Ball Bearing pivots actually weaker than PB washers?

Discussion in 'General Knife Discussion' started by Gideons, Dec 23, 2017.

  1. McFeeli

    McFeeli

    Feb 13, 2017
    Are you telling me that I shouldn't hang free weights off my knife's blade? How else is it supposed to get super buff!?
     
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  2. Therom

    Therom

    Nov 13, 2013
    I think it may be “common sense” to thing simpler is stronger
    From a theoretical point of view I would trust washers more than bearings in extreme conditions
    But honestly I don’t think it is an issue for most common EDC/hard use tasks
    IMO most of us will fails before any of those bearings ;)
    I never had an issue with bearings
    I may préfère washers over bearing for being easier to clean but that is all about it
    If you like the knife and if it is properly done either can be good enough
     
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  3. singularity35

    singularity35

    Mar 1, 2010
    Simple question from the OP though. Which is stronger? All that's needed is a qualification, stronger doing what?

    Whether it reflects real world use or not isn't the question but just from an engineering standpoint. Which of the two systems can withstand more lateral stress? Whether it matters or not, again is not the issue. Whether it's important or not to some is also not the issue.
     
  4. DocJD

    DocJD

    Jan 29, 2016
    If it's so dang "simple" , then what is your answer ?o_O (Assuming lateral stress or whatever you like) .
     
  5. shinyedges

    shinyedges Unfaltering Love & Undeviating Will Knifemaker / Craftsman / Service Provider

    Jun 5, 2012
    I don't think even if he said one over the other it would have any more validity than any other opinion.

    Phosphor bronze washers, nylatron, plastic what ever, will have a crush, bend, deformation point. Without testing to find where each fail, it is speculation.

    What we do know is, all perform their task of being a bushing under normal or even extreme use.
     
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  6. Bohica2u

    Bohica2u

    182
    Jul 1, 2001
    My gawd! How is the human race going to survive if we don't have roller bearings in our knives?!
     
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  7. W. Anderson

    W. Anderson Basic Member Basic Member

    Jun 22, 2016
    We at CERN are working on particle magnet pivot technology as we speak.
     
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  8. sharp_edge

    sharp_edge Gold Member Gold Member

    Jul 30, 2015
    I dont know. Each ball in the ball bearings is certainly much stronger than the pb washer and much less prone to deformation. The plastic that holds all balls together, I am not sure but I tend to belive it is also stronger than the pb washer (which is usually thinner). So, this claim of ball bearings being weaker might be just wrong. Has anyone ever seen ball bearings fall apart?

    Is the knife with ball bearing easier to jam up and become gritty? That I tend to believe so. But some clean up and lube should take care of it. And this has nothing to do with being weak.

    Side to side blade play? No- this is definitely not a problem of ball bearings. If anything, knives on washers are much more prone to side to side blade play.
     
  9. Cobalt

    Cobalt Gold Member Gold Member

    Dec 23, 1998
    How do you figure? I'd like to know how a washer with much more contact surface area has more blade play? Although I don't think this is an issue for either system when done correctly, if you were to pick one system for stiffness it would be the washer.
     
  10. Mo2

    Mo2

    Apr 8, 2016
    What's going to be harder? Steel or phosphorus bronze? Most bearing systems run on hardened steel washer on ti sides. Bearings aren't going to just melt. If they are ceramic there is a possibility of issues but if built right shouldn't be an issue.

    It depends on the design of the knife that makes some knives easier to clean regardless of pivot types if you ask me.
    I've got a real steel megalodon 2017 m390 and it's got roller bearings. The purpose of a roller bearing is to reduce rotational friction and support radial and axial loads. The action is different. It's quite unique. Suggest trying some out. I've never tried it but ruike has a model with them also http://www.ruikeknives.com/about-4.html
     
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  11. DocJD

    DocJD

    Jan 29, 2016
    I mostly associate the pivot bearing with knives designed more for the best fast and smooth operation rather than ultra hard use strength . That doesn't mean they couldn't be engineered for a survival , hard use application . Sealed and made more massive , why not ? Not sure there's much market . There are already fixed blades and plenty of washer type folders geared for the hard use /survival interest . Just mulling it over .:rolleyes:
     
  12. Cobalt

    Cobalt Gold Member Gold Member

    Dec 23, 1998
    Melt? at the speed with which someone opens a folder I do not think you need to worry about melt or soft vs hard. Bearing systems move easier, with less friction, hence their use. Bushing systems take heavier loads with more friction, hence their use in suspension systems. Look under your car or truck and the majority of partial rotating/pivoting components have bushings not bearings. The can take much higher loads due to the flat surface area having much larger force distribution. A ball bearing system would likely be destroyed by suspension loads due to high point stresses on the ball bearings.

    Hardness is irrelevant when you have a flat piece against a slab of handle against a blade flat. It is like a sandwich with layers all pressed against each other. A bearing system has bearings with a single point on each ball bearing touching the surface area. Force is much more evenly spread on a bushing than it is a ball bearing system or even cylindrical bearings. Just simple statics. Each ball takes one point load and the overall force is distributed over however many ball bearings you have.

    In a knife's case, I don't think there is much of a difference, but there is no doubt that the load on a bushing is distributed more evenly over it's larger surface area than a ball bearing system.
     
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  13. shinyedges

    shinyedges Unfaltering Love & Undeviating Will Knifemaker / Craftsman / Service Provider

    Jun 5, 2012
    ^ True dat. More contact between the washer and scale/blade.
     
  14. Steely_Gunz

    Steely_Gunz Got the Khukuri fevah Moderator

    May 9, 2002
    I'm just a dumb bunny. I'll admit it. I'm a contractor, not an engineer. My old man has used and abused some form or fashion of Buck 110 (I think he's on his 3rd in 40ish years) doing a very dirty job. Can you believe it....NO washers and NO bearings :eek:

    But being a brash young man (well, youngish) my EDC is generally some sort of ZT sporting some of those newfangled BBs. Cutting, mild digging, etc...no issues at all. No failure, no difficulty cleaning, and no jamming of the action. It just works. I've never given it a care nor even a thought. I just used my knife.

    Now, I may be a dumb bunny, but I have also been known to be crazy like a fox. When I'm on the job and I need to really cut or pry into something hard-core I reach past my folder to a 4-5" fixed blade. Never had the bearings NOR the washers fail on one of those;)

    I think academic discussion on the PB v. Bearings is informative and entertaining, but I also think it's a non-issue. Both are proven to be strong enough for what a folding knife is supposed to do for my needs.
     
  15. Cobalt

    Cobalt Gold Member Gold Member

    Dec 23, 1998
    That pretty much says it all. It is totally irrelevant.
     
  16. shinyedges

    shinyedges Unfaltering Love & Undeviating Will Knifemaker / Craftsman / Service Provider

    Jun 5, 2012
    Nail, meet hammer.
     
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  17. Chefget

    Chefget Gold Member Gold Member

    Nov 2, 1998
  18. DocJD

    DocJD

    Jan 29, 2016
    I sure don't know . I just noticed that the rollers tested stronger than ball . More surface area ?
     
  19. Lapedog

    Lapedog

    Dec 7, 2016
    I never understood the idea of roller pin bearings arranged in a circle around the pivot like that. Because the part of the pin closer to the centre of the pivot will have to roll slower than the part of the same roller pin that is further from the centre of the pivot. That means the part of the pin further from the centre will be dragging since it has to move a further distance in the same ammount of time.

    I’m not a physicist so there is probably some logical fallacy that I am not getting.
     

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