Case-hard steel

Shorttime

Shorttime

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Oct 16, 2011
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Hello all.

Time spent in the General forum has led me to believe that the next step for me is to build my own folding knife.

Yeah, I know, but to me, it's a more justifiable kind of crazy than spending five hundred dollars on somebody else's work. This way, I won't be afraid to carry and use the finished product.

I have a couple of questions, and I thought I would stick with what works: ask them on BF.

I want to case-harden the liners, and I need to know if there are steels that case harden better than others. A naive question, maybe, but the possibility of stress fractures at the hardness boundary worries me.

It need not be stainless, because I want to give the liners, and some of the other hardware, a black coating.

Is DLC the most wear resistant way to coat steel? If yes, then who can do it? Will it affect the heat treatment process that has gone before?

Is there a more wear (abrasion) resistant method of changing the color of steel? If so, what is it, and who should I talk to?

That's all for now. Thanks in advance.
 
I can't think of any good reason to case harden the liners. Just fully harden them and temper to the desired hardness.
 
Well...

My intention is to make a folder that is as abuse-resistant as possible. The harder outer layer would provide wear resistance, and the softer inner core would (in theory) make the liners more resistant to breakage during shock loading, such as being dropped, or being hit with some other object.

Steels, especially stainless, can get brittle as they achieve full hardness. So the goal of case-hardening is to get the best combination of mechanical properties.

I am open to other ideas, of course. Since I intend to coat the liners, I have lots of choices.

Are there steels which maintain a good combination of wear resistance and toughness with a through-hardening?
 
I may have missed this but you just said a folding knife with liners, are you making a lock-back, slip joint , liner-lock, or frame -lock ?
If it's your first, you might want to try a friction folder. Why such huge concern over the liner material ? Ti is pretty much the standard....no need for coating.
Also .....that 500.00 + price tag by most makers is well earned, and is the reason you shouldn't be afraid to carry and use it.
I would be happy to help you in any way.
 
It will be a lock-back. I'm basing it on a mass-produced design which has eighty-five percent of the features I want. My motivation for this is that I can see ways in which it could be improved.

The huge concern over the liners is because they will have loading forces transferred to them through the knife blade.

If you think I'm being picky now, wait until I start asking questions about fasteners!
 
I fail to see how the liners would take any real "load".

As far as soft vs hard steel. Martensite is far stronger than pearlite. A fully hardened liner that is tempered in the 49-52 range would be far stronger than a case hardened piece of soft steel. Take a look at the tools and fixtures that people depend their lives on....caribiners, safety hooks, escape tools, etc.........see any that are case hardened?

As far as it being necessary, have the ones in the production model had catastrophic failures in the liners? ...... actually, I never heard of a liner failure. Back springs, lock bars, inner springs, pivots, stop pins, yes - but liners, no.
 
So most any tool steel or stainless will do for the liners.

No, you're right, Bladesmith: it's not necessary. But then, there are perfectly good factory knives, so why build your own?

Because you want to. Or see something you believe can be done differently, or better. Or because it's not just about making "another" knife, it's about the skills and experience you gain along the way. Or some combination of these things. Choose your own reason.

I've decided to build my own folder for a variety of reasons. I've never found a folding knife which is quite right for me. A custom would be the logical answer, except that I would be uncomfortable using a knife that I paid five hundred dollars for, and most customs are right about that price. I would be uncomfortable using a knife I had paid two hundred dollars for..

While building my own may turn out to be less cost-effective than paying somebody else to do it, the process of building one cannot be valued with money. For example, I've already learned that there is no reason to case-harden liner slabs. I wondered why nobody had done it, since it would seem to give a good combination of mechanical properties. But apparently, there are no significant benefits over through-hardening.

As far as the other parts, my plan is to use 7/32 stock if I can get it, or 1/4". I know this will make for quite a large, heavy knife, but I'm willing to accept that. I may be overcompensating for other perceived inadequacies, but this isn't the place for that discussion :D
 
I haven't seen any indication of what this knife will be used for. Is it just to be an EDC, or is there some special usage planned?
 
What will it be used for? Oh, the usual EDC stuff: chopping down trees, splitting cinder blocks, and the occasional vehicle extrication. Once you cut the A and B pillars, you can peel the sucker like a giant Spam can!

