440c and n690 co the same steel?

Gator97 said:
Spyder, how do you sharpen them? And what is the final grit you use?
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I dunno. Spyderco brown ceramic stone, or 400 grit sandpaper on a piece of leather. Depending on which knife I'm sharpening.

I should add, the only reason that I say that I would NOT use N690 for a chopper is because of its seeming similarity to 440C, which I do NOT believe is a good steel for a chopper. I do not have personal experience with N690 in a chopper.
 
Jerry Hossom said:
I've not heard of this happening, and I'd be interested to read about how it happened and what was being cut at the time. Do you have a link to a review that discusses this?
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I believe one claim was on YouTube and another was here on Bladeforums. I will do my best to track them down tomorrow.

Jerry Hossom said:
All the Spyderco knives I designed use a heavy convex edge made expressly for chopping. The edge is thick at the top of the convex, ~0.040-0,050", and would take considerable lateral force on a hard object (not wood) to chip or crack...
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Yeah, that thick, heavy convex is very reassuring, but it is the recurve lines it runs along that scared me off for good (in addition to the reports I mentioned). The prospect of having to sharpen it was daunting. While I have your attention, Jerry, how would you recommend the average knife nut approach sharpening such a long, recurved, heavily convexed blade? That Forager was so friggin' gorgeous and felt like heaven in hand that I would re-purchase it in a nanosecond with a definitive sharpening attack plan and your personal word backing up the steel's performance. Thanks for chiming in.:)
 
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That makes sense... something narrow enough to handle the inside of the curves, and one could cut the strop as narrow as necessary to handle whatever recurve needs to be tackled, also charge it with larger/higher micron diamond paste to actually sharpen if necessary rather than just polish/refine. Nice one.:thumbup:
 
I use both carbon and stainless steels but for larger blades and hard use knives, carbon I think should be preferred

i like s30vv and 154 for folders or utility blades but i you don't care about stain resistance carbon steels "should" be either preferred or taken into consideration

carbon steels can be easily sharpened even with basic tools, stainless is harder to sharpen without the proper equipment

i tend to use (not abuse, almost never abused) my knives and the things mentioned above are important to me
my 2 cents :thumbup:
Maxx
 
How do you sharpen a Kukhri?

There are several answers to this though it's not on topic. I'll mention them then move on. The easiest and best is a small belt sander (about $100 for the machine and all the belts). A ceramic rod does a fine job of touching up the edge, especially in the field. But the easiest answer of all is to simply ignore the area in the recurve at the rear of the edge. You don't use it for chopping anyway. A recurve is designed to give you the longest possible curved edge because that curvature increases the edge's penetration into whatever you're cutting or chopping.

I'd like to point out that the Blade Magazine Spring Special issue reviewed the N690Co Forester along with a number of other knives, evaluating them for a number of tasks and attributes including chopping. Admittedly, the other knives were a lot cheaper than the Forester and all of tool steel IIRC. Of a possible 5 points for each task the Forester scored all 5's except on one, Sharpening. All of the other blades scored 4 or less on everything. Forester scored a 0 on Sharpening - it didn't need to be resharpened after all the cutting and chopping it had done. If they had substituted Edge Retention for Sharpeing, the Forester would have scored 5 on that as well.

People make a lot of negative remarks about stainless steels and in some cases they should, but there is a tendancy to forget that the high carbide content in stainless steels, the very attribute that makes stainless steels hard to sharpen, are the same carbides that make the edge wear resistant.

