Rockwell Hardness

HughesTMH

HughesTMH

Joined
Mar 20, 2012
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172
Reading many a thread here I see many others are calling for CRK to increase the Rockwell Hardness on the heat treatment to help keep the blades edge a little longer.

I am not sure I understand this. If you increase the hardness, you make the blade more brittle. This increases your likelyhood to chip or microfracture the blade.

I can speak from experience, it is a lot easier to sharpen a blade than to get a chip out. When I had a chip, I have welded them back in and reground the metal but it changes the properties of the steel to make it even more brittle.

So other than keeping a blade sharp longer, please explain to me why you would want a harder steel. Also, the harder the steel, the harder to sharpen.

Any thoughts or reasoning would be appreciated.

Thanks!
 
They are willing to trade some toughness and ease of sharpening for greater abrasion resistance. You apparently are not. That's what makes the world go 'round.
 
S30V holds up to 61-62 hrc without having problems as per Crucible, where HT'ed correctly and very well
any steel has a range of working HRCs, where it can be easier to sharpen and soft to accept any use and a high hardness where it's harder to sharpen (keep in mind, not always correct with any steel) but it's more "prone" to damage
to chip a knife badly you need BAD HT and a very hard use/abuse, OK that ANY knife and steel CAN be damaged (we know it ;) )

S30V at 58-59 from CRK is very good stuff, not the same from other manufacturers, I didn't like Spyderco's HT with is the same HRC (same 58-59 from what I know)
a good HT is costly and refelcts in the knife's costs-price
kershaw and BM HT them to 59-61 or +- 60, it's very tough and holds an edge very long, takes some more effort to sharpen (not hard though) so it may not easy for everyone
Fantoni HTs them to 61-61, very tough still (well done ht) but a bit harder to maintain BUT it's not gummy at all like spyderco's, it feels cool when worked on a strop with sandpaper

so it's a matter or preference but also a matter of well done HT, not every manufacturer or maker does the same even at the same hardnesses, when you use or have used many from many manufacturers you get an idea, personal but it's an idea
D2, 1095 and most steels are the same, you can have a working low hrc one and a bad high hrc one as you can have a bad low hrc and a great high hrc, it's all a matter or knowledge, tools, carefully made job...

2 cents
Maxx
 
I currently have two sebenzas that were re-heat treated to 60 (s30 and s35) by Paul Bos HT (Farner). Gotta say it makes a huge difference, no chipping to speak of yet. Some people dig how CRK HT's their knives, I just wasn't one of them. I found the stock HT resulted in blunting, the edge would literally dent inward. Also found the edge would roll real easy as well. Many say this is preferable to chipping and sure I can understand that argument. However mine rolled faster than any knife I've had. Dulled in half the time my VG10 delica would.

At 60, both steels hold a edge great and are plenty tough for edc. Haven't had any catastrophic blunting or rolling either. Who knows, maybe I received a couple lemons as far as HT goes.... maybe not. To me, they both seemed around 57-58. I just wish CRK bumped up to 60 out of the factory. These are my favorite pocket knives, I haven't found anything that compares in F&F. However I don't buy these things to collect, I use every one. So to me, an edge that doesn't dull before a whole work day is important.
 
It's "hard" to say for me. Most of my knifes are S30V/S35VN. it's just a popular premium steel. It seems to me that they are all very similar even at different target hardnesses. My Striders, being the hardest, actually seem really simple to sharpen. The CRKs seem to really hold on to the burr, making it more difficult to remove. When I sharpen, if I'm not 100% sure I've removed the burr I push the blade into a piece of hardwood & check for folding in the edge. Cutting paper will tell you if it is sharp, but it does not mean that it has a good edge. I believe this encompasses why folks have a problem with CRK edge rolling.

Until I figured this out I greatly preferred a harder HT. Now that I know I just need to be more careful with sharpening I certainly appreciate the fact that a little lower HT will give my blade a LOT more durability.

My Shirogorov is also 58-59 HRC & it performs amazingly!
 
Yep, better chance to chip. That's why I'm one of the few calling for it to drop down to the 40s. Little chance for it to chip then.
 
kreole said:
Yep, better chance to chip. That's why I'm one of the few calling for it to drop down to the 40s. Little chance for it to chip then.
Click to expand...

Any softer than it is right now would be pretty horrible. The factory edge never chipped on me and that is 58-59. In the 40's, I think if you simply looked at the edge it would blunt.
 
SMI said:
Any softer than it is right now would be pretty horrible. The factory edge never chipped on me and that is 58-59. In the 40's, I think if you simply looked at the edge it would blunt.
Click to expand...

It was a joke friend :) to point out softer and less chipping does not automatically mean better
 
Op, metallurgy isn't as cut and dry as you make it sound.

S35VN can comfortably be ran around 61 with literally zero problems with chipping. Also, the bump from 58 to 61 wouldn't add any appreciable difference in sharpening. The composition of S35 is what makes it so easy to sharpen, not the softness. It does help, yes, but a 2 or 3 point bump in hardness would not turn an easy to sharpen S35VN into a stone killing monster.

To put it blunty, the benefits of a hardness bump would far outweigh the detriments.


ETA: you say you have "welded chips back in?" The steel used in welding rods isn't even close to the composition of knife blades. Are you sure you really mean what you're saying? That wouldn't work on any modern cutlery steel, lol.
 
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ETA: you say you have "welded chips back in?" The steel used in welding rods isn't even close to the composition of knife blades. Are you sure you really mean what you're saying? That wouldn't work on any modern cutlery steel, lol.[/QUOTE]

I worked in a place that had a huge tool and die dept. I traded favors with one of their welders who would tig weld it back in and re heat treat it. The welding dept had various filler rods depending on the types of steel used. We did injection molding as well so the tool steels we used were often almost identical to what crucible is putting out, and in some cases may have been made from crucible.

So no I didn't just strike up an arc with a 7010 welding rod and have at it. As you say that would have destroyed the blade. Any type of mig or stick welding would destroy the metal. However, you can do some amazing things with tig if you have a good welder with the appropriate knowledge of metallurgy,and heat treating the metal.
 
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