As far as how many lockbacks I've made, this will the first. My first folding knife of any kind, in fact.

I accept that the learning curve is going to be almost vertical. I'm too ADD to go the sensible route. I simply have no interest in starting slow, with a friction folder, then moving to slipjoints, then to a lockback. So you can give me all the sensible advice you want, and I will admit to you that it is very smart and sensible advice. But that doesn't mean I'm going to follow it....
 
I don't believe that there's a problem with you wanting to start near the top and work from there but I see where your lack of knowledge on this is causing you to refuse the answers from those that do know. I could have said your ignorance is getting in the way, but since you say you are prepared to work through it all, them why bother asking here. You don't get any better responses than from Tracy and any other experienced makers will repeat the same. If you are looking for the beautiful case hardening colours useing titanium with a multi time anodizing to get the colours is another way to go. I have respect for what you want to do and wish you success, but your asking for help and then refusing it isn't the way to go, in my opinion. Just work it out on your own, test, discover, and then pass along what is found, and they will be the answers you are now being given. Frank
 
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Ouch.

All right, this is me with my foot in my mouth, as usual.

Text just doesn't have the ability to convey the same subtleties of emotion that face-to-face conversation does.

I know I'm being, well, thick, about this. And I guess I come across as a jackass at times, because it's hard to tell that I'm laughing at myself as I'm writing. Mostly because I'm pretty sure that I'm making things harder for myself.

If you folks would allow me, I'd like to take a Mulligan.

Hello All.

Time spent in the General forum has convinced me that I should move away from collecting folding knives, and into making my own.

The problem is, I like to make things hard for myself. Instead of starting with a sensible approach, such as a kit, to get myself familiar with the relationship between blade position, pivot location, and lock, I want to jump right in to making my own lockback.

I like some aspects of the Cold Steel Recon series. But I feel that some things could be improved, chiefly by the use of thicker pieces for blade, and liners. I would also like to make the lockbar thicker, but that is implied by making the blade thicker, I suppose.

I contacted Andrew Demko, and told him my plans. I'm not doing this so I can sell or copy the design for anyone else, and with that in mind, he wished me luck and said he was looking forward to seeing the result, although he was careful to point out that Cold Steel is responsible for policing copyright infringement.

I'm a little concerned about straying into a legal gray area, but that's probably a topic for another forum.

I know I would be setting myself up for disaster if I were to try building a folding knife from scratch. The relationship between the pieces is a complex thing, and takes experience to understand. Part of the rationale behind using an existing design as a starting point is to make the learning curve less steep: I don't need to try to get the lock, pivot, and blade right, because it has been done for me.

I could ask Mr. Demko to make a custom to my specifications. But, no matter how much confidence I have in his skills and abilities, the price of his customs takes them out of the range of a useful and well made tool, and into the category of an investment, that I would not be able to bring myself to use. Building my own removes that mental barrier, somehow.

There is no need for me to carry a folder which has been deliberately constructed for as much strength as possible. All of my cutting chores could be easily accomplished by many liner locks already on the market.

This isn't really about need. It's, at the risk of sounding silly, a sort of personal quest.

Accepting that I am trying to do things the hard way, I have a few specific questions I would like to ask of other makers.

Bladesmith has told me that there is no need to case-harden the liners. My other questions concern the fasteners, and a way to coat some of the hardware.

I know that there are different grades of fasteners out there, and I have seen charts that list their tensile strengths. But those numbers don't really mean anything to me. Can somebody explain those numbers in a way that will allow me to make useful comparisons between them?

Also, I would like to coat some of the hardware black, for contrast with the planned yellow G-10 handle scales. I've heard that DLC is a long-lasting way to color and protect metals, but that's about all I know about it. I would appreciate more information.

Thanks.
 
Like others have said, it's not about something (like case hardening) not being "necessary" (as if case hardening liners would be desirable, but too much trouble for most people).
It's about it not being OPTIMAL.

