if I get to them first, I may not be able to protect you of mete catches you using tough and strong interchangebly;)
 
Phillip Patton said:
Hardening the entire blade does NOT make it brittle. Not tempering it properly, or having coarse grain, WILL make it brittle. A fully hardened and well heat treated blade will require more force to break than you're ever likely to exert on it during even extreme use.
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Oh, then I mis-interpreted the word "hardened". Right now I'm reverting back to my katanas and what I remember reading on a sword forum a few months ago. Sword and knife steel is really quite different to me haha.

They also clay-coat the blade in such a manner as to add to this effect of strong joined next to hard.
This gives the result of a sword that is hard along the cutting edge, but strong along the spine .
Click to expand...

If I remember right, that is also what gives the blade that natural hamon look. At least, the "real" hamon. So maybe we will start seeing knives that look more like tanto's? I'm not sure I've ever seen a production utility/tactical knife with a visible hamon.

Because working men will always try to cut bone, iron, and cement sometimes,,,for thats what life brings us sometimes...LOL
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As is the most common test for a good katana. Swing it at metal polls, chain mail, cinder blocks, small tree branches, etc.

After cinderblocks...
chips2.jpg
 
I think what I get out of my 90/180 flex test is that it helps me see that Im on the right track.

I have been reading so long about the testing found in the ABS that I always questioned, "Could I pass that test too?"

It's nice now to have some sort of answer to point back to as I go into the future.
It's nice to know that the only real data I have to show me how Im doing, is telling me that Im on the right track and that this is the direction i wish to go in.

In the future people have suggested that before I bend-test a blade I first do some cutting tests on rope. I will try that next time. Im a little concerned that that type of cutting test might only show my lack of skill at getting a blade sharp, but then too, that also is something to learn and to remember as time goes along.

On this topic the idea of the japanese bladesmith was introduced, and while I dont think a guy should need to weld two different types of steel into a normal knife just to end up with a trustworthy blade, still, now that I think it over more, it would be an interesting thing to try.

One of the ideas i have had concerned the way the japanese smith would drag clay down from the spine , down to the cutting edge to mix stronger form of the steel into the harder.

I would like to see if a guy could do this with two different steels. somehow bring small amounts of the strong steel down into the hard without screwing up the hardened edge...also, the ability to drag a different hard steel up into the spine to stiffen it yet not effect it being unbreakable,,,,,

Just an idea I have had at of late...

Anyway, as I said, it's nice to have finished my first 90 flex test on this note, and with luck i will be able to do the same test this summer and find things have imporved too.
 
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?"
 
4w4k3....
From what I have learned just from reading about the japanese katana....the reason you and I never see true hamon in most American-made blades, is that it takes a lot of sanding work of many stones to bring out the hamon in the japanese manner.

What we see a lot is swords that have been etched to show the hamon.
There are many American bladesmiths that can make a sword to match any made in japan,,,the problem is, that the future owner, (Or the maker) has to have some deep pockets to pay for a the more traditional way of sanding down with paper-thin stones to show the hamon.
 
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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If you mean my blade?
If you watch the video, You will hear that i became concerned at the amount of time I took to do the test. I was not sure what the time limit of YOUTUBE was, so I just ended the test and went into the house to warm up.

The next part is not really going to tell me much.

I didnt go out into the shop for about 8 hours...the blade sat into the cold (- 20 below zero) all that time,
Does that matter?...I dont know...does that make pointless any more 90 flex bends?..I dont know.

But when I did go back out I just wanted to fool around and do more flexing of the blade, two 90 bends later I saw the crack, another bend or so later I saw another and then I just wiggelled the blade back and forth to snap it off.
When I saw the first crack, was that the first moment it was there?...I dont know
Could the crack have been there, but unseen even during the flex test/...i dont know.

In the video you see me look for a crack, I didnt see one, I didnt hear a 'ping",,,but I will have to pay closer attention next time looking for hidden cracks...

Im not sure any of that cracking means anything....
It seems to me that no matter what type of heat-treatment you do to a 1/4 inch thick steel, that bending it back and forth long enough will cause it to crack....

Im not sure I see the point in that part of a flex test.
I am more interested in the fact that Im now able to use a torch.in such a way as to make a knife that is sharp, yet not so hard that it snaps on me when i really over-torque it to death....

Doing the 90 flex was the only part thats important to me...That told me right there what I wanted to know.

bending the blade back to straight in the 2nd video clip was just an "interesting" thing for me to try...I just kinda wanted to know if I could do that or not?

But the flexing to 180 was just for show...I dont think it tells me anything more than what i learned in the first video at the end of the 90 flex...

However,,,,,as a way to show off to the guys at work,,,it's priceless!
 
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