Ball Bearing Pivots

[Morrow]

Do not turn this thread in to a shit show. Those here to provoke, troll or otherwise be a pain in the ass should walk away.

 

[marthinus]

These thoughts on IKBS "cutting" grooves etc are not new and most makers have worked around the issue and resolved it.

IKBS and similar has been around now for some time. Trial and errors have come and gone and it is here to stay IMO.

 

[JR88FAN]

These thoughts on IKBS "cutting" grooves etc are not new and most makers have worked around the issue and resolved it.

IKBS and similar has been around now for some time. Trial and errors have come and gone and it is here to stay IMO.

That's what I was getting at.

Bearing pivots are not "new" and there have been no reported issues of wear on the frame that I can think of (please correct me if I am wrong)

If those issues do start to appear, it will be interesting to see the amount of use/time required to cause the issue, and then we can all make a solid determination of whether that's something we really need to worry about....

 

[benchwarmer380]

That's what I was getting at.

Bearing pivots are not "new" and there have been no reported issues of wear on the frame that I can think of (please correct me if I am wrong)

If those issues do start to appear, it will be interesting to see the amount of use/time required to cause the issue, and then we can all make a solid determination of whether that's something we really need to worry about....

Ive only heard or read about one instance of this occurring and it was actually located in the thread linked to in post #11.

To paraphrase, the owner used his knife pretty hard and kept the pivot pretty tight. It was still smooth and locked up fine.

An issue or a non-issue, that seems to be the question.

 

[PURPLEDC]

I have never in my life seen a knife fail because of the bearings. I have never seen a KVT knife that the bearings wore past the point an IKBS cold rolled race is formed. The only difference between an IKBS race and a KVT knife is that the wear and that groove are forced into an IKBS knife. Once that race is formed and cold rolled the titanium is work hardened, the bearing is supported fully by that cold rolled work hardened race and the lack of load all prevent any further wear. I really think this topic gets taken to the ends of the earth extremes for no apparent reason.

And if people want to get that extreme about it you could argue that milling the handles for hardened inserts weaken the titanium. If there was a single case of a bearing failure proven in the world of knives in the decades they have been used I would say someone may be on to something. But bearing pivots existed before IKBS. RJ martin had been using needle bearing thrust washers in his folders before IKBS hit mainstream. No one decided to fabricate the "Problem" until knives started marketing bearing systems. And all the wear found In KVT knives ceases at a certain point and you will be left with a cold rolled race just like IKBS. People can worry about it if they want to but If I worried about every potential problem never realized I wouldnt leave my house. And I find that the people who complain about bearings the most have the least experience with them. Potential is not the same thing as probable. And potential is nearly limitless.

As far as it being hard to find makers not using hardened steel inserts? I honestly dont think that has anything to do with avoiding problems with wear. I think it has more to do with streamlining manufacturing. Its more cost effective and easier to mill a pocket for premade thrust bearing race inserts than it would be to cold roll a race into titanium in a production setting. But many custom makers still allow the balls to ride right on the titanium. And I know more than a couple makers who actually changed the way they make their knives simply because they got sick of the "what ifs" and lack of trust in how they do things and simply changed how they do things to avoid all the negativity.

 

[Shorttime]

It would be interesting to try to put it to a test.

Mill out a piece of your handle slab material of choice. Better yet, test a Titanium slab alongside an Aluminum and a steel slab.

Mill them out, drop a bearing in, and add weight to the top, equivalent to the blade of a knife. Doesn't really matter what knife, as long as the three are all weighted the same.

I would imagine a small motor could be connected to a series of levers that work a bit like an old steam locomotive's drive arms. Connect them to the pivot bearings, and let the motor spin the bearings back and forth through 180 degrees or so. Not only would it look really neat (I think), it would provide some relatively reliable data.

Stop the motor after 50,000 open/close cycles, and inspect the three slabs for internal wear. Whichever one shows the least wear is your winner.

Regardless of whether or not that all makes sense, I think there is a larger problem than simply the concern (justified or not! I'm not trying to make a statement about whether or not this is something to worry about....) over "wear through".

The larger problem, I think, is that we don't have a lot of Empirical data, from side-by-side tests in identical conditions, to evaluate performance of various parts and methods of folder construction.

 

[DeadOnTarget]

Worst case, The bearings grove to a point in that there is no longer contact and blade stop opening smoothly. Still a usable knive. Everything has a life expectancy. The belt on my car is driven by steel pullies that wear out my belt, Maybe we should only use chains and sprockets?

