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

[Alan0354]

What is a thrust bearings? I only know roller bearings which looks like a cylinder or just ball bearings that is a round ball.

 

[tkdroamer]

As I said, it's different. This is a picture of the typical knife with ball bearings.

View attachment 29263

Let's try this way. Look at the picture. This is a typical knife with ball bearings. You can see the DAYLIGHT between the frame on both sides to the blade. The only part that hold the blade tight is the two ball bearings (labeled BB) on each side of the blade. There is NOTHING else supporting the blade. It is only until the thin part CRACKS then the blade can lean on the side plates of the handle to get support.

I have an arrow pointing at the frame lock. In the picture, I worked on it so it goes way under the blade as shown. A lot of knives are not as good, some engage only like 1/2 way. If the blade starts wobbling after it's broken, it might disengage from the frame lock and collapse onto the hand. This is NOT as forgiving as the car door in your example.

As I said, there are knives that made the critical part thicker, it doesn't take a scientist to do that. I have a few knives that has 0.05" or thicker on that part. It's just pure negligence or stupidity they have that part so thin.



EDIT: If you look at the frame lock part of the knife, it has to be quite precise. Notice the bottom of the blade where it touches the frame lock, it is SLANTED. It only works if everything is quite precise and no slack. If the blade start wobbling, it might create a gap in between the blade and the frame lock, the blade can be freed up to close onto the person's hand. It's NOT very forgiving.

That is more the open design of the knife than anything else. Most knives cover up much of the area in your photo. More importantly, look how big the bearing cross section is. That is what is carrying the load. It is Huge compared to the center hole.

Of course, it is the thin section that cracks. This will be consistently true unless there is a bad area in the steel. The same thing is true even if it was on thrust washers. There has to be some clearance.

 

[Alan0354]

That is more the open design of the knife than anything else. Most knives cover up much of the area in your photo. More importantly, look how big the bearing cross section is. That is what is carrying the load. It is Huge compared to the center hole.

Of course, it is the thin section that cracks. This will be consistently true unless there is a bad area in the steel. The same thing is true even if it was on thrust washers. There has to be some clearance.

I don't know what is "open" design. I can assure you MOST if not ALL folding knives look like that. I have more than 10 myself from different brands, this is a good representative of how it looks.

The bearings diameter is NOT a lot bigger than the center hole.

This is the picture of Sencut Acumen, you can clearly see the diameter of the ball bearings vs the center hole. In fact, you can see the ball bearing track mark on the black blade. All the ball bearings I saw look very similar, I can show you more pictures of other brand if you want.

I really don't follow what you said, I don't think we are talking on the same page.

 

[Alan0354]

Guys, this is NOT something I discover, They know about it. There are few that are thick in that part. Here are the pictures of 3 of mine that are thick:

Off-Grid Baby Rhino with thickness of 0.073":

Kubey Dugo KU159 with thickness of 0.063":

This is Laurisilva with thickness of 0.053":

This is NOT rocket science!!! It is EASY to design to have enough thickness, no need of super engineers!!! People are just CARELESS or don't give a crab. How can those stupid people let it go with only 0.03"?!!!

 

[tkdroamer]

I don't know what is "open" design. I can assure you MOST if not ALL folding knives look like that. I have more than 10 myself from different brands, this is a good representative of how it looks.

The bearings diameter is NOT a lot bigger than the center hole.
View attachment 29265

This is the picture of Sencut Acumen, you can clearly see the diameter of the ball bearings vs the center hole. In fact, you can see the ball bearing track mark on the black blade. All the ball bearings I saw look very similar, I can show you more pictures of other brand if you want.

I really don't follow what you said, I don't think we are talking on the same page.

You must be looking at the ID of the bearing. Look at it from the OD.

 

[Alan0354]

You must be looking at the ID of the bearing. Look at it from the OD.

I have no idea how all your questions and comments has anything to do with what I said, you need to describe in more detail what you mean and what your concerns are.

I think I made it as simple as I can explaining with pictures and descriptions. Treat me as simple person, elaborate more. I don't have a high degree, I go by common sense and instincts.

 

[jks9199]

Nobody's going to convince you. Amazingly enough, things aren't designed around being used improperly; they're designed for use in the way they're intended to be used. Cars are not made to survive being dropped on their roofs; they're designed to handle impacts in the relatively normal lines that they'll encounter. They're also not (generally) designed to drive up walls.

