S7 shock steel vs 440A

[out5yder]

Hello,

Which steel is better in regards to destruction resistance (chipping, breaking, edge rolling etc.) between S7 and 440A?
I know the obvious teoretical answer: "S7, of course!". But as all of us can see from the destruction tests, the Cheaper Than Dirt stood better than the Scrapper 6 by holding its tip and edge much longer (just watch how the edge looks like at the metal-on-metal test for both knives).

So, can anybody explain that?

Cheers!

[dingyu1980]

i think the scapperyard 6 that has been tested by noss may be a defected one , it is said that SY has a problem of Metallurgy that some small air Gaps contained in the metal somewhere on BF . so, another de-test on SY knife will be valued , but··· i can not offer one and donate it to great man Noss:rockon:

[out5yder]

i think the scapperyard 6 that has been tested by noss may be a defected one , it is said that SY has a problem of Metallurgy that some small air Gaps contained in the metal somewhere on BF .

I know scrapyard had some issues with air gabs in the steel some time ago, but I don't think the tested knife was defected in this regards. The steel itself was clearly deforming easier than cheaper than dirt (the tip got deformed on the first few strikes and the entire edge was rolling and after that chipping). So, it could had been be defect in regards to heat treatment but there was obviously no air gab.

When there is an air gab in the steel you see geometrical shaped pieces chipping out of the steel (this kind of defects can be seen on blade forums in pictures all over the place). But steel deformation does not occur due to this kind of problems.

However, there is something I still cannot understand: how could a 58-60 HRC blade in S7 deform easier than a 440A blade of the same kind, during the same set of tests?

[Madnumforce]

I know scrapyard had some issues with air gabs in the steel
However, there is something I still cannot understand: how could a 58-60 HRC blade in S7 deform easier than a 440A blade of the same kind, during the same set of tests?

Hardness is just a very limited element to define mechanical proprieties of steel. You have to also consider elastic limit (or yield strength, the force per section up to which material still in elasticity domain, and come back straight after deformation), ultimate strength (force per section to break the material), resilience (impact force to break a standardized sampl), etc...

[out5yder]

Hardness is just a very limited element to define mechanical proprieties of steel. You have to also consider elastic limit (or yield strength, the force per section up to which material still in elasticity domain, and come back straight after deformation), ultimate strength (force per section to break the material), resilience (impact force to break a standardized sampl), etc...

I think this might explain the things... But should I understand 440A is a better steel in regards to destruction resistance? Than here naturally comes another question: "Why knife manufacturers avoid using it in hard use knives?" (for example: Cold Steel uses SK5 in their low cost Bushman. Why don't they use 440A? (440A would also have the advantage of stainlessness and it would probably be cheaper to heat treat).

[dingyu1980]

as i know , 440A, was a cheap one !
if a Manufacturer produce knives using 440A, can sell it up to 100$ or above? no way .
so , if i were a manufacturer , i will use expensive steel , to make more money, do not use cheap ones, no matter what is the performance of that !
hahaha , just a kidding:rockon:

[Madnumforce]

I think this might explain the things... But should I understand 440A is a better steel in regards to destruction resistance? Than here naturally comes another question: "Why knife manufacturers avoid using it in hard use knives?" (for example: Cold Steel uses SK5 in their low cost Bushman. Why don't they use 440A? (440A would also have the advantage of stainlessness and it would probably be cheaper to heat treat).

In fact, 440A (or B, or C) doesn't mean much now. It's an american norm for middle carbon (~0.6% to ~0.75% C) stainless steel. Every other element or the way of processing steel is not included under this very general norm. Many chinese steels (on chinese made knives) were named in american standard (440 A, B, C) during the 90's, maybe not the most accurately possible. It seems they took the habit. So when a knife made in China indicates any 440 steel, it might as well be a very basic and not consistent one, as a very good steel that's also used on more expansive knives sub-contracted in China (or the manufacturers may just cheat and use another norm to make this steel appear more high end). Chinese have made huge progress in steel, and while the imported knives from the 80's and 90's had bad reputation, now many brand sub-contract with confidence and give good product to a very fair price.

[Noss]

It's on the soft side also. Many makers don't want to make blades as soft as the CTD knife. I'm not sure how well it would perform at 58-60 RC in a D-test. At the lower hardness the steel used in the CTD knife is very elastic.

[nobbs70]

Fox cutlery makes his Gurkha and his Kukri of 440A, and they are both very good pieces, and above 100$, here in Spain at least

http://www.teraasekeskus.com/tuotteet/isotveitset/FoxGurkhaNewNet.jpg

I sold mine, and now regrets it, sigh!...

[Falcor]

Dingyu1980 - I am 100% in agreement, joking or not that 'cheaper steels' cannot fetch as much as so called 'higher' steels, so manufacturers can charge higher, hence make more in margins. This is business.

Of course most of the 'higher' steels cost more to manufacture, but no where near the ratio of the price difference. Furthermore, there are every few folks who know how to properly heat treat the higher steels - e.g. Chris Reeve knives, these should and must be tough but are brittle.

Take for example the Buck Strider in 420HC; if based on performance alone this knife should be US$400+, but because it is in 420HC and not, say 3V or 154CM, you can get one for around US$120-180, yet I would trust my life on this knife.

I am waitingto see how the Barkie's do in the D tests - anyone else as keen as me to see teh results?

[dingyu1980]

now , i think of another D-test on SY knife is necessary .

[bld522]

Fox cutlery makes his Gurkha and his Kukri of 440A, and they are both very good pieces, and above 100$, here in Spain at least

http://www.teraasekeskus.com/tuotteet/isotveitset/FoxGurkhaNewNet.jpg

I sold mine, and now regrets it, sigh!...
That answers a question I've had for a long time. A.G. Russell sold a Kukri a few years ago that was made in Italy. I always thought it was manufactured by Fox, but your picture of their Gurkha was the proof I was looking for. Here's a pic of the Kukri from the Fox Cutlery web site:

http://www.foxcutlery.com/files/I/n/InNvET6FJ5dqDnNmi4rfrJHuanvnYN.jpg

It's a spitting image of the A.G. Russell Kukri. BTW, the Kukri fox made for A.G. Russell was constructed of 440B, not 440A. And I still have mine. :thumb:

[nobbs70]

Yep, I remember that one too...it was a dificult decision between the kukri and the gurkha, I took the later for the "total convex" grind, wich I fancy a lot

Funny thing, the screws look odd, mine had torxs

The new line is made in N690 (marketing alarm! :headbang:), not a bad steel at all, of course, but no better for a chopper, I think