 

[JR88FAN]

I have never in my life seen a knife fail because of the bearings. I have never seen a KVT knife that the bearings wore past the point an IKBS cold rolled race is formed. The only difference between an IKBS race and a KVT knife is that the wear and that groove are forced into an IKBS knife. Once that race is formed and cold rolled the titanium is work hardened, the bearing is supported fully by that cold rolled work hardened race and the lack of load all prevent any further wear. I really think this topic gets taken to the ends of the earth extremes for no apparent reason.

And if people want to get that extreme about it you could argue that milling the handles for hardened inserts weaken the titanium. If there was a single case of a bearing failure proven in the world of knives in the decades they have been used I would say someone may be on to something. But bearing pivots existed before IKBS. RJ martin had been using needle bearing thrust washers in his folders before IKBS hit mainstream. No one decided to fabricate the "Problem" until knives started marketing bearing systems. And all the wear found In KVT knives ceases at a certain point and you will be left with a cold rolled race just like IKBS. People can worry about it if they want to but If I worried about every potential problem never realized I wouldnt leave my house. And I find that the people who complain about bearings the most have the least experience with them. Potential is not the same thing as probable. And potential is nearly limitless.

As far as it being hard to find makers not using hardened steel inserts? I honestly dont think that has anything to do with avoiding problems with wear. I think it has more to do with streamlining manufacturing. Its more cost effective and easier to mill a pocket for premade thrust bearing race inserts than it would be to cold roll a race into titanium in a production setting. But many custom makers still allow the balls to ride right on the titanium. And I know more than a couple makers who actually changed the way they make their knives simply because they got sick of the "what ifs" and lack of trust in how they do things and simply changed how they do things to avoid all the negativity.

The problem is, when discussing this issue, there are a lot of "perceived problems" with bearing pivots, but zero actual documented real world issues....

It's like someone always points out "potential" issues and they become real issues in the minds of many, even though non of them have ever come to fruition. It's bias without fact.

I can understand liking a knife to have as few parts as possible, there is something to that, but your use has to justify that requirnment.

Like I said, until I see pivot failure because of bearings, it's a non-issue.

 

[PURPLEDC]

The problem is, when discussing this issue, there are a lot of "perceived problems" with bearing pivots, but zero actual documented real world issues....

It's like someone always points out "potential" issues and they become real issues in the minds of many, even though non of them have ever come to fruition. It's bias without fact.

I can understand liking a knife to have as few parts as possible, there is something to that, but your use has to justify that requirnment.

Like I said, until I see pivot failure because of bearings, it's a non-issue.

I completely agree. Thats my whole point. I have never seen it, neither have the people who keep pushing it as a realized issue. So even if a potential exists for a problem I have to ask and Im sure you are curious too, how much time has to go by without a single known example of verified "bearingtosis" before its accepted that its really not something to worry about? I think if there every was an example of overreacting in this hobby this certainly would be it.

 

[craytab]

I'm fine with my bearing zt knives:thumbup:

 

[stog75]

Without getting all 'engineering' on the matter and constructing a free body diagram of the forces exerted on and by the ball bearing, I dont see much force exerted on and translating thru the ball bearing to the race that would causing substantial accelerated wear to the substrate material, in this case the titanium frame.

The normal force the frame would exert on the bearing would almost be negligible, as i dont see applied forces to the bearing. At most it would be equal to the weight of the bearing itself and 'maybe' the blade . Unless I'm wrong, the only force experienced by the ball bearing would be the force of friction to the point static friction is overcome by the release of potential energy by the detent ball setting the whole thing in motion. Once that happens, static friction is gone and dynamic friction forces take over which are even more negligible. Perhaps repeated cycling (flipping open and close) may induce wear buy only to the surface which above posters mention resultant work hardening (of which I agree) -but not to the extent of plastic deformation of the race leading to blade play.

I may be wrong, and certainly wouldn't be my first time, but that's my $0.02 analysis.
Very interesting topic though--- it's fun to theorize and discuss and as mentioned only time will tell.

 

[Jens Schuetz]

If a blade just moves in and out in a straight fashion ball bearings should be the solution with the least friction and thus less overall wear.
Thing is, that this less wear is concentrated at the small area where the balls meet their cage/track.

Additionally wouldn't sideward forces on the blade be leveraged and push the balls on one side of the pivot upward and the balls on the opposing side downward?

Pushing these points of the balls into their groove in the handle will for sure create more of this focussed wear.
What kind of side forces? Just pushing the thumbstud while opening for or removing an avocado seed for example.