The ball bearing design is widely used. That's a clue that it's not failing often, when the knife is used in a reasonable manner. The tip of a knife can be used as pry-tool or screwdriver -- but it's likely to break the tip off because that's not what it's designed to do.

Use tools in the proper manner; if you abuse them, they'll fail you.

 

[Alan0354]

Nobody's going to convince you. Amazingly enough, things aren't designed around being used improperly; they're designed for use in the way they're intended to be used. Cars are not made to survive being dropped on their roofs; they're designed to handle impacts in the relatively normal lines that they'll encounter. They're also not (generally) designed to drive up walls.

The ball bearing design is widely used. That's a clue that it's not failing often, when the knife is used in a reasonable manner. The tip of a knife can be used as pry-tool or screwdriver -- but it's likely to break the tip off because that's not what it's designed to do.

Use tools in the proper manner; if you abuse them, they'll fail you.

No, it is so important for cars to survive dropping on the roof that it's one of the government SAFETY standard(NHTSA) that has to pass before any car can be sold here. I believe it's at least 3 times the weight of the car. That's why IIHC test it to 5 times the weight.

Any knife can work decently "as designed". It's the ones that can survive better in unexpected but useful ways that shines.

Yes, it's important for knives to be able to pry, most common is in car accident that you have to pry your way out. You don't carry a pry bar with you, likely you have one tool and that tool has to be able to do other task. That's the reason there are plenty of knives with seat belt cutter. And don't tell me you can have a pry bar in the glove compartment. What if you are not driving? What if you are sitting in the back seat? Even if you are driving, what if you cannot reach the glove compartment? You have ONLY ONE tool, you want it to be as versatile as possible. AND YES, there are plenty of knives design for that(supposedly).

One cannot be narrow minded.



Like I stressed, I got a few that are tough enough for prying and all. This is ONLY a discussion of the theory, NOT whether we need it.

 

[Rich Parsons]

No, it is so important for cars to survive dropping on the roof that it's one of the government SAFETY standard(NHTSA) that has to pass before any car can be sold here. I believe it's at least 3 times the weight of the car. That's why IIHC test it to 5 times the weight.

Any knife can work decently "as designed". It's the ones that can survive better in unexpected but useful ways that shines.

Yes, it's important for knives to be able to pry, most common is in car accident that you have to pry your way out. You don't carry a pry bar with you, likely you have one tool and that tool has to be able to do other task. That's the reason there are plenty of knives with seat belt cutter. And don't tell me you can have a pry bar in the glove compartment. What if you are not driving? What if you are sitting in the back seat? Even if you are driving, what if you cannot reach the glove compartment? You have ONLY ONE tool, you want it to be as versatile as possible. AND YES, there are plenty of knives design for that(supposedly).

One cannot be narrow minded.



Like I stressed, I got a few that are tough enough for prying and all. This is ONLY a discussion of the theory, NOT whether we need it.

Hi Alan,

https://www.nhtsa.gov/sites/nhtsa.gov/files/fmvss/Roof_Crush_Final_Rule.pdf

From the article and Federal Document above

"Executive Summary a. Final rule As part of a comprehensive plan for reducing the serious risk of rollover crashes and the risk of death and serious injury in those crashes, this final rule upgrades Federal Motor Vehicle Safety Standard (FMVSS) No. 216, Roof Crush Resistance. For the vehicles currently subject to the standard, passenger cars and multipurpose passenger vehicles, trucks and buses with a GVWR of 2,722 kilograms (6,000 pounds) or less, the rule doubles the amount of force the vehicle’s roof structure must withstand in the specified test, from 1.5 times the vehicle’s unloaded weight to 3.0 times the vehicle’s unloaded weight. The rule also extends the applicability of the standard so that it will also apply to vehicles with a GVWR greater than 2,722 kilograms (6,000 pounds), but not greater than 4,536 kilograms 6 (10,000 pounds), establishing a force requirement of 1.5 times the vehicle’s unloaded weight for these heavier vehicles."

It is required to be between 1.5 to 3 times.
And 1.5 times for the those above 6000 lbs and below 10000 lbs.

