Ball Bearing pivots actually weaker than PB washers?

G

Gideons

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Hello BF,

I have heard so many times of people who dislike ball bearing pivots that they're weaker than PB washers. Is there any scientific proof of this? Or just something people say... not looking for pure opinions, I enjoy both pivots so no hate here. Has there been any actual scientific tests on this subject?

-Gideons
 
What do you mean by weaker?

A couple points,
  1. First; the contact area of a washer/bushing is much much larger than that of a bearing.
  2. Second; most bearings are meant to spin, usually and at high speed in a machine. A knife is going to see 180 give or take of rotation.
  3. Third; bearings are more complex with the potential for more points of failure.
  4. Fourth; you can't have it all. A knife designed to flick open with no effort repeatedly will have had to compromised some other aspect of it's performance to do so. The million dollar question is what aspect did it compromise to do so and is that going to be a problem during the lifespan of the knife.
 
Not sure that they are weaker, but washers have more contact surface area which provides a little more rigidity. But it does wear more because of the friction. As for being weaker, I think the size of the pivot is more of a determining factor than whether it is a washer or bearing. That is pure speculation not from any testing.
 
Gideons said:
Hello BF,

I have heard so many times of people who dislike ball bearing pivots that they're weaker than PB washers. Is there any scientific proof of this? Or just something people say... not looking for pure opinions, I enjoy both pivots so no hate here. Has there been any actual scientific tests on this subject?

-Gideons
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No proof what so ever. It's mostly just hate.

No knife will like side to side flexing... And ball bearings could have some issues with that, especially if they ride on the titanium and not steel bearing races... But the likely hood of the blade snapping in half would happen first most likely. But that's why a knife isn't used to pry with. And if you are prying with a knife... Successfully... Good for you. Its not the tool for that.
 
Does the washers or bearings determine strength or weakness? Is that more determined by tolerances in design and manufacturing? Are we talking weakness or strength in that a folder has side to side play? Longevity in pivot area wear? Strength as something tested by those cold steel/ Demko tests?
 
The lateral forces required to achieve indentation from a ball bearing into the titanium would likely cause problems in a washer knife as well. Both pivots are on folders, folders will have problems with large side loads. Period.

As far as reliability, I view them equal. I've yet to see a single case of a bearing knife fail where a washer knife would have succeeded.
 
But hey, if anyone has any proof of a bearing knife being in anyway inferior to a washer knife.. please provide it.
 
OP question is essentially meaningless . Too many variables involved . You could take two specific knives and do Cold Steel type or other proof testing to see which breaks first . I doubt that the washer / bearings or even the pivot would be the critical failure point for most decent knives of either type . Even these tests are often not accepted by those not liking the results . :rolleyes:
 
That thread/post shows what I think most of us would expect - more surface area, more resistant to damage. But the amount of force/deflection required... no sane person is going to stress a knife like this unless it was life or death. Even the most stressed as far as they took it did not destroy the knife, just made the action worse. Makes sense since the balls would be running over a pitted surface. Probably would be a good bit worse on a knife with a lesser ball count, 17 is quite high IMO.
 
DocJD said:
OP question is essentially meaningless . Too many variables involved . You could take two specific knives and do Cold Steel type or other proof testing to see which breaks first . I doubt that the washer / bearings or even the pivot would be the critical failure point for most decent knives of either type . Even these tests are often not accepted by those not liking the results . :rolleyes:
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That's because coldsteel tailors the 'test' to the triad locks advantage. I've had many coldsteel knives, my first was a recon 1 with the ultra lock 8 or 9 years ago. They make a good knife.

They have poor form and biased tests. But hey it's marketing and it sells knives.
 
Icehawk said:
That thread/post shows what I think most of us would expect - the more surface area the more resistant to damage. But the amount of force/deflection required... no sane person is going to stress a knife like this unless it was life or death. Even the most stressed as far as they took it did not destroy the knife, just made the action worse. Makes sense since the balls would be running over a pitted surface. Probably would be a good bit worse on a knife with a lesser ball count, 17 is quite high IMO.
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I agree. Several hundred pounds without catastrophic failure is a win in my book.

Continuous side loading would lead to other problems like deformation around the pivot holes in the handle and blade failure. I'm not aware of a folder meant to do those tasks, much less do it repeatedly with out damage.
 
shinyedges said:
That's because coldsteel tailors the 'test' to the triad locks advantage. I've had many coldsteel knives, my first was a recon 1 with the ultra lock 8 or 9 years ago. They make a good knife.

They have poor form and biased tests. But hey it's marketing and it sells knives.
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This is 100% true. Those tests are not real world tests and often are just bs. But a great marketing tool because folks will believe anything they see on the internet.
 
shinyedges said:
That's because coldsteel tailors the 'test' to the triad locks advantage. I've had many coldsteel knives, my first was a recon 1 with the ultra lock 8 or 9 years ago. They make a good knife.

They have poor form and biased tests. But hey it's marketing and it sells knives.
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Of course they do ! But at least they do conduct such tests . I would dearly love other companies to do so as well . Looks weak to me that they don't .;)
 
At the end of the day neither system is designed to take perpendicular loads. A folder should be built with enough rigidity that the pivot isn't the only part of that end of the folder that keeps everything rigid and strong. Both systems are used in applications that are far more abusive that a knife opening. Bushings are used as main crankshaft bearings in engines. Roller/ball bearings are used in wheels of automobiles, bikes, motorcycles, you name it. The more rigid the frame of the folder is, not including the pivot, the more load it will take.
 
DocJD said:
Of course they do ! But at least they do conduct such tests . I would dearly love other companies to do so as well . Looks weak to me that they don't .;)
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No doubt, I agree more public testing from knife manufacturers would be amazing. I love watching knife tests, it's a favorite pastime for me! Don't get me wrong I watch the cold steel vids too, I just take it with a grain of salt.
 
The design of the knife matters more than the pivots choice of washers or bearings.

For example If you do the same tests to a zt 0804cf vs a boker urban trapper... The trapper will most certainly bend or break or whatever. As it's a super light use knife with thin liners and a small pivot. Where as the zt is tough and built strong.

But that goes with the fact that you want to use the right Tool for the job. Use a slicer for slicing through food, slicer with the correct steel and heat treatment for cutting abrasive materials like rope or cardboard. A thicker tip for stabbing, and so on and so on. Take for example forged in the fire. They have tests done at the end of the makers making the knives. If they didn't design and heat treat it properly it will break.
 
If you're concerned about strength in the pivot area, look at the design of the pivot and stop pin first. Stresses typical of appropriate hard use will stress those components first. Look at vininull's hard use tests on youtube, and see how blade play develops: it's not because of bearing failure. My favorite vininull moment was when the aluminum handle of a Lionsteel SR deformed, which took the stop pin out of position.
 
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