edge quench

S

soundmind

KNIFE MAKER
Got a chance to experiment with heat treating this morning. My 4th time practicing an edge quench. Just wondering if my procedure is right - Tip first then rock back?

Every time I've done it this way the blade cools too much near the ricasso and hasn't hardened in that area - just making sure if I'm doing it right.

Thanks all
 
Just got done teaching and ABS Intro to Bladesmithing course, where I have to oversee plenty of this and, as I always say, a little part of me dies every time I have to teach edge quenching, but we do what we must. Full edge in on the limiter plate first for a one second count and then rock up for a second to get the tip. I think I am going to start taking a tub of furnace cement to my Intro classes so the we don't have to worry about this at class anymore.
 
Just do not put it too close to the edge I have noticed the “softer” area as designated by an acid etch will extend a little past the actual “line” you make with the furnace cement. Also, how are you heat treating? Kiln, torch, forge etc?
 
I think that this arises out of the flex/bend test on the ABS test blade. People start thinking that this is how a superior knife blade is made. What it is is a requirement from the ABS that the tester demonstrate that he or she can make a deferentially hardened blade that can bend 90° without total failure. Is that better than a fully hardened blade that you can drive into a tree and hang a deer carcass from? I don't know. Is there a purpose for a deferentially hardened blade? Katanas seem to benefit from the soft spine created with deferential hardening and[/i[ putting unhardenable steel in the spine which was also done in European swords. However there is a big difference between a sword blade and a 10" camp knife blade and more so with a 4" EDC.

Doug
 
I think full and differential hardening have their place. Different designs benefit from either of the methods. One isn't correct and the other wrong.
 
Smallshop said:
Is this because edge quenching is a bit of a compromise (made for aesthetic purposes) from an ideal heat treat?
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This will fling open a can of worms (in a good way) many will have varying opinions on this one. I like a hard edge and soft spine because it holds up to MY testing. I do 95% of my quenches with furnace cement regardless of wether or not I intend to polish out the hamon. That is MY process, there are many others. In a non-kitchen accident I bent one of my 1/16 TH inch kitchen knives about 30 degrees. If that entire knife was as hard as the edge is then the knife would have snapped like a tooth pick. Because it is not, I straightened the knife and still use it.
 
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I'm still naïve to technique. I can go by what I read in one book and get excited...then find another source of info and try that instead.

I have Goddard's two books and thought it was easier to learn.
 
I got the differential hardening concept from Goddard's books. And he mentions it was easier for his students to learn. And come to think of it, another knife-maker who helped me build my forge and gave me some steel to start with recommended an edge quench, too. He is the one who also referred me to those two books. I thought I was going to make a strong knife with a process not too difficult to learn. It kind of surprised me an ABS teacher who takes heat treating to the next level frowns on that method. But I respect Kevin's opinion and will experiment with both methods. Add that to my "knifemaking to-do list."

I broke the tip off before tempering and it's hard to tell if I got silky grain or not. It seems the spine has coarse grain and the edge has finer grain.

Does that resonate with anyone? Should I still expect fine grain throughout the whole piece of steel on an edge quench?
 
Chris Railey said:
Just do not put it too close to the edge I have noticed the “softer” area as designated by an acid etch will extend a little past the actual “line” you make with the furnace cement. Also, how are you heat treating? Kiln, torch, forge etc?
Click to expand...

Thanks Chris I will watch that. These other trial knives I got are only about 3/4 wide. I was also thinking about an etch to see where things hardened. Thanks for confirming that.
I'm away from home and out of gas so I used wood charcoal from a fire I had outside the previous day. These are thin and warped in the gas forge so I wanted to try charcoal. They warped some, but not as bad. It was a windy morning and took advantage of that got out there before the sun was too bright. These knives were ground too thin near the ricasso. I think that contributed to them cooling too fast.

Thanks for the help. I appreciate being able to bounce my experience off other makers.
 
For thinner stock, less than 1/8 thick I grind post HT. Basically I profile, add my cement, quench then grind. It will help with warps on thinner stock. You easily could have overheated your tip during your HT espically if you were dealing with thin stock from the beginning. Did you run temper cycles before the tip broke off? Any chance of re-grinding the tip and saving the knife? if not then look on the bright side...you got the steel to harden and that is a step in the right direction.
 
Smallshop said:
Is this because edge quenching is a bit of a compromise (made for aesthetic purposes) from an ideal heat treat?
Click to expand...

Edge quenching is a compromise of a compromise, with not even much to gain in aesthetics, at least with clay you do get the aesthetics, but you can also get the advantage of a proper quench. I have differentially hardened about 2 of my own blades in the last 15 years, they were done with clay and for the aesthetic effect alone. By definition ductility is the opposite of strength and differential hardening leaves the majority of the blade ductile. I make all my ABS Intro students make two test blades, one differentially hardened, then other fully quenched and differentially tempered, quite often the differentially tempered blades pass the test much better in all aspects. Although I have also differentially tempered only two of my own blades in the last 20 years, I just like strength in my blades.

Doug Lester said:
… Is there a purpose for a deferentially hardened blade? Katanas seem to benefit from the soft spine created with deferential hardening and[/i[ putting unhardenable steel in the spine which was also done in European swords. However there is a big difference between a sword blade and a 10" camp knife blade and more so with a 4" EDC.
Doug
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Old swords are different in many ways but most significant, for this topic, is that they were made from entirely different materials than what we use today. Tamahagane and other pre-alloy direct reduction process steel had virtually no impact toughness compared to modern alloys. They could be made a little better by very careful forging and consolidation processes, but it still needed clever workarounds to these inherent weaknesses. Adding ductility from low-carbon or differentially hardened zones did keep blades from breaking but there was a compromise. If you get the spine at all out of line with the edge in a forceful katana cut you are probably going to bend the sword, the same was true of very early western swords. A little later the flexibility (the ability to spring and come back to true) became more prized, at least in the west, and you didn’t see as much ductility.

This is a very deep and complex topic, that involves many material science and physical properties, and is widely misunderstood in the blade making community. And this is why Tim Zowada and I felt it was time for another “Bending, flexing and breaking of steel” demonstration/lecture at Ashokan this year. The reason I decided to post this second reply is that I am in the process of compiling all my notes and so it was very much on my mind, since I will be explaining it all, in-depth, to the Ashokan crowd in less than two weeks.

Join us there if you want to see it all discussed and demonstrated in full, along with a ton of other demonstrations on bladesmithing.

Ashokan Bladesmithing Seminar
 
Chris Railey said:
In a non-kitchen accident I bent one of my 1/16 TH inch kitchen knives about 30 degrees. If that entire knife was as hard as the edge is then the knife would have snapped like a tooth pick. Because it is not, I straightened the knife and still use it.
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the ability to flex is geometry not HT
 
scott.livesey said:
the ability to flex is geometry not HT
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I will have to ask you to explain this one further Scott. If you heat a piece of 1095 to non magnetic and quench it in water then bend it, it will snap no matter the geometry. One reason we draw hardness from steel to keep it from breaking under stress.
 
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i have two blades, same HT, cut from same larger piece of steel. one has distal taper the other doesn't. i can flex the distal taper blade 20* to 30* using my thumb. the other blade will not flex. both blades are at RC62-63 from edge to spine.
 
In that respect I can see a distal taper being a factor however the HT does play a role in the failure point of the steel as in my example above. To say it does not would be to say annealed steel and fully hardened steel of the same type will break at the same point and posses the same qualities. If that were true why HT at all.
 
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