Does the Thumb Hole weaken the steel?

[Blerv]

Almost all functions come at a price. Start with a bar of steel, harden it, grind it (or visa versa), drill it, make it fold into a handle...sure it's weaker but you just formed a pocket knife. Almost everyone would say the advantages in this situation outweigh the negatives, at least for the purpose the tool was designed to perform.

Spyderco seems to engineer their produces nicely for the average customer. In fact, they tend to treat their steel a bit harder and grind their edges a bit thinner (per classification). They walk a pretty fine line between durability and performance. If you want a pry bar I would use something else though...like a pry bar .

[anagarika]

Exactly. Any hole is a stress raiser. You can also check vininull's youtube where he compared Tenacious with RAT1, both broke at the hole, although Tenacious tip snapped first.

From this lesson, I'd use the knife for cutting and not prying. In the case of emergency, sometimes we have no choice though, so a broken knife used to safe ourselves might worth it, but also might fail to safe ourselves (if it breaks before the task accomplished). YMMV

[JNewell]

Weaken the blade? Probably. In a way that is significant at any rational level? Not a chance. In a way that is meaningfully worse than other thumb opening devices, such as studs? Not likely.

[chuck_roxas45]

Weaken the blade? Probably. In a way that is significant at any rational level? Not a chance. In a way that is meaningfully worse than other thumb opening devices, such as studs? Not likely.

I was gonna say something along those lines but that's much better said.

[arty]

I hate to quote Mike Stewart, but he said that any folder is already broken, and I paraphrase here. Folders are not going to be as sturdy as fixed blade knives made of comparable materials. A hole in the blade will reduce strength, but I wouldn't do the same work with a flexible fillet blade as with a Hi chiruwa AK kukri. I have an old Gerber fillet knife that is too flexible and not good for cleaning fish. I need a stiffer blade for that.
Pocket knives are for cutting, and not for chopping. Lots of people break the tips off of blades with fine points. The moral of the story is to avoid stabbing trees with your pocket knife with a fine, thin blade, unless you are attacked by the tree.If you don't jump up and down on your pocket knife, it should be fine, hole or no hole in the blade. ...ouch!
There is a video online of someone in heavy boots putting his entire 200+ pounds on the side of a knife. It broke after some effort. What a surprise.
I am not worried at all about the Spydie hole in a knife blade. I generally prefer to avoid holes in fixed blade knives, since they are mainly decorative and can be a source of collecting muck on a user. If you are worried about the strength of a blade, you should use a fixed blade knife for these rough and demanding tasks...or a crowbar, kukri, axe or something else.
I often have a Chaparral in my pocket and have never worried about the 2 mm thick blade. It is sturdy enough for what I use it for.

[demoncase]

If we are starting to worry about the ultimate tensile failure of a blade due to a Spyderhole then we need begin to worry about the 'stress raisers' from things like jimping (which often has sharp corners- the horror!), serrations, saw-backs, the little dimple for the detent on liner locks- or even the fingernail nick in that old-school penknife.....

I don't worry about the hole. Sal's product has never come close to letting me down materially when used as intended.

Frankly, unless I've left my brain in my other jacket and have decided to use one of my Spydies for prying up 30lb cast iron drain covers in the carpark, my office-soft hand is going to "catastrophically fail" a long time before the blade does.

Yes, the pictures of snapped PMs and such are shocking- but the plural of anecdote is not data. :D

[Holland]

People are way to concerned with the "strength" on knives these days... especially threads about lock really bother me. If you use the knife as a knife it wont break.

[Laethageal]

I don't wanna steal that conversation, but isn't the military we saw in picture on the 2nd post one of those cheap chinese fake anyway? From the look of the scales, and the box under the knife... No surprise it would break apart!

[The Deacon]

I don't wanna steal that conversation, but isn't the military we saw in picture on the 2nd post one of those cheap chinese fake anyway? From the look of the scales, and the box under the knife... No surprise it would break apart!

Nope, it's a genuine Peel Ply Carbon Fiber Sprint Run Military and, assuming the box is the one it came it, it's one of the early ones. I'm certain Spyderco was still using the grey boxes when the CF/S30V Sprint Run came out, and fairly certain it was still being used when the CF/BG-42 Sprint Run was released.

[Laethageal]

Thank you for correcting me.

