An Existential Hardness Question

Larger carbides are not necessary a bad thing like folks were saying 10 years ago. They can help make the edge more aggressive with slicing/drawing the edge when sharpened properly.I the matrix is harder +60rc it holds the Carbides better

So,from all of the above i gather that indeed the following is axiomatic-
The thing to keep in perspective is that an Rc 55 knife will cut just as well as an Rc65 blade. The difference is in two main areas - Edge life, and edge durability. At Rc 65, the edge will not wear down and get dull as fast as the Rc55 edge, but it will chip much easier.
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and that nowadays the Only difference between the older carbon alloys and these modern super-hard ones is the complexity of maintenance?

I enjoyed watching the video DeadboxHero posted,thank you for that.
The flexing of the tip in the beginning is Very impressive.
However,the overall geometry of the knife shown is considerably more conservative than an average processing knife...Would a similar alloy at ditto HT be capable of sustaining a much thinner,keener convergence angle blade?
Many knives that i use are around 1/8" on the spine with straight bevels extending over 2" when new...(and from factory need to be immediately re-profiled to a much keener secondary bevel..).

I do apologise if i'm diluting this topic,Cushing H.,as well as for possibly being somewhat daft...It ain't easy to crunch all such data,for a layman...:(
 
I send a strop, and compound with each kitchen knife. I do free sharpening, but with cross border shipping, most don’t take me up on it.

I have two stops, one (a wheel) on the Tormek, and another a belt on my 1x30 sander (I really need to get a 2x72 leather belt for my grinder. You are right though - it might well be worth making a small board mounted strop to keep in the kitchen. Thank you for the idea!

I also offer to sharpen for those I have given knives to - but most seem to not want that. My son in Atlanta, who is about to unwrap this knife (AEBL, 62 rockwell)...
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has categorically refused to send his other knives to me to sharpen (even though he freely admits they are totally shot as far as their edges go). go figure......
 
nowadays the Only difference between the older carbon alloys and these modern super-hard ones is the complexity of maintenance?
Jake - no problem for your comments - they have been helpful! Re. the quote above - that is essentially the point I was looking for input on - though Stacy said it so much more clearly :-)

back in the late 70's when I first started working with knives, the choice was basically between the high-carbon of the time (not even sure of the actual alloy) and the stainless of the time - which were much harder to sharpen on a stone - but the softer high carbons would sharpen pretty easily. Given currently available sharpening technology, those softer high carbon steels sharpen even more easily! Yes, the tradeoff is that that edge just does not last as long. I know there are people here who will (have) just said "higher rockwell is better" ... but I view it as just that - a trade off (again, Stacy said that very well). It is not that absolute though: too soft and you just can not form a real edge (I am not sure where that boundary is though - maybe per what stacy said somewhere around 50 rockwell?). I have a knife that is about 100 years old (from my grandmother) that is clearly very low hardness, and though I have tried, I just can not get that thing sharp (or at least just can not raise a burr - the edge just bends).

Both DeadboxHero and Willie71 are right though - I should give a ceramic rod (and small strop) sitting in the kitchen a try: they might very well give me that "30 seconds and you are back in business" capability (Ive been meaning to get a ceramic rod for a while - just been putting it off.....). Of course one alternative is - more knives in the drawer !!! :-)
 
Warren - I know, I know, I know. But that takes us back to a point that has caused many "heated discussions" here in the past: do you/we/I always take the "absolute best" approach - or do we take an approach that might be easier/faster and accept the tradeoff. When I look at the data posted by Larrin there is definitely evidence that the performance of the edge coming off a grinder is degraded - but I would not say it is "ruined". For a short while I tried sharpening on a (non speed controlled) HF 1x30 sander - and that clearly damaged the edge to an unacceptable degree. Coming off the 2x72 grinder on very slow speed I (for my own purposes) am ok with the sharpness and performance of the edge (same for the knives I am giving to friends and family, all of whom dont really care that much about edge performance.

Now ... if I was selling a knife like you and others are for mega bucks to professionals who really understand what edge performance is - I would either use the Tormek followed by waterstone, or use a diamond stone.....
 
Sounds like you just need a good 10-12" ceramic honing "steel" instead of the grooved one. It will easily take care of bringing back an edge in 15 secs. I've used it on m4 and 4v at 67rc with zero issues.
 
