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I was wondering from a structural position if an opening hole in the blade makes a blade weaker than one with a thumbstud.
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Do opening holes make blades weaker?
- Thread starter curious2003
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Of course it makes the blade weaker - after all, it's a hole (meaning removed material).
But that effect is really miniscule, especially because the no. 1 breaking point in folders is the pivot pin (when lateral stress is applied).
I think it's more likely that a folding knife will completely fall apart before the blade breaks because of an opening hole.
But that effect is really miniscule, especially because the no. 1 breaking point in folders is the pivot pin (when lateral stress is applied).
I think it's more likely that a folding knife will completely fall apart before the blade breaks because of an opening hole.
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I'm not an engineer, but from what I understand, sometimes having holes can actually make a part stronger if done correctly. It has to do with how much surface area is exposed if I remember correctly.
A good example would be that in many applications a tube isstronger and more resistant to bending than a rod of the same mass.
Perhaps one of the more engineering types here could elaborate?
jmx
A good example would be that in many applications a tube isstronger and more resistant to bending than a rod of the same mass.
Perhaps one of the more engineering types here could elaborate?
jmx
I think they concluded (from the "blood groove" discussion) that there is no way to make anything stronger by removing material. There could be significantly higher mass/strength ratio, and could be just as strong, but can't be made stronger by using less material.
The opening will make the blade weaker, but all the important points have been covered. You are probably going to break the tip or the handle/pivot pin before the base of the blade will be affected by the hole.
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phatch
yes i have read the other posts on the topic
i only found that after i started this thread but it never hurts regardless to hear from new people
yes i have read the other posts on the topic
i only found that after i started this thread but it never hurts regardless to hear from new people
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- Oct 3, 1998
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- 4,842
I think Cliff has mentioned in the past that he's tested it out and the hole does make the blade noticeably weaker. On the other hand, I'm pretty sure the number of knives Spyderco has had returned due to breaks at the hole is around 0. For practical purposes, the very real opening advantage of the hole is more important than any blade strength that's sapped off, IMO.
Joe
Joe
Cliff Stamp
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Joe Talmadge :
The tips go long before the blade body usually as it is rare to pry to almost full blade length with a folder. You can break the tips on most folders very easily with just a twist of the wrist, cracking the blade in half requires the use of your shoulder, though large blade holes make it much easier. I would agree in general that it makes little difference in overall functionality as the knives would still be readily broken even without the holes as the blade stock on folder is thin. If you were making a prybar class folder however, the effect of blade holes and the like should be examined.
-Cliff
The tips go long before the blade body usually as it is rare to pry to almost full blade length with a folder. You can break the tips on most folders very easily with just a twist of the wrist, cracking the blade in half requires the use of your shoulder, though large blade holes make it much easier. I would agree in general that it makes little difference in overall functionality as the knives would still be readily broken even without the holes as the blade stock on folder is thin. If you were making a prybar class folder however, the effect of blade holes and the like should be examined.
-Cliff
A chain is as strong as its weakest link. The area around the opening hole is not the weakest point of the folder, so it doesn't really matter. Yes, the hole makes it weaker, but not weak enough so that it matters.
Somebody might say that this is a generalisation and is not scientific enough, but if anyone wants to play scientist, here is a little engineering quiz:
PhoulPlae said that you cannot make a part stronger by removing material, and this is correct, if by "stronger" we only measure tensile strength. BUT there is a case where you can remove material and increase the life expectancy of a part. How can this be?
If you can't figure it out, read the next post.
Somebody might say that this is a generalisation and is not scientific enough, but if anyone wants to play scientist, here is a little engineering quiz:
PhoulPlae said that you cannot make a part stronger by removing material, and this is correct, if by "stronger" we only measure tensile strength. BUT there is a case where you can remove material and increase the life expectancy of a part. How can this be?
If you can't figure it out, read the next post.
It has to do with fatigue, for example under cyclic (repetitive) loading. In such cases, small hairline cracks that have formed at the surface of the part (or even notches that we have cut into the material due to bad design)are areas where fatigue cracks start and then propagate throughout the material, until the part breaks (after many many load cycles of course).
In such a case, if you remove enough material to "erase" the crack or to "radius" the sharp notch, you can make the part to last much longer, even if it is not "stronger" in absolute tensile strength.
In such a case, if you remove enough material to "erase" the crack or to "radius" the sharp notch, you can make the part to last much longer, even if it is not "stronger" in absolute tensile strength.