Anyone look into the inside of folding knives on the construction?

[Alan0354]

So, a knife blade has to break in two places before the pivot is a concern for breakage? Could that be why you never see a knife break at the pivot?

Could be, but I am talking about this particular point BECAUSE you cannot judge until you open the knife. The tip and the middle of the knife is easy to judge just by looking at it.

More importantly, this is NOT rocket science. I already have THREE knives with ball bearings that is plenty thick showed in post #104 if you care to read before commenting. It is crappy engineering, people do realize that can be a weak point.

AS I SAID many times, most of the proven rugged knives do NOT use ball bearing, you follow what I am talking?

There are knives that have thick enough on that part shown in post #104, do you follow what I said?

I am picking on this weak point BECAUSE you cannot see it until you buy it and open it, do you follow what I said?

I show you cannot judge by the outer appearance like my Sancut Acumen, that looks thick and tough outside, but only 0.03" in the critical part shown in post #103. Do you read and follow what I said?


Did you watch those torture videos, and look into all the ones that survived? You find out whether those have ball bearings? They praised Cold Steel a lot.....that do NOT use ball bearings. Did you research into that?

 

[Alan0354]

Guys, I repeated many times that this is NOT the most critical part of the folding knife, there are more critical things to look. BUT THIS IS SO FAR THE ONLY PART THAT YOU CANNOT SEE UNTIL YOU BUY IT AND OPEN IT UP.

Of cause there are more critical part, the tip of the knife, the middle of the blade, even the thickness of the steel frame for a liner lock are important.

Also how much the liner lock goes UNDER the bottom of the blade is critical( the liner that move under the blade to lock the blade in position). You want to liner goes farther under the blade to make it harder to slip out and unlock the blade.

Also if you move farther back of the handle, how many support to stabilize the two steel plate in the handle. I've seen knives only use ONE single screw to hold the two sides together.

These are things to look out when buying a knife, BUT except the thickness of that part I talked about, EVERYTHING ELSE CAN BE SEEN JUST BY LOOKING AT THE KNIFE. That's what make what I said here more important because you cannot see it.

 

[Alan0354]

Excellent. You're looking at structure now.

Now, how much force is being exerted on that thin part under reasonable stress (prying a can lid, perhaps)? You have to have a reasonable estimate of that to determine how much force is placed on point (not quite a point, but close enough for our purposes) of each bearing's contact with that area. Once you have that figured, you have to factor that it's reinforced from the other side. While that counter-force is likely not on the same point (that'd be impossible to maintain in real-world production), it's near enough to counter most of that. Unless the metal is brittle (which would be a larger problem for the knife), it's unlikely that metal - being supported from both sides with very small spans between supports, and being supported around with thicker metal - would fail under most reasonable force.

I have been talking about the structure all along with all the drawings and pictures!!!

I don't have the data and not easy to get, that's why I am talking here.

I think I forgot to mention one of the most important thing so far WHY I make a big deal on this. It's the brittleness of the blade. If the steel is NOT brittle, 0.03" thick is PLENTY.

Problem is nobody knows how well the blade is QUENCHED. If it's not done right, it can be brittle. I hate to say being a Chinese, I do NOT trust things from CHINA, they have really BAD attitude from the communist days. They fake, look the other way, sloppy..........They just want to get things out the door. I don't trust their blades BUT I am not willing to pay an arm or a leg. So I look out for these stuffs.

There are so many other things that are sloppy on the knives I have, I am talking about up to $70, not S&W cheap stuffs. 70% of the pivot screw on all my knives CANNOT be tighten, the blade will get stuck if you tighten the screw. You have to back off like 1/2 a turn or so. You know what the do? They use thread lock to keep the screw in place without tightening it!!! I have to work on thinning the G10 cover to get it just right so I can tighten the screw.

Even if I pay a lot, what guaranty the quench is correct? So it's just saver to find those at least 0.05" thick instead of settling with thin ones.

