Scrapyard Knives

Cobalt

Cobalt

Platinum Member
Joined
Dec 23, 1998
Messages
17,729
OK, the new line which I got a chance to see looks really nice and should give the Rats some competiton. Anyway the steel used is SR77 which is a slightly modified S7 according to the powers that be at BLADE. So I figured I would put in some stats on it compared to other steels.

S7 Impact toughness at Rc of 57 = 125 (ft-lbs)
CPM3V Toughness at Rc of 58 = 85 (ft-lbs)
CPM3v Imp.Toughness Rc of 60 = 50 (ft-lbs)
A2 Impact Toughness at Rc 60 = 40 (ft-lbs)
D2 Impact Toughness at Rc 60 = 21 (ft-lbs)

So S7 is definitely tougher than all these other steels, however, wear resistance will probably be slightly lower. It would be interesting to find out how wear resistance of this stuff stacks up.

I remember someone having Justin make an Rd9 out of S7 and the guy commented on the lower wear resistance (quicker blunting) than 5160, so it will be interesting. However, for a total abuser blade, these things should be great.
 
Nice post.... any idea when the web site will be up.... and will they have their own forum as well ?....
 
Don't know, but I doubt they will have their own forum for smetime. I guess the market dictates that. If these things take off and sell well, then maybe. They may be a limited run and die out, you never know. I got two satins so I plan on beating one up soon.

I noticed that the two satins I got came with a zero convex edge that was extremely sharp.
 
Wear resistance values for S7 are very low, it is as lopsided in that respect as it is in toughness :

http://www.timken.com/products/spec..._Files/air_melt/ColdWorkToolSteels/TLS S7.pdf

It is about a three, A2 is about a 6 and D2 is about an eight. These are all effected by cryogenics, some more than others. Note there are many ways to measure toughness besides what Crucible cites and wear resistance isn't critical to all aspects of edge holding. It would be interesting to see a public demo of performance similar to what was done with the Swamp Rats and Busse Combat knives.

-Cliff
 
I am a huge fan of S7. I think that many will be suprised at how well it holds a edge. No you will not be cutting hundred of yards of dirty carpet with it but it isn't that bad either. I have a couple of knive in S7 and want more!
 
If it bears the cryo from Ohio, I think many will be greatly surprised. I got one of the 6" models in satin and I plan on giving it a few licks when I get the chance.
 
Thanks for the head up!!!!!!

Cobalt said:
.........I got two satins so I plan on beating one up soon.

I noticed that the two satins I got came with a zero convex edge that was extremely sharp.
Click to expand...

Looking forward to the reviews, will it be post here or the rat forum?
 
These have me interested as well. How does stain resistance of S7 compare to the likes of infi or similar "semi-stainless" steels? This was the deciding factor in me not getting swamp rat blades, despite my love for resi-c handles.
 
Cobalt said:
I noticed that the two satins I got came with a zero convex edge that was extremely sharp.
Click to expand...

I'm surprised no one else had mentioned that before, at least that I saw. I got one of the satin ones as well and was really impressed with the convex edge. :thumbup:
 
yoda4561 said:
These have me interested as well. How does stain resistance of S7 compare to the likes of infi or similar "semi-stainless" steels? This was the deciding factor in me not getting swamp rat blades, despite my love for resi-c handles.
Click to expand...

I think it is less stain resistant than SR101.
 
So, S77 is "slightly modified" S7. Has the company made any statements about what the modifications are, what they hope to achieve? Did they shine any light on this at Blade? :confused: Since S7 appears to be so tough, but is potentially less wear-resistant, I might bet, for what my opinion's worth, that the Crashyard folks, recognizing this, may be aiming for a steel a little more wear-resistant - possibly corrosion-resistant too.
 
Isn't it possible to change the toughness rating by going with a higher or lower Rc?

For example, would the D2 not be tougher or less brittle in a lower Rc?

If so, do these numbers really prove anything?

Thanks for the great info.
 
Terry Newton said:
Isn't it possible to change the toughness rating by going with a higher or lower Rc?
Click to expand...

Generally yes, however you also need a high hardness to keep the edge from denting/rolling. By the time some of the more brittle steels get very tough and you don't need to be concerned about fracture any more you will have long past the point that you can notice issues with deformation. The thing about the inhernetly tougher steels is that you can get high toughness and high strength at the same time.

-Cliff
 
By the time some of the more brittle steels get very tough and you don't need to be concerned about fracture any more you will have long past the point that you can notice issues with deformation.
Click to expand...

:confused: Cliff, to make sure I'm following this (maybe I'm not). You're saying that when you bring brittle steels to lower and lower levels of hardness to make 'em tough enough so that fracture is not an issue, the trade-off is that they're now too soft to resist edge rolling and deformation in use?
 
smithsnoh said:
You're saying that when you bring brittle steels to lower and lower levels of hardness to make 'em tough enough so that fracture is not an issue, the trade-off is that they're now too soft to resist edge rolling and deformation in use?
Click to expand...

Exactly right. You also tend to lose the benefit of any wear resistance if the edge is deformint readily and now all that carbide does is lower grindability. Thus you end up with a knife that goes blunter faster and takes longer to sharpen. Most steels have a point of "optimal" performance based on their composition, what they were meant to do well. Really moving away from this point to try the make the steel do something it wasn't meant to do is rarely a good idea. This is why there are so many types of tool steels and not just one steel which can be hardened a bunch of different ways.

-Cliff
 
Which is all just fine and dandy - BUT WHEN CAN WE GET SOME OF THESE?? And where?

Man this Blade show and tell, then .................... wait is killing me.
 
TurnerIII said:
Which is all just fine and dandy - BUT WHEN CAN WE GET SOME OF THESE?? And where?

Man this Blade show and tell, then .................... wait is killing me.
Click to expand...
Seriously. I don't care how tough the steel is, or is not if I cannot buy the blade. Seems to me that it it time for Scrap Yard to bring the web site on line.
 
The Timkin web page shows that S-7 has similar wear characteristics to O-1, while the Crucible page indicates that it has slightly lower wear resistance. Anyone who's used a Randall knife may be a little dissappointed in those figures, but anybody who's used a MadDog will be quite happy. And anybody who knows a bit about how seriously Jerry and the guys take heat treating ought to expect good things. It may not be up to SR101 or properly treated D2 levels, but ought to outperform any other S-7 on the block.
That's what I'm counting on, now where do I send my money?
 
You must log in or register to reply here.
Back
Top