Ball Bearing Pivots

E

edcjunkie

Joined
Sep 27, 2014
Messages
18
First off this thread will be fairly technical on the basis of knife technologies. This could even be compared to the whole debate on steel lock bar inserts. So to the main point, I'm starting to see a possible fault in the design of ball bearing picked in knives, like KVT or IKBS. It seems that through hard use or extended use over time the ball bearings would grind a groove in the frame of the knife especially if that frame was titanium or non heat-treated steel. This brings me mw to my rational on the topic The standard titanium used in knives is 6Al4V titanium which has a Rockwell hardness of 35-40 depending on the maker Most ball bearings are made of either 440c, 52100, or ceramic, 440c bearings are hardened to 58 Rockwell, 52100 bearings are a little harder at 60 Rockwell, and ceramics are much higher on a whole different scale since it is essentially a rock. Blade steels vary in hardness from high 50's to low 60's. The hardness of all of these pose a problem to me, the small hard contact points of the bearings should and will indent the softer titanium frame eventually wearing the material down and thus creating blade play or rendering the knife useless. There's even a video out there showing bits of titanium grind out of the frame effecting the blade's action. Sure it's a nice feature and all, I mean who doesn't like their knife to fly out easily and smoothly, but I'm not sure if the engineering behind it completely weighed out the pros and cons. Although it may prove no issue to the knife at all, but maybe some of the individuals out there with well used bearing pivot knives or even the Umnumzaan or Sebenza 25 owners at there can chime in as to the ceramic detent ball's effect on the lock. So is there anything you all could add a counter argument or anything? I think I might want to get rid of all my knives with bearings because of this information. . .
 
As far as the kvt system goes, Kai knives are lifetime warranty, so I could care less what happens to it over time....if there is a problem, they will fix it
 
I've had several Zaans and one 25. I suspect that such a knife, subjected to everyday hard use for "many" yrs, could present a problem such as you state.
I love my CRK's...won't be getting rid of them.
 
If you're going to get rid of them, then let me pm you my address. I'll take them as a favor to you and for a nominal fee.

if all you do is flick open and close your knife, I suppose the bearing issue will be a limiting factor. But have you consider other factors that may be more limiting such as the usable life of the blade in use?

I think you need to do a comparison of how much usable life you can get out of the blade compared to the length of time until you start seeing issues with the bearing.

The bearings indenting into the titanium material will only be driven by how tightly compressed the bearings are between the handle and the blade. I doubt you'll tighten it to such a degree that accelerates the bearing issue without first experiencing the binding effect on the opening and closing of the knife.

I imagine that whatever compressive force you place on the bearings will go away in time as it does press in the titanium. At that point, you can tighten down some more but presumably, all that wearing down on the titanium will cause some work hardening to occur on the titanium which will then stabilize the opposing forces.
 
if designed properly and functioning correctly, the bearings should be rolling across the surface and not scribing it
 
Reese Weiland told me the surfaces engaging the bearings will work harden before cutting a track becomes an issue.
 
Some knives have thin steel washers between the ball bearing cage and the handle material. The bearings don't roll on the handle, only on the washer.
 
Yes there may be some wear but as stated in another post how much pressure is being applied to the bearings to cause them to wear that hard. But... Based on your understandable argument against bearing pivots, I do think harden steel washers should be dropped in for the bearings to ride on just for that extra saftey net.
 
Redhills said:
Some knives have thin steel washers between the ball bearing cage and the handle material. The bearings don't roll on the handle, only on the washer.
Click to expand...

This is what DDR does. He was the first to incorporate a hardened steel race for the bearings to ride on.
 
I started a simular thread here..Some good points made here and a lot of bickering as well..its a heated topic ...http://www.bladeforums.com/forums/showthread.php/1315095-Disappointed-by-ZT-560

be careful and be prepared to be picked apart by the ZT fanboy club..
I think ball bearings riding directly on titanium and not on an inserted hardened steel race is a big no-no and design flaw. The whole work hardening thing looks like shotty work and was done when the BB craze first started (although I think BB in knives are still in the infancy stage). Have a good time finding any makers besides ZT that dont incorporate a steel race into the titanium these days because they too have seen it as a potential problem and corrected it.



People get real caught up defending there favorite brand of knife here.....hence my signature......
 
trevitrace said:
Thank goodness the resident engineer showed up.
Click to expand...



I think the biggest problem here is that its an issue of pointing out a potential problem. Where some my see it as a very obvious potential problem, some do not share the same enthusiasm, and choose to express that very candidly...
I think having the insight to fix potential problems is a good thing...
 
I think of knives like wooden pencils. Over time they will wear out, whether it's the blade or mechanicals. While I certainly expect a good bit more life out of a bearing knife than a #2 pencil, I'm prepared to replace it at some point in the future. Meantime I just enjoy the use and maintenance of the blades I own.
 
brandoak said:
I think the biggest problem here is that its an issue of pointing out a potential problem. Where some my see it as a very obvious potential problem, some do not share the same enthusiasm, and choose to express that very candidly...
I think having the insight to fix potential problems is a good thing...
Click to expand...


Having the insight and doing nothing with it is just an utter and abject waste then, right?

Just think, you could be the Willy Wonka of all things knife.
 
Mister X said:
I think of knives like wooden pencils. Over time they will wear out, whether it's the blade or mechanicals. While I certainly expect a good bit more life out of a bearing knife than a #2 pencil, I'm prepared to replace it at some point in the future. Meantime I just enjoy the use and maintenance of the blades I own.
Click to expand...
You make a good point. It seems the outlook on a knife with a bearing pivot is it won't last forever. But if the knife is used it won't last forever. The concern some people seem to have is what happens if my safe queen knife is just flipped over and over, you will have a new blade and new handle with a worn out pivot. IMO a little grease once in a while should keep the bearings lubed and prevent a lot of wear.
 
Forget the engineering crap.

It seems to me that if you are a nervous-twitchy knife owner that continually fusses with open and closing their blade then maybe you should not own a ball bearing knife (or any knife). Get a yo-yo to play around with, or learn how to juggle.

https://www.youtube.com/watch?v=gnuFrtTNUTc
 
Interesting thread.

For the first time I am using a knife with bearings, however it's not KVT or IKBS.

It uses caged ceramic bearings and a ceramic detent ball (so the bearings are spinning on the blade and not the frame)

The blade is CPM-154 at around 60HRC, I know ceramic bearings are much harder then that.....

I guess the only way to see how this all works, or doesn't, is to use these knives as you would any other, and then see where things go over periods of time....

I am sure bearing application in knives wasn't just "slapped" together with zero regard toward longevity issues, so we'll just have to see.

I am sure there are already people out there who have been using IKBS or KVT for a decent amount of time (knives that have been opened thousands of times) and I have yet to really hear of or read any complaints....
 
Gadt said:
You make a good point. It seems the outlook on a knife with a bearing pivot is it won't last forever. But if the knife is used it won't last forever. The concern some people seem to have is what happens if my safe queen knife is just flipped over and over, you will have a new blade and new handle with a worn out pivot. IMO a little grease once in a while should keep the bearings lubed and prevent a lot of wear.
Click to expand...

This is a good point as well.

If it's a safe queen does it matter?

If you use a knife for more then opening envelopes then it will have a functionable lifetime.
It could be 5 years. It could be 25 years, there are so many factors at play here....

The question is, will the mechanism that the blade runs on be the main factor in how long it lasts?
I guess we'll find out...
 
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