 

[Gerry Seymour]

Could be, but I am talking about this particular point BECAUSE you cannot judge until you open the knife. The tip and the middle of the knife is easy to judge just by looking at it.

More importantly, this is NOT rocket science. I already have THREE knives with ball bearings that is plenty thick showed in post #104 if you care to read before commenting. It is crappy engineering, people do realize that can be a weak point.

AS I SAID many times, most of the proven rugged knives do NOT use ball bearing, you follow what I am talking?

There are knives that have thick enough on that part shown in post #104, do you follow what I said?

I am picking on this weak point BECAUSE you cannot see it until you buy it and open it, do you follow what I said?

I show you cannot judge by the outer appearance like my Sancut Acumen, that looks thick and tough outside, but only 0.03" in the critical part shown in post #103. Do you read and follow what I said?


Did you watch those torture videos, and look into all the ones that survived? You find out whether those have ball bearings? They praised Cold Steel a lot.....that do NOT use ball bearings. Did you research into that?

You're assuming some knives don't use ball bearings for the reasons you suspect. But you don't know that. Another possible explanation is that those bearings are more subject to fouling than a thrust bearing, so they avoid them for that reason. Another is that they make the effort to maintain tighter tolerances and smoother surfaces, so the thrust bearings work well (while they may not otherwise).

You've yet to show any evidence that this is, in fact, a point of likely failure in normal or reasonable use - with or without the ball bearings or thinner area.

 

[Alan0354]

You're assuming some knives don't use ball bearings for the reasons you suspect. But you don't know that. Another possible explanation is that those bearings are more subject to fouling than a thrust bearing, so they avoid them for that reason. Another is that they make the effort to maintain tighter tolerances and smoother surfaces, so the thrust bearings work well (while they may not otherwise).

You've yet to show any evidence that this is, in fact, a point of likely failure in normal or reasonable use - with or without the ball bearings or thinner area.

I searched for thrust bearings, those are all thrust bearings as seen in the many pictures, those are balls fixed into the round brass thing.

OF CAUSE I have no evidence, it's a PREDICTION according to the thickness, I am not going to break my Sancut to prove, just looking at the structure to predict.

Like I clarified, if the blade is NOT brittle, 0.03" is good enough, BUT can you rely on that it's done right and it's not brittle?

Like I said, a lot of the torture test were done on knives with no thrust or ball bearings. Show that doesn't proof anything if they don't break at the pivot point.

 

[jks9199]

I'm not sure what you think you'll need to or be able to pry out of in a car accident. Cars have lots of glass - a knife with a glass break and belt cutter is much more likely to help in that scenario.

If you're looking for reasonable prying (like paint can lids, etc.), some knives will survive that, but it's far from what they're designed for, and it puts most of the pressure at the tip (where it's likely to fail long before the tang-to-handle connection).

For a car crash and breaking glass... use a spring loaded centerpunch. Force is concentrated onto a pin-point, and it doesn't require you to do more than push.

Prying with knives... if the tip doesn't snap, there's a good chance the blade will bend... But, in the crashes I've either personally investigated or reviewed reports on -- damn few (none as far as I recall) involved a self-rescue that needed prying. The Jaws of Life or a Sawz-all... Yeah. But those aren't self-rescue.

 

[tkdroamer]

I have no idea what you are talking about the outside dimension of the whole bearing. Here is my drawing in more detail with a real picture, let me know what you are talking.

This is the drawing:
View attachment 29279


This is a real picture with the label so we can speak on the same page:

View attachment 29280

Let me know what you are talking about.

When both bearings are installed, are they not slightly thicker than the thickness of the knife (or at least flush)? Effectively, the OD of the bearing distributes the load all around the section you have listed as 'outer'.

 

[tkdroamer]

That makes sense. I think my question wasn't clear - I was asking about the basic usability, the ability to open the knife with reasonable force. I'd assume you could more easily (i.e. with less force) move a load on a roller bearing (ball or conical) than on a thrust bearing, just because of the friction involved. Would that be correct?