Here's where stainless gets and sometimes deserves a bad rap. If you are heat treating a batch of 1000 stainless blades it is VERY difficult to get them all the same. The quenching rate can vary depending on where a blade is located when they purge the oven and hit it with cold air. There is a large thermal mass in 1000 blades and it can take awhile to draw off the heat and cool ALL the blades to where austenite (bad) is converted to martensite (good) - ~1000F. A blade that cools more slowly will have a higher level of retained austenite and thus be softer than blades that are quenched quickly. It will also have a coarser grain structure. So, if your blade is in the middle of the rack, it will take longer to cool than one that is nearer the cold air source and not completely surrounded by 999 other hot blades. How much variation is there? I don't know, but common sense argues there is some. I think that's why you often read of someone who has had lousy experience with a particular knife while others think it's great. When it was first introduced S30V was almost impossible for knife companies to heat treat correctly because it demands that Ms Start be achieved in under a minute or the steel will be soft and maybe brittle (I'm guessing on the brittle part, but that's the only explanation I can come up with for why some folks have seen brittleness in S30V, whereas others can demonstrate its inherent toughness). Knife companies eventually learned how to do it (I suspect it was smaller batches) and S30V blades made today are generally quite good. There are other parts of heat treating and knife/edge design that contribute to an edge being strong or weak, but the fault is not the steel. It's what is done to the steel that determines if it will perform well or not. N690Co performed better than I expected, and I'm pleased to have my name associated with it. The Cobalt seems to be doing it's job of detering cracks and that tiny bit of Vanadium does its job of refining the grain structure. Add to that the fact that Boehler doesn't put its name and reputation on the line with a steel that won't do the job for which it's intended.

So why does some N690Co not perform well? See above. Why the mixed reviews of S30V? See above. How does stainless steel make a knife blade that you can carry with confidence OR not? See above. You can't generalize about steels until you've tested it knowing that it has been correctly heat treated and the edge is specifically designed to match that steel to the application(s) intended for it. And on your end, don't baton a whittler through a piece of hickory. :)
 
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Thanks for taking time to discuss this.
I understand the comments about variability in heat treating. and I agree with your comments on sharpening vs edge retention. But even with the cobalt, is a 1% carbon stainless steel really optimum for chopping? Cutting? yes. Chopping? I'd have thought not. Honest question. But I'm not a knifemaker and I don't have your experience.
 
The short answer is no, CPM-3V is, but there are advantages to "stainless" that might make that attribute as well as decent edge retention important enough to be willing to compromise on others. The important thing is that the edge shouldn't break, and it won't if the "see above" issues are addressed properly.

I should point out too that there is nothing sacred about tool steels. If they are not heat treated and shaped properly they also have the capacity to fail, especially in the tendancy to become dull quickly. Tool steel in a wet sheath is very likely to turn a knife into useless rust in a matter of days. That's one reason special operations military usually favor stainless despite its faults, real and imagined".

Here's a comparative example of what I mean. I am often asked to re-edge Ontario machetes to turn them into one of the finest choppers I and others have ever used. Done properly, an Ontario can slice through sapplings and chop wood all day long, never chip once and still be surprising sharp when you're done. They are amazing tools. On the other hand I've never been able to cut a nail with an Ontario no matter what edge I put on it. I do that all the time with stainless to impress upon folks the importance of edge geometry with any steel.
 
Thank you! Much food for thought.

So many folks focus on how thin an edge they can put on a blade. Great for skinning game. Good for cardboard. Maybe not so good for other things. I tend to favor a more oblique edge angle on my pocket knives because I often have to cut things that don't allow me a 90° angle of attack, so there is a side vector to the forces on the blade. Thicker edges help prevent the edge bending over. I'd never considered the possible effect on chopping performance. I'll have to cogitate on that and see what sorts of projects I can come up and see if I can get a feel for it.

Thank you, sir.
 
Always good when you get 'the man' on a thread and explaining some specifics of steel. Thank you, Jerry, for an excellent and very informative post. Actually, I mean, several of them. :thumbup:
 
Jerry,
I just wanted to chime in and tell everyone that i own a Hossom Forester and it is great. Chopps like nobody's business and so far no edge damage. Not to mention the knife is deceivingly light. Well done sir.
Jon
 
I've chopped with both N690Co (a Spyderco Hossom) and 440C and they've both held up fine. They're both medium-toughness stainless steels. They are tougher than 154CM but not as tough as AUS-8 or 13C26 or H1.
 
I purchased two Forresters both because of Jerry's reputation and Syderco's willingness to market them. As I began to read through this thread I thought that I made a big mistake but I feel much better now. I too felt I was taking a chance on this steel and felt that 1095 would be a better choice but I am not a knifemaker just a user and am influenced by opinion. I like to think I have a good idea of what I want and try to make sense of all the info and hype but admit that sometimes when I make a purchase feel a little uncomfortable.

Thanks Jerry I feel much better and feel preety good about my purchases.
 
440B is more appropriate for a chopper than 440C. My 440B kukri works fine.
 
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