[hunterseeker5]

Has someone mentioned yet that there are more than a few knives with thumb studs that fail at the thumb stud? Likewise IIRC a few of the over-hardened ZDP mules failed running up the blade to the spyder hole, and those have vestigial little spyder holes.

[Holland]

Has someone mentioned yet that there are more than a few knives with thumb studs that fail at the thumb stud? Likewise IIRC a few of the over-hardened ZDP mules failed running up the blade to the spyder hole, and those have vestigial little spyder holes.

impressive haha

[chuck_roxas45]

So maybe knives marketed as hard use shouldn't have thumb holes? Or is that just a fluke? I know travis uses his striders for more than paper cutting. :)

Has someone mentioned yet that there are more than a few knives with thumb studs that fail at the thumb stud? Likewise IIRC a few of the over-hardened ZDP mules failed running up the blade to the spyder hole, and those have vestigial little spyder holes.

[tvenuto]

Don't really want to prolong this, but I think it should be mentioned that if the blade tapers to a point, at some point the distance from edge to spine will be shorter than the distance from edge to spyderhole. So, even if the blade maintained the same thickness (which most don't) this area would be "more problematic" than the area with the hole. As was pointed out already, most of us don't notice because we use the knives as knives.

[Kweb]

As long as the knife isn't used for takes like prying it shouldn't be an issue.

[Bill1170]

So the only real additional stresses could be from the threading the of thumb-stud models and this would likely be minimal correct.

I think you are right about that, minimal because the threads go in a helix. Sharp grooves going straight through the hole would be much more likely to initiate failure.

[hunterseeker5]

So maybe knives marketed as hard use shouldn't have thumb holes? Or is that just a fluke? I know travis uses his striders for more than paper cutting. :)

I'm not even saying Striders are weak knives (although S30v is not a hard use steel so wouldn't have been my first choice) I'm just saying that when things fail they tend to fail at their weakest point. The blade acting as a lever arm, and its taper, mean that further up it'll break closer to the point. Shove the knife in further and bend and it'll break at the hole. Eliminate the hole and then what? It'll maybe blow out at the pivot, or the G10 will fail, IDK. I've seen knives fail through the tang and detent holes. The point is that everything has a limit, that limit being based on its weakest point, and when you pass that you get failure. Without a force measurement, and a relevant scale that explains that measurement to your average joe, all you are doing is proving that you can break something which can be broken. THAT is my point.

Just as an example, if it required 500 pounds force to break a spyder through the hole (completely arbitrary number and with irrelevant vagueness to boot) and 300 pounds force to break a benchmade and it just broke at the plunge line, you might falsely conclude that the spyderco is the inferior knife if all you did was assess where it broke from pictures. You're not really looking at how much force was required to break it, and while you may be right the knife wouldn't have failed at that point or at that force if the hole hadn't existed, its not a scaled metric its just speculation; for all you know at 502 pounds force the knife would have blown out at the pivot so filling in the hole would have provided no practical performance gain. How is that for an explanation?

I thought I'd also mention that I've blown a .33 inch Busse in half. It was a hard use steel on a hard use knife. Is it weak because I can break it? What if they'd made it even thicker, would that have made google images of it broken look better? No, and no.

[tvenuto]

Your claims to have broken a Busse are clearly impossible. If you attempt to break INFI, all you will do is damage all knives with inferior steel in a 1 mile radius.

[Cliff Stamp]

As long as the knife isn't used for takes like prying it shouldn't be an issue.

If those knives are not used for tasks like prying then the knife design makes no sense. Spyderco's typical folders are *far* over built for light cutting, and if that is all you are doing they are the wrong choice. A knife which is made to not take lateral loads looks like the Havalon and that knife will out perform a Spyderco significantly for that work which it has to as that is exactly what it is designed to do. However it is trivial to break the blades on the Havalon under lateral loads - which is the main complaint about them and the restriction they have in use.

In general, while the holes do weaken the knife in an absolute sense as do thumbstuds and anything which reduces the amount of steel in the blade - they are usually not a practical limitation because if they were not there the knife would still likely fail, just somewhere else such as the handle, pivot, lock, etc. .

[Officer Gigglez]

Well, folding knives shouldn't be used for prying anyway. That's a thick fixed blade's job. And chances are that if you're prying with a folder, the mechanism will break before the blade.