Blade Steel Rehardening

[cotdt]

If anyone is interested, I can reharden your blade for free (not including shipping). Any steel, any attainable hardness, so long as you know what steel it is. I should note that there may be some risk involved, depending on the steel and desired hardness. It's like turbocharging a car engine.

Harder steel is suited for holding a thin wicked sharp edge for a long time. You typically lose some impact toughness but gain strength and wear resistance. The Rockwell hardness scale is near-logarithmic, and each point is significant.

My purpose is to collect people's experiences on rehardened blades, especially since many of these steel/hardness variations are not on the market. Want to see what your 13C26 blade can do at 62-63 rc? Well, here's your chance to try it, while contributing to our knowledge base. By volunteering your blade, you also get to own something unique.

Each blade is heat treated individually in a precise temperature-controlled kiln. I have access to very high temperatures and cryogenic equipment to get up to the maximum hardness out of each steel. I will treat your knife professionally as if I was getting paid. You can post any questions here or send me an email.

Useful posts:

Steels I've tried:
http://www.bladeforums.com/forums/showpost.php?p=7469202&postcount=24
Gator97:
http://www.bladeforums.com/forums/showpost.php?p=7470875&postcount=34
http://www.bladeforums.com/forums/showthread.php?t=691539
Walkthrough of the process:
http://www.bladeforums.com/forums/showpost.php?p=7490573&postcount=133

 

[Bill DeShivs]

Why would a properly hardened blade need to be "rehardened?"

 

[cotdt]

Why would a properly hardened blade need to be "rehardened?"

It doesn't. Question is, what is considered "properly hardened"? Let's take an example: AUS-8A at 61 rc has edge retention comparable to more expensive steels like 154CM/S30V/VG-10, but can take a thinner, keener edge. Unfortunately most companies run AUS-8A at 56-58 rc, which forms massive burrs while sharpening and the edge holding is a fraction of what the steel is capable of. With an oil quench and cryogenic treatment as part of the quench, yes the heat treat would be more expensive and few companies oil quench anymore, but here is where more performance can be squeezed out.

Harder steels in general can take thinner, keener edges. All else equal, 3-4 points hardness increase also doubles the edge retention. Again, this is a free service for those interested.

Edit: To clarify, I'm not saying that the industry is "improperly hardening" AUS-8A. I'm saying that more performance can be gotten with a custom heat treat, at the expense of some impact toughness. I should have chosen my words more carefully.

 

[Planterz]

Question is, what is considered "properly hardened"? Let's take an example: AUS-8A at 61 rc has edge retention comparable to more expensive steels like 154CM/S30V/VG-10, but can take a thinner, keener edge. Unfortunately most companies run AUS-8A at 56-58 rc, which forms massive burrs while sharpening and the edge holding is a fraction of what the steel is capable of. With an oil quench and cryogenic treatment as part of the quench, yes the heat treat would be more expensive and few companies oil quench anymore, but here is where more performance can be squeezed out.

Dozens of well known, respected, and lauded companies use/have used AUS-8. Such as:

Spyderco
Al Mar
Benchmade
SOG
Kershaw
CRKT
Gerber
Blade-Tech
Camillus

to name a few.

And you're saying that you've discovered something that they haven't? Something that all these company's metallurgists, who have been in this business for years, haven't figured out for themselves?

Yeah, somehow I doubt that. I believe that as much as I believe the shabby bearded guy on the bus that he's got the perfect plan for universal heath care.

AUS-8 has too little carbon to be taken to 61Rc and not be extremely brittle, fragile, and weak.

Again, this is a FREE service for those interested.

And a waste of money.

 

[cotdt]

And you're saying that you've discovered something that they haven't? Something that all these company's metallurgists, who have been in this business for years, haven't figured out for themselves?

AUS-8 has too little carbon to be taken to 61Rc and not be extremely brittle, fragile, and weak.

Please point to me where I claimed to have discovered something they haven't? They heat treat AUS-8A (different from AUS-8, btw) for toughness and sharpenability, convenient as the industry moved away from oil-quenching steels and it would be too expensive to cryo treat right after the quench. AUS-8A can reach 61+ rc just fine, max hardness is 62 rc after tempering. And it's not brittle.

I'm sorry if I hit a nerve to cause you to be so angry. I am merely offering a service to my fellow steel enthusiasts, many of whom prefer hardness over impact toughness. It's all personal preference.

 

[The Government]

Could you give a ball park figure on your price for common blade steels and sizes?

I am just curious at this point, but it is nice to know that if I ever wanted to I could give my blades a custom heat treat.

Thanks

 

[cotdt]

Could you give a ball park figure on your price for common blade steels and sizes?

I am just curious at this point, but it is nice to know that if I ever wanted to I could give my blades a custom heat treat.

