SM-100 Myth debunked...

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Was I the only one cringing watching the second video? I was waiting for him to slip when he had the 4x4 up against his leg and was forcing the tip on the knife straight down. Then when he did stab himself in the leg a little later doing something equally as stupid, I turned it off. Hard to take a grown man seriously when he has less common sense with a knife than my 6 year old niece.
 
I'm stepping back in for a second. :o

Disregarding the matter of performance, I think the reason this steel is so expensive and used on high end, almost art, knives is because of it's aesthetic properties. this is a very uncommon steel, Elliot Williamson is the only maker I can think of that uses it with any frequency. probably up there with CPM REX 121, stellite 6k, and S125V. you won't find many knives in these steels, and I think it's part of why SM-100 sells. And everyone knows how collectors like exclusive things. Take a look at this Duane Dwyer, I believe this one sold for about $1250, I think we'd all agree this knife wouldn't be half as nice (aesthetically) without the ano on the SM-100, I think so anyway.

image_zps774774be.jpg


I don't know where I was going with that, but I think it's a valid point. :)

Cheers,
Kirby
 
Bugout Bill said:
Cliff Stamp did an evaluation of an SM-100 fixed blade from a custom maker named Jeremy McCullen (a very talented guy). The results were pretty interesting.

The link for anyone who cares (or can stand Cliff Stamp):

http://www.cliffstamp.com/knives/forum/read.php?6,15032

http://www.cliffstamp.com/knives/forum/read.php?3,15044,15068#msg-15068

http://www.cliffstamp.com/knives/forum/read.php?3,15081,page=1
Click to expand...

I read through it, and I knew I smelled a rat for a reason. This is not some magical mystery material that is the best thing to happen to knives ever. If you MUST have nonmagnetic, this is a good option, but if you can stomach being magnetic you will be much better suited with H1 or similar rust free steels. If you don't need toughness but need nonmagnetic and cutting performance, you can go ceramic. If you need tough and nonmagnetic but edge retention isn't vital you can go with titanium alloys.

It seems that SM100 is a midpoint between edge retention, corrosion resistance, and lightweight with a side of being nonmagnetic that almost nobody needs.
 
Tom Mayo makes SM100 knives and they are quite popular. I don't think he'd use a material that was not good for blades.
 
Did a quick search on the web for the tensile properties. According to their website SM100 is based on the composition of nitinol 60, which is 50.62at% Ni and the rest Ti. Take a look at the stress-strain plot for the alloy shown here:
http://www.sciencedirect.com/science/article/pii/S0921509302001223

The area under the graph represents the amount of energy required to break it. Although this sample was only heated to about 1500F, if you look at the Ti-Ni phase diagram the extra heating to 1800F (about 1000 C) just brings it into the pure TiNi phase at the material composition which is possibly an important phase transition. But I couldn't find anything heat treated this way.

The phase diagram is here: http://oregonstate.edu/instruct/engr321/Homework/HomeworkW00/HW5gifs/HW5u.gif

Compare that stress-strain curve to that of a 1045 martensitic mild steel: http://www.scielo.br/scielo.php?pid=S1517-70762010000200022&script=sci_arttext#f5
You'll see that SM100 (or something close) cooled from 1500F is rather unimpressive. It's possible that it enters a TiNi single phase when heat treated the recommended way, then undergoes some sort of diffusionless, martensitic transformation when quenched but that hasn't been documented as far as I know.

If anyone has access to a uniaxial tensile testing machine it'll be interesting to perform some tests on a heat treated sample :)
 
dkb45 said:
I read through it, and I knew I smelled a rat for a reason. This is not some magical mystery material that is the best thing to happen to knives ever. If you MUST have nonmagnetic, this is a good option, but if you can stomach being magnetic you will be much better suited with H1 or similar rust free steels. If you don't need toughness but need nonmagnetic and cutting performance, you can go ceramic. If you need tough and nonmagnetic but edge retention isn't vital you can go with titanium alloys.

It seems that SM100 is a midpoint between edge retention, corrosion resistance, and lightweight with a side of being nonmagnetic that almost nobody needs.
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That's what I gathered as well. Seems to be an answer to a question that hardly anyone has asked.
 
shqxk said:
No. no at all, that was absolutely false. Sound like you almost have no clue about metallurgy.

No quality chef knife which made from a good steel with good heat treat will fail the same way as the video...
Even ZDP-189 heat treated to more than 65rc won't snap off by light pressing against a pen.