If you're interested in the strongest, toughest frame/structure for a folding knife, it will not include case hardening steel liners.
You want through-hardened steel tempered to a hard-spring (I agree with Stacy, it's probably about 50RC +/- 2) in carbon steel, for example.
Case hardened steel liners will simply not be as strong/durable/resistant to abuse, etc. as, say, a carbon steel through-hardened as described.

The ONLY reason I can think of to case harden liners is if you were doing color-case hardening. It could look pretty cool--but this is an aesthetic consideration alone, IMO.
 
I'll post one last commentary and then leave you to your own on this:

Just because the wheel has been round for ...oh, about 10,000 years....that doesn't mean it is the best shape for wheels - does it?
Well, maybe it does.

Just because a factory makes 10,000 knives, and has designers and knifemakers who develop those designs, and professional heat treaters who harden the parts, and metallurgists who pick the steel... that doesn't mean they have worked out the best design - does it?
Well, maybe it does.

Start by making a basic folder, or a lock back if you are ambitious. Stick with the known and accepted thicknesses, materials, and methods. These are all available through forums like this one, and the excellent books on building folders. If you insist on going off on your own, you will be a blind man leading himself through a strange woods. With no experience, you won't know what is a good direction to go and what isn't.

Some of the best folder makers around will give you suggestions and advice if you ask ( and are willing to accept it). If you don't seem to want it, they most likely will not offer it. If you want to tell them why they are wrong and you are right, they won't reply again no mater how much you want assistance.

Final note:
I personally feel that flippant or make believe profile information is for kids playing wanabee knifemaker. If you are a real person who wants to be a real knifemaker, you may want to edit your profile with real info. Age, location ( a real place), hobbies, occupation. Otherwise, you may not be taken seriously by some folks.
 
I am back. I want to suggest a starting place. It is here, as you picked to come to. If you have not, read all of the stickies and any other information, like great info from the Count if he sends you his list of helpful stuff . Now, use the search key and read and see there how a lock back is made. Once you get started is the time to ask the questions if it wasn't in the stickies and again after using the search button. You will have by then, figured materials, sizes, and of course have a working pattern which will all help and allow you to continue. One of the many things to help you along will be the tools and quality of. Will you have the use of a 2 X 72 belt grinder, drill press and a surface grinder? Concider how you will get along without them. With respect. Frank
 
I have a TON of respect for the likes of Stacy and Frank. I am sure they are not trying to "bust your B*!!$"

I think the comments were meant to steer you in the right direction. There are makers that have been making fixed blades for years that find it difficult to just jump into making a folder. It is a VERY ambitious project. Even copying an existing design will not be easy at all. It may give you a starting point but nothing more. There is still a TON of fine working and detail that needs to go into making all the parts work together even when copying. The idea is to get familiar with the processes that others have proven that work and THEN adapt your own style.

You may be self proclaimed "making things hard" and "jumping in" with both feet and not looking back but that may not be the correct or advised way. There have been quite a few people recently that have had a similar attitude and it may be perceived as an arrogant stance. The makers that sell the $500 knives have years upon years learning and refining their skills. Now don't get me wrong, I understand the gratification of making the knife yourself. After all, isn't that why we are all here? Jumping in and expecting to make a functional first folder is the small exception, not the rule.

Keep your enthusiasm, keep your drive, soak up EVERY bit of info that the experienced makers provide so you don't have to make the mistakes they have in the past.

I understand the cost/justifiability thing too. Why buy a really expensive knife when I could make it myself? Well I now have over $3500 setting up a shop and with how many knives I have finished I am right at that $500 per knife level but they are nowhere as nice as those by good makers. I do how ever get an enormous enjoyment from it which is what I think you are getting at.

As for your proposed knife, I think having a huge, thick, nearly indestructible functioning EDC would be awesome. As you stated you don't really need one, you want one. I would love to see how it turns out.

Best of luck,
Nathan
 
At this stage it might be a good idea to ask questions like "what minimum shop tools do I need to make a knife" or, "where can I send a blade that I have ground to get a good heat treatment." On second thought, searching and reading first to find that stuff out is a better idea.

Or, if your profile location was somewhere non-fictitious, there may be the outside chance that a folder maker on BF lives within 200 miles of you and would be willing to help...

Good luck, at any rate. If I see you asking any questions that fall inside my knowledge, I'll try to help.
 
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