Ball bearing pivot knives, a new opinion from me.

I am not a knife maker or a materials scientist but I do believe that there is a lot of misunderstanding regarding work hardening.

Work hardening is caused by plastic deformation. If there is no plastic deformation then their cannot be any work hardening. "Work" doesn't cause work hardening, plastic deformation does.

Burnishing is plastic deformation. If the bearings are causing burnishing then the surface may be work hardening but only as deep as the material that has been deformed. A lock bar face can also burnish and be work hardened but only the material that has been deformed will be hardened. In these cases that means only the very surface.

Drilling, cutting and shearing can cause some deformation but only on the surface as I understand it. I do not believe that drilling a pivot hole is gonna make any difference in regards to bearings.

Again, this is just some nerdy average guys understanding of it. I am not an expert on this but I do continually see a lot of misunderstanding about what work hardening is.
 
Insipid Moniker said:
You make lots of claims without evidence (I believe many of them are correct, but evidence matters) and discuss loads and speeds without getting into any specifics regarding either. Your discussion about plain bearings and thrust bearings sounds like you went to wikipedia and did a bit of reading, then extrapolated what you thought was important into a few paragraphs that are vague enough to be totally unhelpful.

What constitutes a high load? What constitutes high speed? You talk about static forces, in normal knife use when is static force applied to the bearings in questions, which is what would make that discussion relevant? What about radial and axial forces?
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What constitutes high loads or high speeds is a very grey area. The static forces that matter in a knife in the case of ball bearings is in twisting and side loads. These kinds of forces come into play when people use their knives to pry a bit, cutting heavily , etc. I cannot predict how everyone uses their knives so I make general statements.

BTW, my preamble was from my own head, my education, and experience with bearings from close to 40 years in the mechanical field. I have been an industrial mechanic, automotive and motorcycle mechanic in racing, engineering manager in the design and manufacture of high speed packaging equipment and scientific research equipment. It is not like I don't have direct experience with bearings in all kinds of conditions.

My OP was to follow up on my opinion of ball bearings in knives. I don't have scientific data to support any assertion and therefore I labelled my statements as opinion. Take it or leave it. People keep asking for some "expert" to answer these questions about titanium once and for all. I don't think anyone will accept anybody as an expert here. There will always be arguments and detractors of anything said. I just provide my 2 cents for those who want it.
 
bearfacedkiller said:
I am not a knife maker or a materials scientist but I do believe that there is a lot of misunderstanding regarding work hardening.

Work hardening is caused by plastic deformation. If there is no plastic deformation then their cannot be any work hardening. "Work" doesn't cause work hardening, plastic deformation does.

Burnishing is plastic deformation. If the bearings are causing burnishing then the surface may be work hardening but only as deep as the material that has been deformed. A lock bar face can also burnish and be work hardened but only the material that has been deformed will be hardened. In these cases that means only the very surface.

Drilling, cutting and shearing can cause some deformation but only on the surface as I understand it. I do not believe that drilling a pivot hole is gonna make any difference in regards to bearings.

Again, this is just some nerdy average guys understanding of it. I am not an expert on this but I do continually see a lot of misunderstanding about what work hardening is.
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Quote: Aldebaran
"My OP was to follow up on my opinion of ball bearings in knives. I don't have scientific data to support any assertion and therefore I labelled my statements as opinion. Take it or leave it. People keep asking for some "expert" to answer these questions about titanium once and for all. I don't think anyone will accept anybody as an expert here. There will always be arguments and detractors of anything said. I just provide my 2 cents for those who want it."

Respectfully sir,
The post from bearfacedkiller is pretty much the explanation we (I) needed.
Work hardening being compared to a "plastic" makes perfect sense.

Take that few micron thick layer of hardened material, and it is still "floating" on top of a softer substrate.
That explains why Carbidizing is needed. To add a thicker layer of harder material.
It also explains why a "work hardened" surface is not the complete answer to a tough/strong/long wearing assembly.

Aside from the few tomatoes, and cabbages thrown... I learned a few things from your post sir.
Thank you!

Thanks for your input Mr. bearfacedkiller!
 
Sorry, I didn't stop to think that "brinelling" maybe wasn't that well a known word and concept here. I used one word in the original post for the concept whereas it might have needed more explanation. bearfacedkiller explained things very well.
 