Correct, with exceptions. There will be more frictional loss with flat surface bearings, but the uniformity of the surface means they can handle massive loads.
There are several applications where wooden bearings are still used. Some environments will destroy metal or alloy bearings prematurely. That is pretty cool to me.

 

[Gerry Seymour]

I searched for thrust bearings, those are all thrust bearings as seen in the many pictures, those are balls fixed into the round brass thing.

OF CAUSE I have no evidence, it's a PREDICTION according to the thickness, I am not going to break my Sancut to prove, just looking at the structure to predict.

Like I clarified, if the blade is NOT brittle, 0.03" is good enough, BUT can you rely on that it's done right and it's not brittle?

Again, your prediction is based on an assumption. As for brittle metal, if it was brittle, it wouldn't do well in other torture tests, so those are a good guide.

Like I said, a lot of the torture test were done on knives with no thrust or ball bearings. Show that doesn't proof anything if they don't break at the pivot point.

As for that, you seem to be saying that what they chose to test is proof that what they didn't choose was not going to survive the test. Which would be an assumption. And a good example of confirmation bias.

 

[tkdroamer]

I searched for thrust bearings, those are all thrust bearings as seen in the many pictures, those are balls fixed into the round brass thing.

OF CAUSE I have no evidence, it's a PREDICTION according to the thickness, I am not going to break my Sancut to prove, just looking at the structure to predict.

Like I clarified, if the blade is NOT brittle, 0.03" is good enough, BUT can you rely on that it's done right and it's not brittle?

Like I said, a lot of the torture test were done on knives with no thrust or ball bearings. Show that doesn't proof anything if they don't break at the pivot point.

Please, do not intentionally break a perfectly good knife.

 

[Alan0354]

When both bearings are installed, are they not slightly thicker than the thickness of the knife (or at least flush)? Effectively, the OD of the bearing distributes the load all around the section you have listed as 'outer'.

No!!! The outer part of the thrust bearings do NOT touch the thin part of the blade. It's the little balls that is in contact of the blade at the RED circle. That's how thrust bearings are. The brass round part ONLY hold the balls together. Also, the brass part is very thin, some knives even use plastic for that.

So all the pressure is on the RED circle.

 

[Alan0354]

Again, your prediction is based on an assumption. As for brittle metal, if it was brittle, it wouldn't do well in other torture tests, so those are a good guide.

As for that, you seem to be saying that what they chose to test is proof that what they didn't choose was not going to survive the test. Which would be an assumption. And a good example of confirmation bias.

I am not talking about definite failure, it's not the most critical part of the knife, the tip is more critical. BUT I want PERFECTION!!!!

I want to find those that are strong all around.....AND there are plenty, it's not that I ask for impossible. I ALREADY found 3 with ball bearings that are plenty thick already. Why do I want to settle when I buy the next one? Besides there are ones without ball bearings, why do I have to accept anything with the slightest potential to have problem?

 

[Alan0354]

When both bearings are installed, are they not slightly thicker than the thickness of the knife (or at least flush)? Effectively, the OD of the bearing distributes the load all around the section you have listed as 'outer'.

If you talk about thrusting(shanking), IF the OD of the thrust bearings are very tight fit to the blade, that MIGHT help a little, But I tell you, they are NOT tightly fit. They literally drops out. A lot of knives use plastic also. But for prying, that does not help at all, the pressure is ALL on the RED circle.

 

[Gerry Seymour]

I am not talking about definite failure, it's not the most critical part of the knife, the tip is more critical. BUT I want PERFECTION!!!!

I want to find those that are strong all around.....AND there are plenty, it's not that I ask for impossible. I ALREADY found 3 with ball bearings that are plenty thick already. Why do I want to settle when I buy the next one? Besides there are ones without ball bearings, why do I have to accept anything with the slightest potential to have problem?

Again, you're talking as if you know this to be a likely point of failure. If that's not the case, you're putting a lot of focus on the wrong things - and you haven't shown anything to suggest this actually is a likely point of failure.

