Slysz Bowie Blade Broken: FFG+Spydie Hole Fail?

[funghiman]

It comes from a misfortune experienced by a knife modder that one of my friends known, and might affect someone who are planning to own or have already own a Slysz Bowie, including myself.
To make things clear, I'll call this friend B, and the modder C in order to distinguish.

When C was finishing an order on a Slysz Bowie, re-profiling the blade to give it a total satin finish, he snaps the blade in two pieces, and the crack was right across the hole. He took some photos (and authorization to quote them are still pending), posted them to his social media and complained about how much he had to compensate to his customer. B saw this, and forwarded the words to me, and then we had a few hours talking about this.
The break actually took place after both sides of the V-grind are treated, at the point C was giving the satin finish to the remaining interface where blade meets handle through washers.

Neither B nor I am metallurgy experts, but throughout the discussion we both agreed that there is no simple cause that leads to this.
First we looked at the grinding of the blade. I myself has a huge fan of Spyderco FFGs, they are usually strong and sleek, performs super clean cuts. But if you add a hole to the grind shed, i.e. where the V begins, things may start to become a little tricky. But things are not that bad, Spyderco uses laser to perform the cuts, and does well making sure there are obvious structural weak point around the circle. Even among the rare cases of Spyderco Blades fractured under stress, few of them took place near the hole.
We kept thinking, and B came out with the point that the top of Slysz Bowie's hole is terrifyingly thin. I looked at it, and it is. But Para 2s and Manix 2s are also FFG with enormous Spydie hole, and have similar thickness at that point, why not them? And I figured out it might have something to do with the placement of that hole. Original Spyderco designs, like Para 2 and Manix 2, usually run the V-shoulder right through the hole. Although this might not be intentionally, but it does transfer any horizontal stress over the hole all the way to the pivot. But in the case of Slysz Bowie, the V-shoulder is just tangent to the hole. And without the efficient tranfer, any stress applied to the grinded surface will basically accumulate right at the top of the circle, where exactly there is least steel. Under the pressure given from the belt sander C uses for sation finishes, it's almost as doomed as an up-side-down windshield with an elephant standing on its top.

Don't take me wrong: Marcin's Slysz Bowie is originally a thumb-disc design, and I do admire his amazing work. Thumb-disc works just fine with the deep FFG (starts early from the pivot), but a large sized afterthought Spydie hole in an improper position may lead to some consequences that both Marcin and Spyderco didn't expect. C claimed that this was the first time he ever broke a blade, and he would never accept any more orders modding a Spyderco. I am still trying to get reach to him, not only for the photos but also the potential opportunity of getting the fragments to Spyderco's lab, in case Sal and his fellow are interested.

[LC Kid]

Hi funghiman!

...finishing an order on a Slysz Bowie, re-profiling the blade to give it a total satin finish, he snaps the blade in two pieces, and the crack was right across the hole...

Reprofiling the blade to give a satin finish sounds to me like Regrinding the blade.

Certainly, trying to imagine how the crack was without pics demands a lot of imagination. But to regrind a FFG 3.5mm blade requires some steady hand and a lot of experience. Not saying here the person who was trying to do so doesn't qualifies for such duty, but I really know very few people that I would look for if I wanted to regrind any of my blades, and some of those guys doesn't even regrind blades anymore.

Why would somebody want to regrind/refinish to satin the fantastic original stonewash on the Slysz Bowie's blade? :rolleyes:

My old man always told me that God's has his own mysterious ways. :D

[funghiman]

Hi funghiman!

...finishing an order on a Slysz Bowie, re-profiling the blade to give it a total satin finish, he snaps the blade in two pieces, and the crack was right across the hole...

Reprofiling the blade to give a satin finish sounds to me like Regrinding the blade.

Certainly, trying to imagine how the crack was without pics demands a lot of imagination. But to regrind a FFG 3.5mm blade requires some steady hand and a lot of experience. Not saying here the person who was trying to do so doesn't qualifies for such duty, but I really know very few people that I would look for if I wanted to regrind any of my blades, and some of those guys doesn't even regrind blades anymore.