Brinelling
Brinelling is the permanent indentation of a hard surface. It is named after the Brinell scale of hardness, in which a small ball is pushed against a hard surface at a preset level of force, and the depth and diameter of the mark indicates the Brinell hardness of the surface.

I did not know this...
"The curve is steep but the summit is clear." (that guy that fell off that mountain, somewhere)
 
Aldebaran, you might have all those "40+ years" background knowledge but that doesn't remove the fact that you didn't really put a lot of concrete evidences into play here.

1. You did not use a single knife for a set period of time, say 10 years of hard constant use and then show the result against a control group.
2. You created a hypothesis but then did not follow through with a control group and a variable group to prove said opinionated hypothesis.
3. You used knives you recently bought and put to "moderate" use. That itself is not a scientific process with unbiased results.

I could keep on going but whether your opinions of the matter is valid or not is besides the point. To most of us here, you shot yourself in your own foot constantly by not being able to back it up with rigorous experiments. Want to know a good example of a rigorous experiment? A person taking a busse knife and record his process in breaking that busse knife which took him a long time. And that is just for backyard science experiments.

Lastly, I'm fairly sure the companies that created all those bearings of any sorts did their own rigorous testing far more than you ever did in you alleged 40 years in your mechanical field. After all, there is no quicker way to losing the trust of customers if their products fails after "moderate" use.
 
Ummmm, what does "opinion" mean to you? Did I not say that it was opinion and not a scientific test? I certainly would like to do a scientific test but I only have so much time to spend and doing science on ball bearings in knives is not high on the list of priorities. If I wanted to prove or disprove something I would do empirical science. I said, and again, so there is no doubt, "opinion". It is anecdotal evidence, nothing more. Take it or leave it.

Oh yes, I said almost 40 years, not 40+.
 
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What the hell people...
The fella stated an OPINION!!! Leave it at that!

Nothing constructive is gained by debating the OP on whether he is a NASA engineer or a frigin baseball coach!

If your OPINION differs? STATE THAT!
I'm new here, and I don't see any point in PAYING to read this crap in every other thread!
 
Side to side forces is what may cause an issue. In 99% of pocket knives the side to side forces most people will put on a pocket knife through its lifetime is extremely low and will never cause any issues. Ceramic will certainly cause dimples in ti or steel if it has the ability to. They can also shatter if an extreme force happens to them. The likelihood of that happening in a pocket knife is low. Ceramic causing Divots and also cracking is something that happens in other applications.... You rarely if ever would see it in a pocket knife. But then again there are some pretty low grade materials out there too.

Remember fixed blades are a thing for harder tasks. But even so... If you unlock your pocket knife blade and baton with it, it may survive without issues as long as the steel holds up from the forces. but the pivot and bearing won't be affected. If you used side to side forces to remove the blade from wood it wouldn't be much as the wood would have to be small in diameter to begin with. It wouldn't hurt it.

If you want to pry, get a pry bar. Even then prying forces are going to be so low its not going to do much. The blade would likely snap before anything in the pivot.
 
Mo2, I did say "Folders are not the best use for survival situations and fixed blades are not the best for fun factor at the desk. There are (also) always compromises. Always."
 
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bearfacedkiller said:
I am not a knife maker or a materials scientist but I do believe that there is a lot of misunderstanding regarding work hardening.

Work hardening is caused by plastic deformation. If there is no plastic deformation then their cannot be any work hardening. "Work" doesn't cause work hardening, plastic deformation does.

Burnishing is plastic deformation. If the bearings are causing burnishing then the surface may be work hardening but only as deep as the material that has been deformed. A lock bar face can also burnish and be work hardened but only the material that has been deformed will be hardened. In these cases that means only the very surface.

Drilling, cutting and shearing can cause some deformation but only on the surface as I understand it. I do not believe that drilling a pivot hole is gonna make any difference in regards to bearings.

Again, this is just some nerdy average guys understanding of it. I am not an expert on this but I do continually see a lot of misunderstanding about what work hardening is.
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Thank you, bearfacedkiller.
I am curious to know if someone can tell us whether work hardening occurs at the pivot and the lock face. And if so how deep can it go? I also read that heat also affect work hardening.
I know some knife makers use bearings against Ti scales directly without washers. I also know that some makers do not carbidize or carburize the Ti lock surface (or at least they claim so). Could this be because they know that the Ti surfaces are work hardened enough?