The fact is SM-100 has very low young modulus from the data sheet. http://www.summitmaterials.com/sm-100/knives/ Not much higher than concrete. Young modulus directly refer to material's shear strength. In this case it isn't any surprise for SM-100 to snap off just by light lateral force.

Contract the maker for any fact would be a bad idea since anyone would speak for himself to defense for his business.
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I have no data on this material, nor really care about it.


[edit I see now you said "failed like in the video". as I have no interest in watching the video I can't say one way or the other. but yes, it's very easy to destroy a good edge with lateral pressure from a pen]
but you're wrong about the knife edge not failing from pressing against a pen. hell, nearly every law of physics shows that a nicely ground and hardened knife for the kitchen can fail from the huge pounds per square inch exerted onto it in a lateral force by a pen.

Murray Carter even shows it on his own knife made of White Steel, which should be "tougher" than a similarly hard zdp blade.

no, it shouldn't fail from "light pressure". but can you really judge light pressure from a YouTube video? I don't think you can. and remember exerting ten pounds of force on an edge with a pen equates to much higher pressure than if you used a flat piece of metal instead.
 
but yes, it's very easy to destroy a good edge with lateral pressure from a pen
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Then that would not consider as a good edge.

You are too much theory crafting man, i suggest you do buy some Spyderco's Endura ZDP-189 and try pushing the very tip point of the blade against a surface of glass with 10 pounds of force. You will know that a well hardened steel are much tougher than what you give credit for, and yes, I have done this kind of testing with numbers of steel type.
 
9blades said:
I'm stepping back in for a second. :o

Disregarding the matter of performance, I think the reason this steel is so expensive and used on high end, almost art, knives is because of it's aesthetic properties. this is a very uncommon steel, Elliot Williamson is the only maker I can think of that uses it with any frequency. probably up there with CPM REX 121, stellite 6k, and S125V. you won't find many knives in these steels, and I think it's part of why SM-100 sells. And everyone knows how collectors like exclusive things. Take a look at this Duane Dwyer, I believe this one sold for about $1250, I think we'd all agree this knife wouldn't be half as nice (aesthetically) without the ano on the SM-100, I think so anyway.

image_zps774774be.jpg


I don't know where I was going with that, but I think it's a valid point. :)

Cheers,
Kirby
Click to expand...

Of course. Aesthetic and material rarity is a valid and good reason to use such material. The same way some makers use mamooth tooth for handles.
Is it better? No, but nice and rare.

BUT, if a maker/producer stands that such material jest better that traditional, he should be able to prove if without problem, right?
Or, said material should be on par with standard materials, when you concentrate on single property - like non-magnetic.
 
Thomas Linton said:
So who thinks Tom Mayo makes - and sells - knives that shatter at a glance?
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No one is saying he does.

People are blowing the video of the kitchen knife exploding out of proportion.

It was a kitchen knife with an extreme grind that may have experienced embrittlement during grinding. None of the of the other videos have experienced such dramatic failure.

dkb45 said:
I read through it, and I knew I smelled a rat for a reason. This is not some magical mystery material that is the best thing to happen to knives ever. If you MUST have nonmagnetic, this is a good option, but if you can stomach being magnetic you will be much better suited with H1 or similar rust free steels. If you don't need toughness but need nonmagnetic and cutting performance, you can go ceramic. If you need tough and nonmagnetic but edge retention isn't vital you can go with titanium alloys.

It seems that SM100 is a midpoint between edge retention, corrosion resistance, and lightweight with a side of being nonmagnetic that almost nobody needs.
Click to expand...

This is probably the best assessment of this steel.
 
Thomas Linton said:
Therefore:



So now we see which myth was debunked.
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OP was saying that SM100 is not the greatest thing ever. I think it has been proven that it is arguably better than Ti, which isn't saying a whole lot. However, the OP's assertion that SM100 will fragment explosively is false.
 
The claims that SM100 is a revolution in knife material is plainly a myth. Further use of that blade showed it would fracture while trying to push cut through 3/8" hemp rope. Now, the SM100 blade was ground very thin for use as a kitchen knife, but I've never heard of any knife behaving like that just cutting rope. As I said above, the thought is that there is something wrong with this knife in terms of grinding heat or something such as that. Blades of the same bar of SM100 did not behave this way, though they were left thicker.
 
Does anything in this thread tell us about the characteristics of SM-100 as opposed to the characteristics of this blade?

Think of how many come here asking not about the maker but about what steel they should pursue - about D2 instead of about Dozier. Those are the folks who get burned in the search of blades of Unobtainium, not the buyer who seeks the master maker.
 
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