Sounds like you just need a good 10-12" ceramic honing "steel" instead of the grooved one.
agreed. Like I said, I have just been lazy in obtaining one :-( . No way I would let that grooved metal steel anywhere near my more recent (modern alloy, harder rockwell) blades!
 
I buy 3/8" and/or 1/2" by 8.5" long ceramic kiln rods in bulk and turn handles for them on the lathe. The rods cost around $2 each in 5 and 10 packs (ebay and Amazon). Glue one in the hole and you have a great ceramic strop rod for less that $5. They don't sharpen a dull knife, but will restore an edge in a few passes if the edge is still servicable. They can be made even cheaper with the shorter 4.5" sticks. Make some and give them away with a high end knife.

As to the "High Carbon" steel of the 70's. It was simple carbon steel with 1.00% carbon. 1095 and W1/W2 mostly. Some had a little chromium, similar to 52100. Not much changed in cooking knives from 1940 to 1990. Todays stel has much higher alloying. Some modern stainless has 30% alloy content. Even carbon steels can be 10% alloying. The recent additions of larger amounts W, V, Nb/Cb, Co, and N have change steel a lot. Before that is was mainly Cr and Ni, with small amounts of W sometimes.
 
Biggest thing needed imho is proper geometry... If you have a knife with a thick grind, thick edge, and obtuse angles then no - a steel won't get it back to shaving sharp. But if you have everything nice and thin, and touch up just the apex on the honing rod it's a cinch and very quick. Even a full sharpening on diamond stones is quick when the edge is only .005-.010" bte at 10-15 dps
 
Warren - I know, I know, I know. But that takes us back to a point that has caused many "heated discussions" here in the past: do you/we/I always take the "absolute best" approach - or do we take an approach that might be easier/faster and accept the tradeoff. When I look at the data posted by Larrin there is definitely evidence that the performance of the edge coming off a grinder is degraded - but I would not say it is "ruined". For a short while I tried sharpening on a (non speed controlled) HF 1x30 sander - and that clearly damaged the edge to an unacceptable degree. Coming off the 2x72 grinder on very slow speed I (for my own purposes) am ok with the sharpness and performance of the edge (same for the knives I am giving to friends and family, all of whom dont really care that much about edge performance.

Now ... if I was selling a knife like you and others are for mega bucks to professionals who really understand what edge performance is - I would either use the Tormek followed by waterstone, or use a diamond stone.....

I’m an intermediate maker, not an expert. Still, $400.00 is an investment for most people for a good kitchen knife.

I use a 220x diamond plate to get the initial edge bevel. This just takes a couple of minutes, even with z-wear or s35vn. A good diamond plate costs more than a 1x30 though....

As custom makers, we cannot compete price wise with mass produced knives, so we offer the absolute best performance we can, but that equation includes ease of sharpening. Anyone can touch up AEB-l, or 15n20 at Rc62. No need to go any lower than that. You give up fine edge stability if you go softer, requiring thicker edges.
 
I buy 3/8" and/or 1/2" by 8.5" long ceramic kiln rods in bulk and turn handles for them on the lathe.
Stacy - that is an incredible idea! Thanks. (dont have a lathe - but can roughly round material on my grinder - I have lots of black wallnut blocks). I might just try sending one of these to that recalcitrant son of mine in Atlanta! :-)
 
I use a 220x diamond plate to get the initial edge bevel. This just takes a couple of minutes, even with z-wear or s35vn.
You know - this brings up maybe an important question: maybe something like 20 years ago I tried diamond "stones" - gave up on them because they wore out too darned fast (and so I have not even considered them since). Are the "modern" diamond blocks more robust (and thus worth the cost) than those that were made 20 odd years ago?
 