 

[tkdroamer]

If you talk about thrusting(shanking), IF the OD of the thrust bearings are very tight fit to the blade, that MIGHT help a little, But I tell you, they are NOT tightly fit. They literally drops out. A lot of knives use plastic also. But for prying, that does not help at all, the pressure is ALL on the RED circle.

I am not aware of a knife blade made for prying. I still remember the 'beating' I got as a kid when I snapped my dad's favorite filleting knife that was in a piece of wood.

 

[tkdroamer]

No!!! The outer part of the thrust bearings do NOT touch the thin part of the blade. It's the little balls that is in contact of the blade at the RED circle. That's how thrust bearings are. The brass round part ONLY hold the balls together. Also, the brass part is very thin, some knives even use plastic for that.

So all the pressure is on the RED circle.

That would mean the load is on whatever the diameter of the balls would be, not the pin in the middle, assuming the fit is decent.

 

[Alan0354]

I am not aware of a knife blade made for prying. I still remember the 'beating' I got as a kid when I snapped my dad's favorite filleting knife that was in a piece of wood.

Yes, it's NOT meant for prying, I want to have one that can stand up to prying. Car is meant for driving from point A to B, why people want big engine to go from 0-60 in in 4sec? BECAUSE THEY WANT IT!!!

Seems like people never get the point that's what I want, I am NOT asking whether it is necessary, I am asking about the design. It's like keep asking why the person want a car that can go from 0-60 in 4sec!!! That's what the person wants!!!

Ha ha, if it's not for the concern of the roof of the Corvette, I would have bought one even though it only seat 2, can't carry much of anything, not good in gas millage, not that reliable........... I just want it!!!

 

[Alan0354]

That would mean the load is on whatever the diameter of the balls would be, not the pin in the middle, assuming the fit is decent.

That's what I've been talking from the very beginning, that's why I never follow what you are talking. For prying, all the force is on the RED ring of balls only. If you read back all my posts, it's all about that.

The ONLY thing that was in my mind and I FORGOT to mention out loud was that I worry about the blade can be BRITTLE(if they did not quench correctly), 0.03" is to thin to withstand the force if it is brittle. If the blade is quenched correctly, even 0.03" is not going to be a problem. I just don't trust anything from CHINA, so I want it to be thicker like 0.05" or thicker.

I guess I watched too many "Forge In Fire" tv show seeing all the blades cracked because of quenching problem.

 

[tkdroamer]

That's what I've been talking from the very beginning, that's why I never follow what you are talking. For prying, all the force is on the RED ring of balls only. If you read back all my posts, it's all about that.

The ONLY thing that was in my mind and I FORGOT to mention out loud was that I worry about the blade can be BRITTLE(if they did not quench correctly), 0.03" is to thin to withstand the force if it is brittle. If the blade is quenched correctly, even 0.03" is not going to be a problem. I just don't trust anything from CHINA, so I want it to be thicker like 0.05" or thicker.

I guess I watched too many "Forge In Fire" tv show seeing all the blades cracked because of quenching problem.

But I think you are still missing the OD sphere of the bearings. Even though a thrust bearing does not have an outer race, the ball bearings are rolling/resting on something. Effectively, the centerline of the ball would define the OD of the bearings supporting surface.

 

[tkdroamer]

Yes, it's NOT meant for prying, I want to have one that can stand up to prying. Car is meant for driving from point A to B, why people want big engine to go from 0-60 in in 4sec? BECAUSE THEY WANT IT!!!

Seems like people never get the point that's what I want, I am NOT asking whether it is necessary, I am asking about the design. It's like keep asking why the person want a car that can go from 0-60 in 4sec!!! That's what the person wants!!!

Ha ha, if it's not for the concern of the roof of the Corvette, I would have bought one even though it only seat 2, can't carry much of anything, not good in gas millage, not that reliable........... I just want it!!!

Okay, don't harden the blade steel. It will never stay sharp, but it will bend before it breaks.