A cool compromise would be cylinder bearings. I'm sure somebody must have done this already?
Instead of balls simply use cylinders. They spread out the load and are more resistant to side forces. Disadvantage of course slightly more friction and maybe that dirt can't just move around them like it would around a ball. Maybe a double row of cylinders with a space in between each pair could solve that. Or how about a double row where each circle of cylinders is offset from the other?
I'm sure this can be optimised even more and some people would buy it

While its all cool, and as others have said rationally one should ask how much wear and does it matter? Probably not judging from the lack of negative feedback from the people who use their expensive ball bearing folders very hard ;-)
Still it would make for a nice straight forward experiment and maybe resulting in a paper in some material science or engineering journal.
I got the time.
Who got the funding?

 

[marthinus]

Here are some tests through a simple google search on what IKBS can withstand.
Standard IKBS prying

[video=youtube;SPA_Qodim00]https://www.youtube.com/watch?v=SPA_Qodim00[/video]

IKBS with a parked car on it.

[video=youtube;4RN4WlSm0c0]https://www.youtube.com/watch?v=4RN4WlSm0c0[/video]


Aditional testing done by Shirogorov.

Meanwhile in Russia…

Hi everyone!

Last week I had an awesome opportunity to visit Shirogorov Brothers Workshop, during the talks about knives, production and knife industry development we came up with an idea to test bearings system used in Shirogorov knives in order to determine clear the advantages of specific bearing systems. I’m glad that I can share the results with the community now.
We selected Flipper 95 as a most popular model and the following bearing system were tested:

- Single-row ball bearing system - SRBBS (Serial Division F95), 17 balls on each side between blade and Ti scales.

- Single-row roller bearing system – SRRBS (Custom Division F95), 17 rollers on each side between blade and Ti scales, without hardened steel washers in Ti plates.

- Double-row roller bearing system - DRRBS (Sergey Shirogorov Custom F95), 27 rollers on each side between blade and Ti scales, with hardened steel washers in Ti plates.

The testing was rather simple and pragmatical – we applied a vertical load* directly to the pivot point of the knife resting on two wooden bars so that the pivot had no support. Load was applied progressively to the certain magnitude, then knife was checked for damages sustained, residual deformations to the parts, changes in the mechanics of the locking and flip.
*all the figures are given both in kilos and lbs.

1. Single-row ball bearing system - SRBBS
- 30 kg / 66 lbs – no changes to the mechanics, no deformations;
- 50 kg / 110 lbs - no changes to the mechanics, blade is centered, no blade play, no visual defects. After the knife was taken apart tiny deformation on the titanium plate made by steel ball of the bearings observed (see on the pic. in black);
- 70 kg / 154 lbs – notable changes in the mechanics when deploying the blade slowly without applying the flip, still no blade play, stronger deformations on the titanium plate observed (see on the pic. in red).

2. Single-row roller bearing system – SRRBS
- 75 kg / 165 lbs – no changes to the mechanics, blade is centered, no blade play, no visual defects. After the knife was taken apart slightly noticeable deformation on the titanium plate made by steel rollers of the bearings observed (see on the pic. in black);
- 100 kg / 220 lbs – no blade play, blade is still perfectly centered, barely audible changes in the mechanics and more noticeable deformations on the titanium plate observed (see on the pic. in red).

3. Double-row roller bearing system - DRRBS
- 60 kg / 132 lbs - no changes to the mechanics, blade is centered, no blade play, no visual defects.
- 100 kg / 220 lbs – no changes to the mechanics, blade is still perfectly centered, no blade play, no residual deformations, no alien sounds in the mechanics work.

For better appreciation of the pressure knives withstood, we shot several pictures of the knife bending under the load for Sergey Shirogorov custom Flipper 95 (S90V, 3,5 mm thick spine, DRRBS):

0 kg / lbs

50 kg / 110 lbs

80 kg / 176 lbs

100 kg / 220 lbs

Here is also a video spot (in Russian only unfortunately, just hope that you can get the general idea of the test from it). And sorry for bad focusing, it was the first time we shot video with this camera.

[video=youtube;UyLudvm3sKY]http://www.youtube.com/watch?v=UyLudvm3sKY[/video]

All the best and a sharp edge,
Dmitry

Further improvement on IKBS by Andre Thorburn and Andre van Heerden.

This is the A3 taken apart:

Andre T experimented with caged bearings back in 2011 but has since gone away from it. Trust me when I say his caged system was already VERY smooth and the knife pictured here is one I have handled on numerous occasions as I know the person who won it.

 

[GatorFlash1]

Great pictures and video. Proves just how strong these pivots are and that unless they are subjected to what I consider folder abuse they work as the designer/manufacturer intended.