Thanks

It's free... =P

I just want to put my equipment to good use. Made a couple knives but haven't been using the shop lately. I can do any steel, my oven can go past 2200F and I have some liquid nitrogen for cryo.

 

[Planterz]

Please point to me where I claimed to have discovered something they haven't? They heat treat AUS-8A (different from AUS-8, btw) for toughness and sharpenability

Exactly. If AUS-8 was a superior performer at higher Rc levels, they wouldn't be using steels like S30V, D2, or ZDP-189, which aren't too brittle, they'd stick with AUS-8. They don't. For a good reason.

If some random car tinkerer came up to you offering a new miracle fuel filter that somehow improved gas mileage by 10%, and it looks like it's made from duck tape, toilet paper tubes, and cotton balls, would you believe it?

It's never been tested. No patents. No development grant. It's different than what multi-billion dollar car manufacturers and parts companies have been doing for years. But somehow this guy has made what thousands of experts and billions of dollars haven't been able to figure out themselves.

And it's FREE!

That makes it worth it, right? Or maybe it'll ruin your engine and cost you thousands in repairs.

 

[cotdt]

Exactly. If AUS-8 was a superior performer at higher Rc levels, they wouldn't be using steels like S30V, D2, or ZDP-189, which aren't too brittle, they'd stick with AUS-8. They don't. For a good reason.

Yes, the reason being cost and convenience. Higher alloyed steels can obtain full hardness with an air quench and typical triple temper at 975-1000F. In my use, steels like AEB-L and the similar AUS-8A perform better at higher hardnesses, but oil quench and cryo treatment are required. I can only talk about my own experience, but there are custom knifemakers that advocate the higher hardness levels for this steel, I would mention names if I had their permission. All else equal, lower carbon makes a tougher steel, as you would have lower carbide volume. This allows you to bring the hardness level higher w/o becoming brittle.

In CATRA tests, the steel's inherent wear resistance doesn't matter as much as blade geometry for edge retention, at least for cutting soft/medium objects. Harder steels with lower carbide volume can take and hold a thinner edge, which is the predominant determinant of edge retention, as proven by CATRA results.

 

[eyeeatingfish]

Youll have to forgive my skepticism but why would you offer such a service for free when admittedly the steel foil used to heat treat is expensive? Are you trying to gain experience?
You have no shortage of posts so I dont think you are a drive by person trying to scam us into sending you our knives.
You have to admit this all seems too good to be true.
You arent just offering free heat treating but this retreating....
So I am wondering what your motive is.

 

[Jason B.]

There are others that reharden blades too. One I remember was a forum member who had their 110v shallot taken up to 63-64 IIRC because kershaw only had it at a 58-59. Just because its a big company does not mean they will make products that are to their maxium performance levels. For example: the engine in your car only runs at 75% of its maxium output, this like a softer heat treat allows for a tougher motor that will last through years of abuse. So if you wanted to up the HP of your car would you replace the motor every time or add a turbo?

I personally think its a good option, not all ht's are equal.

 

[cotdt]

Youll have to forgive my skepticism but why would you offer such a service for free when admittedly the steel foil used to heat treat is expensive? Are you trying to gain experience?
You have no shortage of posts so I dont think you are a drive by person trying to scam us into sending you our knives.
You have to admit this all seems too good to be true.
You arent just offering free heat treating but this retreating....
So I am wondering what your motive is.

I'm interested in other peoples' experience with harder knives (like the example with AUS-8A I gave). My own experience is very good, but usage patterns differ.

The idea began when I was talking to a fellow member here, and I agreed to reharden the 1095 of his RAT Izula. He got it for cheap so he was willing to risk the knife if the rehardening process somehow doesn't work out. Now I'm interested in carrying this idea further, to other steels.

If I end up stealing the knife, I would obviously be reported and banned, as well as arrested... putting at risk my future career as a physician, exactly what I need... Besides, charging for services violates the ToS of this forum, I would have to get my own forum.

 

[Planterz]

One I remember was a forum member who had their 110v shallot taken up to 63-64 IIRC because kershaw only had it at a 58-59.

Kershaw lists their 110V Shallot at 60-62Rc. Was his improperly hardened? Am I missing something?

 

[cotdt]

Kershaw lists their 110V Shallot at 60-62Rc. Was his improperly hardened? Am I missing something?

It's not improperly hardened, but the owner wanted a higher hardness. You can ask ThomasW what was the rationale, but please do it in a new thread. ThomasW is a classy guy :thumbup:

 

[Planterz]

It's not improperly hardened, but the owner wanted a higher hardness.

I'm merely confused with the differing numbers. I understand if the owner wanted his blade harder than the 60-62Rc Kershaw hardens it according to their listed specs, but if it's supposed to be spec'd at 60-62Rc, and he tested it on his own and it was only 58-59Rc, then it does sound like it was improperly hardened. I'm not trying to be argumentative, just trying to clarify.