Biggest thing needed imho is proper geometry... If you have a knife with a thick grind, thick edge, and obtuse angles then no - a steel won't get it back to shaving sharp. But if you have everything nice and thin, and touch up just the apex on the honing rod it's a cinch and very quick
Josh - absolutely agreed. But let me try to highlight/clarify the difference between that perspective (which is that of a "maker") as opposed to my perspective as a "user". Take the knife below:
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This is a vintage 1980 Sabatier "carbon" 5 1/2" chefs knife. When new, the heel of the edge ran right up to the lower end of the bolster. Over the years, it has been sharpened many, many times, and the edge has withdrawn considerably upward (making that bolster something that is just in the way, and also increasing the BTE thickness). I try to keep the edge angle at 15 degrees per side and limit material loss .... but that has its limit, and the years have taken their toll on the BTE thickness. I do not recall the exact measurement - but I can tell just by feel that the BTE measurement is .... Not Good. :-) . With the softer steel, I can somewhat reasonably keep this knife going (it is my go-to knife for taking pits out of avocados :-) ). I think ANY knife, however good the initial edge geometry, would suffer this kind of degredation over the years (20 - 30 - 40 of those years). It is from that perspective that I still sometimes think that the softer steels are more "friendly" when it comes to making major "renovations" in the blade geometry over the years. Also take for example that original chinese peasants cleaver: I completely re-profiled and convexed the edge and got quite a good working edge on it - and it took me maybe 20 minutes.......

(BTW - I am working with JT to try to get to him profiles of the older Sabatier knives I have. I actually really hope I get a chance to work up a version of this blade (in 15n20 maybe ??) at rockwell 62 or 64 (without the full height bolster!), and see how it performs with an edge geometry as you describe..... :-) )
 

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Since such traditional N.European forms came up i'd like to in the interest of fairness note that it's possible that they kept their tools at a given hardness quite deliberately...
Conservatism,natural to all times and trades,is quite likely as cause,but i doubt Very much it was strictly technical,as in inability to achieve Nth geometry at a given hardness due to lack of metallurgical know-how...

Obviously,even long before (deliberate)alloying the art of thermocycling plain C steel was perfected.Filemaking,among other trades,many other examples of finesse in dialing up and utilising a quite high degree of hardness.

An example that comes to mind is that old European custom of chopping meat,especially the bones.(It Wasn't because they didn't have saws!:),but for a number of valid culinary reasons).
In any case,it necessitated high degree of hardness,and toughness was compensated for by means of increased convexity of edge.

Just for giggles here's a short video.Is is a promo by a smith specializing in butcher's axes` and cleavers,with a professional butcher doing the testing.The only comments the butcher makes are that "it does the job/remains sharp/needs re-dressing only once a week(of full-time work)".
(this video is Russian,but it only echoes/apes an old German/French culinary tradition;i.e. places where very high quality iron ores were located,as well as of very sophisticated early metallurgy developements).


In this video a smaller beef is processed,however these guys chopped even the very largest and hardest of beef leg bones & joints.It wasn't done directly,but at a funky oblique angle,breaking the bone by this special "shock" effect,for lack of technical term.
 
You know - this brings up maybe an important question: maybe something like 20 years ago I tried diamond "stones" - gave up on them because they wore out too darned fast (and so I have not even considered them since). Are the "modern" diamond blocks more robust (and thus worth the cost) than those that were made 20 odd years ago?

depends on the brand. I’ll take some pics of the two types I have. One is still working very well after several years, the other wore out after about 50 knives.
 
I didn't find my last kitchen blades in 26c3@63-64hrc much harden to sharpen on my Shapton stones than my 80CrV2 blades, which I do mostly in the 60-61 range. That's one thing I like about carbon steels, they're so easy to keep super sharp, even when very hard.
 
You should shape that bolster down so you can acutually make contact on the cutting board.



Josh - absolutely agreed. But let me try to highlight/clarify the difference between that perspective (which is that of a "maker") as opposed to my perspective as a "user". Take the knife below:
View attachment 1252993
This is a vintage 1980 Sabatier "carbon" 5 1/2" chefs knife. When new, the heel of the edge ran right up to the lower end of the bolster. Over the years, it has been sharpened many, many times, and the edge has withdrawn considerably upward (making that bolster something that is just in the way, and also increasing the BTE thickness). I try to keep the edge angle at 15 degrees per side and limit material loss .... but that has its limit, and the years have taken their toll on the BTE thickness. I do not recall the exact measurement - but I can tell just by feel that the BTE measurement is .... Not Good. :) . With the softer steel, I can somewhat reasonably keep this knife going (it is my go-to knife for taking pits out of avocados :) ). I think ANY knife, however good the initial edge geometry, would suffer this kind of degredation over the years (20 - 30 - 40 of those years). It is from that perspective that I still sometimes think that the softer steels are more "friendly" when it comes to making major "renovations" in the blade geometry over the years. Also take for example that original chinese peasants cleaver: I completely re-profiled and convexed the edge and got quite a good working edge on it - and it took me maybe 20 minutes.......