What I'd like to see are some pics of folders that experienced pivot failure under normal use. I really don't understand how folks dwell on a problem that doesn't exist in real life.

 

[bodog]

This is one of those times where whether you are OK with something or not no one is forcing anyone else to have faith and buy into something. It's completely ok to be a skeptic just like it's ok to be a believer. There are plenty of options regardless of where you stand.

 

[GatorFlash1]

This is one of those times where whether you are OK with something or not no one is forcing anyone else to have faith and buy into something. It's completely ok to be a skeptic just like it's ok to be a believer. There are plenty of options regardless of where you stand.

I agree it is okay to be a skeptic if there are incidences of lock failure with bearing pivots. I have never seen a report of such an incidence for a knife used for normal activities so I'm not a skeptic.

That is why I think this is much ado about nothing unless we want to discuss hypothetical situations. I think the designers and manufacturers have done a good job of making good bearing knife pivots.

Speaking of hypothetical situations, my science-fiction future knife will not have any pivot to argue and fuss about. It will be a laser beam knife, adjustable for length of cutting beam, and power and width of the cutting beam. It will be powered by a life-time battery and have a built in led light illuminating the object to be cut. It will be voice controlled and available for $9.99 and any place selling knives. It will have a variety of handle materials in all shapes and colors.

What say you about that?

 

[mqqn]

And here I have spent all this time trying to figure out what "shotty" means.........

I tend to agree with Matt and Mr. Weiland on the work hardening of the materials while in use.

I have NEVER had a problem with any bearing-pivot knife that I have owned.

best

mqqn

 

[bodog]

I agree it is okay to be a skeptic if there are incidences of lock failure with bearing pivots. I have never seen a report of such an incidence for a knife used for normal activities so I'm not a skeptic.

That is why I think this is much ado about nothing unless we want to discuss hypothetical situations. I think the designers and manufacturers have done a good job of making good bearing knife pivots.

Speaking of hypothetical situations, my science-fiction future knife will not have any pivot to argue and fuss about. It will be a laser beam knife, adjustable for length of cutting beam, and power and width of the cutting beam. It will be powered by a life-time battery and have a built in led light illuminating the object to me cut. It will be voice controlled and available for $9.99 and any place selling knives. It will have a variety of handle materials in all shapes and colors.

What say you about that?

Personally if I was designing a knife I'd probably put a steel washer in just to make sure I was producing the best that could be produced but if ZT decided not to I'm sure they had a reason. That reason is most likely because they can produce the knife at a lower cost/ higher profit margin with few to no warranty concerns. If a couple get used hard enough to need warranty service the cost of replacing the handles or bearings or whatever would cost the company less than it cost to put steel racers in there. But I'm not KAI so my opinion doesn't matter. Most people seem happy with how they're designed and keep buying their products and that's what KAI cares about. They're not in the business of anything other than making the highest profit possible. That means keeping a bulk of their customers happy while bringing in new customers and disregarding the naysayers, regardless of what they think about what's being produced and regardless if they're right or wrong.

 

[GatorFlash1]

Personally if I was designing a knife I'd probably put a steel washer in just to make sure I was producing the best that could be produced but if ZT decided not to I'm sure they had a reason. That reason is most likely because they can produce the knife at a lower cost/ higher profit margin with few to no warranty concerns. If a couple get used hard enough to need warranty service the cost of replacing the handles or bearings or whatever would cost the company less than it cost to put steel racers in there. But I'm not KAI so my opinion doesn't matter. Most people seem happy with how they're designed and keep buying their products and that's what KAI cares about. They're not in the business of anything other than making the highest profit possible. That means keeping a bulk of their customers happy while bringing in new customers and disregarding the naysayers, regardless of what they think about what's being produced and regardless if they're right or wrong.

Why don't you design and sell such a knife? Let the marketplace decide whether or not the few extra pennies you charge or a steel racer is worth it. I'll put up a few bucks for stock in your LLC. Who knows, you might be the next Chris Reeve or Sal Glasser!

 

[bodog]

Why don't you design and sell such a knife? Let the marketplace decide whether or not the few extra pennies you charge or a steel racer is worth it. I'll put up a few bucks for stock in your LLC. Who knows, you might be the next Chris Reeve or Sal Glasser!

Plenty of makers put steel racers in their bearing pivot knives. Just wait. One day some maker like KAI or Spyderco will start doing it and then everyone will come out of the woodwork saying how much better it is and how crazy it was to go without them, like steel lockbar inserts. For some reason knives were pretty ok without them, until they weren't.