Spyderco Southard blade failure with pics

Wow... I've never seen an internal stop pin design that leaves so little material towards the tang. Crazy.

That shouldn't matter.
The front part of tang transfer the load to the pin. The back side should not be working.
It failed, it happens sometimes to everything.

But I must agree that the cut-outs are quite "radical" :)
 
While I'm not a metallurgist, I did study a little failure of materials in engineering school. What i don't see is from the picture are areas of striation(slow crack growth), fatigue, corrosion, creep or any other slow(er) modes of failure. Looks like a 'catastrophic' shear fracture to me. Perhaps a defect in the manufacture, or worse, design (yikes). Would be very interesting to see Spyderco's explanation of the failure. Lucky the blade was in a block of wood and not 'free' as it would be if you were cutting a loop of rope. You have my interest...please keep us posted with how Spyderco responds.
 
That's nuts. I've always been a little iffy when it comes to the longevity of knives with internal stop pins, but I know the team at Spyderco knows how to produce a fine knife. Sorry it busted, but I'm positive they'll take care of it for you.
 
I'll be that guy people will poke fun at and say I avoid internal stop pins like the plague for this very reason. You either have to have a thin engagement tang or a thin stop pin unless the knife is huge. No thanks.

Another reason to be a huge fan of thumbstud stop pins.

Speaking of which, I just finished taking pictures of my new Vallotton.
 
Another reason to be a huge fan of thumbstud stop pins.

Speaking of which, I just finished taking pictures of my new Vallotton.

I actually prefer frame captivated external stop pins. I love my 0350, but more than once when I've been using it hard the thought of them coming unthreaded or snapping has crossed my mind.
 
I actually prefer frame captivated external stop pins. I love my 0350, but more than once when I've been using it hard the thought of them coming unthreaded or snapping has crossed my mind.

Oh I've seen your 0350. If those studs haven't screwed up by now, they ain't gonna! :D
 
Oh I've seen your 0350. If those studs haven't screwed up by now, they ain't gonna! :D

It's going in for a new blade next week, so hopefully that includes new studs as they're a bit polished now.

So OP, don't worry too much. With a good company behind the work you'll get taken care of.
 
From my limited knowledge of failure analysis, the gray, more granular part of the failed part, as mentioned above, is where the catastrophic or instant failure occurred. The shiny part, if it exists, is often a longer lived crack and or defect where the two sides of the crack/material have been rubbing together and have become "polished". In a load/unload condition, sometimes these "cracks" will make a creaking noise. Just me blabbing. It doesn't sound like this is relevant to this situation.
Despite my engineering background, telling me that something doesn't need to be as massive as I'd like to be "strong enough", I still gravitate toward the more massive. I'm sure, the Southard has been well designed and thoroughly tested and this has more to do with a defect of some type. Mike
 
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Atakdog- you took a nice picture of the break on the blade side. For shts and giggles, could you take and post pictures of the break on the tang side? There are two failure locations, tang side and blade side. I'm tending to believe the tang side may have been the first to fail (maybe happening a while ago, unbeknownst to you.)

What I'm having trouble figuring out is how the blade side failed without deforming the pivot radius cutout and without disfiguring or blowing the tang side tail piece completely out.

I apologize for geeking out, but I'm fascinated on how this thing busted!
 
Thanks for posting this and all the great photos.

Somehow I've managed to miss all this inside stop pin stuff up to now.

Good to know.
 
That sucks to see happen. Send it in and they will take care of it.

The directional force and therefore pressure of the blade while in use is on the frame lock and the thick part of the blade where the stop pin is. The thin part of the blade is mostly as a guide and the other thin part where the stop pin connects is really not a big deal. That's just to keep it closed at a certain depth inside the handle. Maybe what happened is while it was closed, a strong enough force was applied to crack the blade and later on in use the rest/complete failure occurred.
I love my southards and I'm not against internal stop pins at all. It's all about the engineering.

Also it's a folding blade. If you want something for hard use and safety for the thought stuff, fixed blade. Different tools for different jobs. Phillips and flats heads are both screwdrivers. A flat head will work in both types of screws but a Phillips will only work in one.

Some of the best Spyderco come out of Taichung Taiwan.
 
One had better make really straight cuts with a design like that. The lateral forces probably got it during carving, pass.
 
Wow, sorry about your luck OP.

I'll be following along to see how this shakes out.
 
For anyone thinking it may be a fake go here, http://www.bladeforums.com/forums/showthread.php/796442-Spyderco-Fakes-amp-Knock-Offs-Info/page14

I don't think it is a fake. Also, someone asked why an internal stop pin. A big reason I believe Spyderco did it was to make the flipper incorporation easier. It looks better in most people's opinions as well. That is not to say all flippers have to have an internal stop pin because we know there are plenty that aren't, but I recall that being a reason. Another factor is simply that Brad Southard designed this knife. I personally would not shy away from the design, but attribute it to a flaw in the steel.
 
Looks like something went wrong during the manufacturing process of that particular blade and caused a fracture failure. It happens sometimes even in critical aircraft hardware. I'm sure it's not a design flaw and Spyderco will replace it.
 
I think you're lucky that when the blade broke off, it didn't fly off and injure you.
 
A Domino looks like this, very similar. Easily a strong enough design for cutting things. Now, if one wishes to rely on impact rather than sharpness, perhaps a chisel might work better... (Not implying anything about the OP, just an observation).

2safcl5.jpg

If you compare that photos of Domino blade to the Southard blade below...

Here are some photos I just took of mine. The initial pics of the broken blade did look alarmingly odd but after taking it apart it makes a little more sense. The stop pin is only in contact with the weakest point when the blade is closed. (pic 4) Exactly why the OP's broke I'm unsure of...

IMG_20140110_244410802.jpg


IMG_20140110_242435010.jpg


IMG_20140110_242502906.jpg


IMG_20140110_242541021.jpg

.... you may notice an important difference: Southard blade is further weakened around internal stop pin area because unlike Domino it has no choil and the grind line comes very close to the pin cut-out.
I still recognize that the actual cause of the disaster was likely an issue with the blade heat treat, but as somebody who does not trust ISP design, I would be concerned about how it's implemented in this particular case.
 
If you compare that photos of Domino blade to the Southard blade below...



.... you may notice an important difference: Southard blade is further weakened around internal stop pin area because unlike Domino it has no choil and the grind line comes very close to the pin cut-out.
I still recognize that the actual cause of the disaster was likely an issue with the blade heat treat, but as somebody who does not trust ISP design, I would be concerned about how it's implemented in this particular case.
Could be wrong,but I believe it the thick side of the cut out grove that holds when in the locked position?
 
Could be wrong,but I believe it the thick side of the cut out grove that holds when in the locked position?

You are right. And I was talking about it: it would be thicker if the blade had a choil, like Domino blade has.
 
My BIL is a metallurgist engineer for the DOD and we often discuss failure in machined metals. If something happens to a military aircraft part he determines what caused it to break.When contractors submit bids for metal parts/hardware he also has to determine if the product is up to specs for it's intended purpose. Even with all these inspections,failures occasionally occur.
 
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