Why would somebody want to regrind/refinish to satin the fantastic original stonewash on the Slysz Bowie's blade? :rolleyes:

My old man always told me that God's has his own mysterious ways. :D

Lol I must say C is experienced. He was once sent a ZT0620 with broken tip, and he regrinded into a drop point. I am planning to ask him for pictures of that amazing work as well.
And yes you are right it's a regrinding job on the Slysz Bowie. As of the picture I saw, on the presentation side the Spyderco logo was actually removed, imagine how much steel is that.
Why would someone prefer satin over stonewash? I dunno, but well it's the requirement from your customer right? Sometimes it's just obey or not get paid :D

[Surfingringo]

Hi Funghiman, I have a couple of questions. I know it will be easier to describe the issue with pictures, but I thought you could clear up a couple of things for me.

1. When you talk about the "V-shoulder" are you referring to the plunge line?
2. Please help me understand this quote:

The break actually took place after both sides of the V-grind are treated, at the point C was giving the satin finish to the remaining interface where blade meets handle through washers.

Does this mean that he was polishing the actual tang of the knife and that while doing so he broke the blade near the hole?? If this is correct then I am really confused. I don't see any way he could do that without gross error on his part. The only thing I can imagine is he had the blade in a vice and was power sanding/buffing the tang at high rpm and the sander caught an edge on the tang and "ping"...tang goes flying across the room. If this is what happened then that is not an issue with the hole but rather a case of "pilot error".

I am not blindly defending the design and if there is some flaw I'm happy to learn about it but I'm going to withhold judgement on this one until we have more information. Hopefully that is forthcoming.

[Surfingringo]

I don't think we are going to learn anything at all until we have more information and pics. It would be good to have pics of the spine as well as the break so we can see just how much stock the fellow removed. I too would be interested to know what his level of qualification is. I'm not trying to be contrary but grinding a broken spine down to make a drop point is one of the most remedial grinding jobs one can do. I have done it on many knives, including a broken Phil Wilson custom and there's nothing to it. I even posted a tutorial on here that anyone with a piece of sandpaper, a flat surface and basic motor skills can follow. But I digress....

I will say this and then I really am stepping away from this one until we have more info. The fact that the hole has been in use for several decades without showing itself to practically weaken the integrity of the blade, the fact that I have never heard of this issue occurring with a Slysz Bowie (and almost never with ANY Spyderco), and the fact that this blade was in the process of being heavily modified and weakened by someone with an unknown skill set make me fairly confident that there is no structural or design issue with the Slysz Bowie. If we find evidence to the contrary I will certainly acknowledge it but I'm not holding my breath.

[funghiman]

Hi Funghiman, I have a couple of questions. I know it will be easier to describe the issue with pictures, but I thought you could clear up a couple of things for me.

1. When you talk about the "V-shoulder" are you referring to the plunge line?
2. Please help me understand this quote:

The break actually took place after both sides of the V-grind are treated, at the point C was giving the satin finish to the remaining interface where blade meets handle through washers.

Does this mean that he was polishing the actual tang of the knife and that while doing so he broke the blade near the hole?? If this is correct then I am really confused. I don't see any way he could do that without gross error on his part. The only thing I can imagine is he had the blade in a vice and was power sanding/buffing the tang at high rpm and the sander caught an edge on the tang and "ping"...tang goes flying across the room. If this is what happened then that is not an issue with the hole but rather a case of "pilot error".

I am not blindly defending the design and if there is some flaw I'm happy to learn about it but I'm going to withhold judgement on this one until we have more information. Hopefully that is forthcoming.

1. Yes exactly I was talking about the plunge line, the word just somehow lost its way to come out of my brain.
2. I did see pictures of both grinded sides satined with the blade being still intact, and the break can only happen when he was treating the tang, cus he never had the chance to finish the work. And as to my knowledge he was using a smaller hand-held sander, and the force applied was less than 10kg, or 22lb. And he did treat varieties of other Spydercos in the past in the very same way, Para 2s, Southard Flipper, Endura, you name it.

I totally agree with you that the design could not be the only one to blame at. It's like an air crash investigation: there are mechanical problems and there is human error, the incident cannot happen if ever one component of the chain is absent. Earlier in the discussion I did doubt how in the world this can happen. I guess it could be the stress in earlier grinding has already built up in the blade, and the last step just act like an igniter. But no sure conclusion can be drawn if the blade wasn't retrieved and examined.

[jabba359]

Too little concrete evidence for us to analyze to make any conclusions that aren't utter speculation.

Is it possible it was a defect in that particular knife? Sure, it's possible. But with the information we have, there's no way to tell. Probably the only way to know with reasonable surety would to be looking at the break under a microscope.

[funghiman]

Well maybe I can post a few pictures first that actually I already had access to. Words and imagination can't do everything.