I now remember reading that bearing wear on ti scales would stop at some point because work hardened Ti would surround balls in the tracks.
 
Blues Bender said:
Are you writing a thesis or a review?

Can you provide us with a premise in 4 sentences or less? I'm having a hard time following a 10,000 word post.
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YEAH,! We dont care about your proof or education or any pictures you may have proving your point! We just want to berate you and call you names. Bearing knives are the bomb! My buddy had one in Iran and my other buddy had one in Iraq and they had no problems. And yeah, lets get some second rate wannabe knife maker in here to prove you wrong too...who cares if Ken Onion or any real knife makers have been quoted saying that bearing knives (especially riding on titanium) are inferior......your wrong and you know it! :D
 
shinyedges said:
This has been asked many times of the people who bring up how soft titanium is, can you provide any evidence or do you have an experience with a ball bearing knife that has worn the titanium out of tolerances? Do you realize how many ball bearing knives are out there being used for years now?

I think your preconceived bias taints your ability to see that your "conclusion" is a non issue as it hasn't occurred. They didn't come out last week.

Finally, the forces strong enough to cause permanent dimpling in titanium will likely cause other issues and or break a knife with or with out ball bearings. Remember, we are talking about FOLDING knives.
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Well, shiny, I guess my questions went unanswered. Shrug. 10s of thousands of ball bearing knives functioning as designed for years on end, apparently will wear out any second. This is the largest knife forum in the world and the lack of user reports of ball bearing knives wearing titanium out of tolerance means nothing? Hmm.. peculiar.
 
Zombie411 said:

It worked well enough for Harley, Indian, and Triumph...
It has to work for a knife.
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Ha,ha,ha
I have absolutely nothing constructive to add to this conversation but :
My grail just happens to be a light use knife with ball bearings. I would be fine if it had bronze washers (maybe not Teflon but we won't open that bucket of _______).

One of my machinist friends (who puts many, many more miles on his motorcycle ever year than on his car) . . . back when he road Harleys used to convert the blocks to oil wedge sleeve bearings. Last I saw him, years ago, he was riding a modern Triumph I'm assuming it has the same OWSBs.

. . . to be fair the engines don't have so much static loads and certainly not the same loading as a knife that is being pried with would have to endure. . . . you know . . . prying the hat off a pimp to get your wallet back.

. . . that's what the arrow was about right ? ? ? ? :D :D :D
Blues you're getting to be such a grumpy old bastard. And you're not even old.
. . . better to leave that to us "experts" who are actually OLD and BASTARDS. :)
 
I do get both sides of the argument.
After all it is just a knife that is being discussed.

What I believe in my heart is that these modern / hi dollar knives are made because they are cool. They are fun to flip/close. They are impressive to look at. They make money for the manufacturers, and retailers.

They are not a better tool. I don't believe they were ever intended to be tools. IMHO they are show pieces/play toys for guys that like wearing band aids.

If you have enough money you can drive a Tesla in the woods. That fact does not make a Tesla an off road demon.
If you have enough money you can baton with a ZT top of the line knife. That fact does not make ZT a wood splitting champ.
Just MY 2 cents...
 
Aldebaran said:
My OP was to follow up on my opinion of ball bearings in knives. I don't have scientific data to support any assertion and therefore I labelled my statements as opinion. Take it or leave it. People keep asking for some "expert" to answer these questions about titanium once and for all.. . . . . I just provide my 2 cents for those who want it.
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Yes and THANK YOU for posting it. I'm not big into this obviously but I enjoy reading posts such as yours . . . I have armed my self with a couch, pillows, a pot of coffee and a brilliant stereo with full remote capability . . . I won't be leaving this spot anytime soon and so am quite happy to enjoy your post to the hilt and take my time doing it.

Again thank you.

I don't think anyone will accept anybody as an expert here
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Well no . . . I know I won't. Experts ! HA !
What do they know !
After all they spend all their time fooling around with all those nitty gritty details of knives and knife making.
They're too gritty.
Gritty people they are.
And they have nitts.

There will always be arguments
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With any luck.
 
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