 

[Jason B.]

Goes back to the example of the car motor, just because they say your getting 300 hp does not mean you will get it every time. I have S30V in several knives and the HT is different for all of them, even ones from the same company.

 

[cotdt]

I'm merely confused with the differing numbers. I understand if the owner wanted his blade harder than the 60-62Rc Kershaw hardens it according to their listed specs, but if it's supposed to be spec'd at 60-62Rc, and he tested it on his own and it was only 58-59Rc, then it does sound like it was improperly hardened. I'm not trying to be argumentative, just trying to clarify.

Well in that case we can all agree it's improperly hardened. Can't expect it to meet specifications all the time. However even if it did meet specs, I think the owner wanted 64 rc anyway which is the max hardness for S110V.

 

[cotdt]

Goes back to the example of the car motor, just because they say your getting 300 hp does not mean you will get it every time. I have S30V in several knives and the HT is different for all of them, even ones from the same company.

I had the same experience with S30V, with wildly differing heat treats. The heat treating temperature really needs to be precise with this steel. S30V really likes a polished edge. I have one at 61-62 rc, it isn't chippy with a thin and polished edge.

 

[FlaMtnBkr]

I'm merely confused with the differing numbers. I understand if the owner wanted his blade harder than the 60-62Rc Kershaw hardens it according to their listed specs, but if it's supposed to be spec'd at 60-62Rc, and he tested it on his own and it was only 58-59Rc, then it does sound like it was improperly hardened. I'm not trying to be argumentative, just trying to clarify.

So your not trying to be argumentative in this post, but what about all the others in this thread? It sounds like cotdt is offering a good deal maybe because he is passionate about knives. Maybe he is like some of the other members that sharpen knives for about the cost of shipping but taking it a step further in something he has some experience with.

If you don't want your knife re-hardened that's fine but why poopoo his thread?

I don't have a dog in this fight just making an observation.

 

[Gator97]

Kershaw lists their 110V Shallot at 60-62Rc. Was his improperly hardened? Am I missing something?

Yeah, on that one you are, sadly. My 110V was 59HRC. So were two other 110Vs that I know of. One was 58HRC. I did send few blades to Phil Wilson for rehardening and regrinds. 110V is now 64HRC. Once I get it back form Tom Krein I will post updates and photos. If you are interested in details, they're here.

I don't have recent experience with Aus steels. Haven't bought any for a long time. However... Regardless of the steel used there are few obvious facts worth noting here and I am not sure what do you have to object to those.

Dozens of well known, respected, and lauded companies use/have used AUS-8. Such as:
Spyderco Al Mar Benchmade SOG Kershaw CRKT Gerber Blade-Tech Camillus

My kershaw was below the spec. Of 5 Behcnmades(2 M2 710s, 3 Nimravus blades) I've tested HRC, 3 were below 60-62 HRC, 2 at 60HRC. I have seen reports from this and other forum members about their RC tests, and at best those knives are at the lower end of the specified RC range. So far, I have yet to see a report in which the knife was tested to higher end of the spec, or above it.
I've been using rehardened 64HRC M2 since April 09 and performance difference between what it was and what it is is day and night. Twice as thin edge(20 deg total vs. 40 total before) and for the same use as before I never had to sharpen it so far with anythign coarser than 10K whetstone and 0.5mic / 0.25mic diamond charged strops.

And no, Phil Wilson didn't invent anything for M2 steel heat treatment either. As he said, he just went by the book. And came out with 64HRC blade. I strongly suspect the same book is available to all of those companies.
And I do believe Benchmade does better job than many other knife companies out there. They're still my favorite folder makers. But I'll keep rehardening whatever I can.

And you're saying that you've discovered something that they haven't? Something that all these company's metallurgists, who have been in this business for years, haven't figured out for themselves?

Unless we read different OP, he's clearly not And mass makers do have their reasons to under heat treat their knives, and when you heat treat large batches of the knives it is pretty much impossible to get even heat treatment across the batch.
To name a few would be abusive users, easier sharpening, ease of machining which translates into less wear and tear of their tools and machinery, and heat treatment to higher RC in general requires higher temperatures. Especially for modern, exotic steels like cpm 110V and ZDP-189. In other words, it is more expensive and not so sure every one of them have furnaces capable of that either, those who do would still consider the cost of increased wear of the heat treating equipment.

Besides, can you name a mass manufacturer and steel which they take to its max? Do you believe 60-62HRC is optimum for 110V in a folder knife? May be it is optimum for average user, but it can take significantly more. So does ZDP-189. So, why do you believe AUS-8 is at its best from mass makers?
You don't think they're in it for profit and cost cutting isn't in their interests? Or 52-54HRC kitchen knives that are prevalent on the mass market, that's the optimum for 440A, 440C or whatever else they use?

And a waste of money.

Again, unless we read different OP, he said free didn't he?