(BTW - I am working with JT to try to get to him profiles of the older Sabatier knives I have. I actually really hope I get a chance to work up a version of this blade (in 15n20 maybe ??) at rockwell 62 or 64 (without the full height bolster!), and see how it performs with an edge geometry as you describe..... :) )
 
I haven't read all the posts, but will offer some comments on hardness history and modern knives.

Picking the final hardness has always been a factor of available HT methods and the desired sharpenability.

Starting around 3000BC and continuing for several thousand years, knives were made of crudely smelted steel, and hardened by eye in some sort fire and in some sort of of home brew quenchant. The blades were sharpened on some sort of natural rock by hand. These blades were probably Rc 40 at the most. People considered that hard.

As time went by, steel was alloyed a bit better, rocks were hewn into grinding wheels and sharpening stones, and HT was a bit more refined. This was the norm from around 500AD to 1900AD. These blades were around Rc 45-50 at most.
People considered that hard.
It started improving during the last half of the 19th century with the advent of the Bessemer steel processes.

By 1900, steel metallurgy and manufacturing was pretty good and HT was much better understood. Alloying was still low and simple. Machinery was used to shape and grind the blades. HT was done to a max of Rc55. This would allow the user to easily sharpen the blade as it got dull. Home sharpening was still by a stone of some sort. During most of the 20th century, knives were between Rc45 and Rc55. People considered that hard.

Around 1990, with knifemaking becoming a popular hobby, and newer steels becoming available, hardness slid up to Rc 58-60 as the norm. Most everyone is very happy with this hardness range. This hardness could be easily shaped and sharpened on belt grinders with SC and AO belts and powered wet grinding wheels, and kept sharp by most users with a good Norton or other sharpening stone. To make sharpening easier, all sorts of sharpening systems and machines came out … with most ending up on shelves and in drawers. It wasn't that the Chef's Choice or Lansky couldn't sharpen a knife well … it was that they were expensive and required some skill. Good as they were, they left a poor edge more often than not and couldn't compare to a sharpening stone for ease.

With the advancements in both metallurgy and equipment of the last 20 years, Rc 63-65 blades are now possible and sharpening them can be done with our modern belts and equipment as well as diamond plates and laps. The issue is that the normal user can't maintain the edge easily. Diamond stones are available for the home user, but most people either don't use them or use them wrong. New sharpening equipment came out, some costing thousands of dollars, but it didn't change the public's desire to quickly and easily sharpen their knives.
The general public still wants a knife that is easily resharpened in the kitchen in a few minutes or less. Commercial knives, both kitchen and hunting/fishing, have barely increased in hardness since 1990. The vast majority still range between Rc55 and Rc58 . Kitchen knives have started to slide up to Rc60 only in the past few years. The trend for hobby knifemakers is to make them really hard and sharpen on their equipment. Rc 62-65 has started showing up often. You even hear about guys using special metal alloys and getting Rc67 knives. This is a good thing for the maker/user, but won't affect the public's oppinion much at all, due to the end user not being able to sharpen the knife properly himself.

The thing to keep in perspective is that an Rc 55 knife will cut just as well as an Rc65 blade. The difference is in two main areas - Edge life, and edge durability. At Rc 65, the edge will not wear down and get dull as fast as the Rc55 edge, but it will chip much easier. The Rc55 edge can be quickly sharpened as often as needed, but the Rc65 edge will have to be sharpened using special equipment and skills. Again, the general public won't want a blade that will chip easily if misued or one that they can't sharpen easily.

I agree with most everything you say except my EDC is hardened to HRC 67 and sharpens easily on Shapton Glass Stones which are Aluminum Oxide. I don’t consider Al203 stones to be special equipment. The Spyderco Sharpmaker Stones also make short work of sharpening my EDC.
 
You should shape that bolster down so you can acutually make contact on the cutting board.
That is non sequitur. I was talking about the BTE thickness. This particular knife is too small for chopping - i use it for draw slicing - so the protrusion of the bolster, by itself, is a non issue for me.
 
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