[funghiman]

And here are thumbnails of the 0620CF and Delica he had worked with.

[The Deacon]

My eyes may be playing tricks, but it looks to me as if a fair amount of material was removed from the blade of that Bowie. In any case, the only one's I'd trust to determine the cause of the failure are the folks at Spyderco.

[Studey]

Yeah, I know who that is. Look at the break though...you can see the angle on it, looks to me like he was pushing to hard on the blade, it was unsupported, and it broke there. Looks like an issue of being a little careless and applying too much lateral pressure to a thin blade.

[StuntZombie]

I can imagine Spyderco would still like to have that one back to check it out.

[funghiman]

Yeah, I know who that is. Look at the break though...you can see the angle on it, looks to me like he was pushing to hard on the blade, it was unsupported, and it broke there. Looks like an issue of being a little careless and applying too much lateral pressure to a thin blade.

Your guess actually makes sense, for the reason that original stonewashed surface being grinded so deep in, and even if the blade was supported, its overall structural strength has already be weakened so much. But other Spyderco knives has experience the very same modification and survived, even Slysz Bowie's little sibling, the beloved Techno. So I suppose it still have something to do with the place of that hole, given that most Spyderco folders don't have their holes exposed that forward into the grinding.

[Donut]

I've heard people say that if you don't keep the blade cool while doing a regrind, you can compromise the heat treat of the blade.

Now, I don't know what the heat treat was like before the regrind, I don't know how the regrind was done, I don't know if compromising the heat treat means it would be fragile to break or if it would actually become stronger to resist breaking.

[awa54]

Hmm.... the perils of perilously thin regrinds

[Cujobob]

I don't think it's fair to question the build quality of a knife because of something that happens after a modification to the affected area. Would this knife have exhibited any issues in the original format it was designed for? We can't say. Clearly, this knife was not designed around the intention of grinding it thinner.

I feel for the guy who has to pay for the replacement, though.

[ChrisinHove]

Ouch. Expensive. Bad luck!

[PayneTrain]

I don't know if compromising the heat treat means it would be fragile to break or if it would actually become stronger to resist breaking.

My best guess is that at those temps, you are annealing the blade and making it softer. That's why it won't take an edge after. It's too soft and weak to maintain an apex. I appear to have done it to the first chef knife I made in a couple spots, and now I grind my edges by hand. :o

Though I don't think that's what happened here. And I don't quite understand the surprise either. Every broken blade I've seen that has a hole (Strider, Spyderco, Benchmade) breaks at the hole. It's pretty intuitive. And every one (and I'll presumptuously include this one as well, because I believe it to be the case) has broken for the same reason: user error. I'm not trying to be a Spyderco defender by any means, but I mean, come on, take a step back and look at what is happening here. The guy was modifying a thin piece of steel, thinning it out even more and applying a power tool to it. And how does he know he was applying less than 10 lbs of force? And where was it applied?

He was modifying the blade. Once you've modified it, you can no longer claim a design flaw since it is no longer the original design, which of course was never designed to be modified in the first place. That case is closed. What caused it to break? Well unless it wasn't tempered properly, the only thing I can imagine causing that is the same thing that causes most blades to break: applied force. Basically, the guy made a mistake on this one. He's gotta take the L.

Sorry to charge in here with such conviction, but I'm just a huge fan of parsimony and it seems pretty obvious. I'm sure the more details you are able to give of what he did, the more obvious it will become that he just messed this one up. Clearly he has experience and does some fine work, but accidents happen! It's all good! What's more important is that he didn't get hurt in the process, unless that tape on his finger is a result of this as well.

[bearfacedkiller]

It looks like considerable material was removed. The cause of the break is that, not the location of the hole. It is my understanding that Spyderco has a calculation of sorts to determine minimum cross section of blade at the Spydiehole based on blade length and other factors and I am gonna guess that this mod took this knife well below that spec.

Modifying a knife in a drastic way and then saying that the design is flawed is just crazy.

This thread stinks.

[tvenuto]

It looks like considerable material was removed. The cause of the break is that, not the location of the hole. It is my understanding that Spyderco has a calculation of sorts to determine minimum cross section of blade at the Spydiehole based on blade length and other factors and I am gonna guess that this mod took this knife well below that spec.

Modifying a knife in a drastic way and then saying that the design is flawed is just crazy.

This thread stinks.

Ha yea, def modify at your own risk. But hey, at least we got pictures! I almost stopped reading when it started with "...so I know a guy."