A further part of the same section has the following quote:

"While this rulemaking action to improve roof strength is part of our comprehensive plan for addressing the serious problem of rollover crashes, this action, by itself, addresses a relatively small subset of that problem. There are more than 10,000 fatalities in rollover crashes each year. To address that problem, our comprehensive plan includes actions to (1) reduce the occurrence of rollovers, (2) mitigate ejection, and (3) enhance occupant protection when rollovers occur (improved roof crush resistance is included in this third category). Our analysis shows that of the more than 10,000 fatalities that occur in rollover crashes each year, roof strength is relevant to only about seven percent (about 667) of those fatalities. We estimate that today’s rule will prevent 135 of those 667 fatalities."


and then

"The portions of our comprehensive plan that will have the highest life-saving benefits are the ones to reduce the occurrence of rollovers (prevention) and to mitigate ejection (occupant containment). We estimate that by preventing rollovers, electronic stability control (ESC) will reduce the more than 10,000 fatalities that occur in rollover crashes each year by 4,200 to 5,500 fatalities (and also provide significant additional life-saving benefits by preventing other types of crashes). In the area of mitigating ejection, significant life-benefits are and/or will occur by our continuing efforts to increase seat belt use and our upcoming rulemaking on ejection 8 mitigation. A more complete discussion of our comprehensive plan is discussed later in this document."

The concentration on testing and directions for improvement are in the areas where more deaths occur.
About 42% to 55%
Which is roll over events.

 

[Alan0354]

Ha ha, I am a lot more familiar about car safety than knives!!!

The original intention of this thread is resolved already, I got my knives that is very tough already. We are just talking theory at this point. Talking about car safety is just as good!!!

Actually the strong roof is a whole lot more important than people realize. It is NOT just about strong roof to protect occupants on roll over. It strengthen the safety on other collisions of a car. To have a strong roof, you have to have strong A-pillars and B-pillars. That is very important for safety on side collision. Those two pillars are just as important as the cross beam inside the door for side impact(remember, the strong door has to link to something strong to hold the door in place). Also, the A-pillar with a rigid roof form the two anchor point for front collision. Remember most cars are unit body, the whole front of the car(with the engine) is linked to the passenger compartment by two big rail under the two front doors AND the two A-pillars. THAT'S IT!!! The two A-pillars ARE like two of the legs of a 4 legs table. People don't realize how important the A-pillars and the roof in head-on or offset front end collision safety.

That's the reason I would never buy a convertible car no matter what. You lose two legs of the table, you can never strengthen the lower two rails enough to make up losing the two A-pillars. I would have bought a Corvette long time ago if not for that. Also a true convertible loses the two B-pillars also( Corvette do have the roll bar in place of the B-pillar.).

When I buy cars, safety is the FIRST and the most important thing I consider.....Over reliability and everything else.

 

[tkdroamer]

I have no idea how all your questions and comments has anything to do with what I said, you need to describe in more detail what you mean and what your concerns are.

I think I made it as simple as I can explaining with pictures and descriptions. Treat me as simple person, elaborate more. I don't have a high degree, I go by common sense and instincts.

You are looking at the INSIDE DIMENSION of the hole for the pin instead of the OUTSIDE DIMENSION of the whole bearing.

 

[tkdroamer]

No, it is so important for cars to survive dropping on the roof that it's one of the government SAFETY standard(NHTSA) that has to pass before any car can be sold here. I believe it's at least 3 times the weight of the car. That's why IIHC test it to 5 times the weight.

Any knife can work decently "as designed". It's the ones that can survive better in unexpected but useful ways that shines.

Yes, it's important for knives to be able to pry, most common is in car accident that you have to pry your way out. You don't carry a pry bar with you, likely you have one tool and that tool has to be able to do other task. That's the reason there are plenty of knives with seat belt cutter. And don't tell me you can have a pry bar in the glove compartment. What if you are not driving? What if you are sitting in the back seat? Even if you are driving, what if you cannot reach the glove compartment? You have ONLY ONE tool, you want it to be as versatile as possible. AND YES, there are plenty of knives design for that(supposedly).

One cannot be narrow minded.



Like I stressed, I got a few that are tough enough for prying and all. This is ONLY a discussion of the theory, NOT whether we need it.

What if a frog had a clutch? It would not jump.

 

[Gerry Seymour]

Let me show another picture of the knife that actually has very thin part, the Sencut Acumen. The thickness is only 0.03". Look at the gap between the side and the blade on both sides are WIDER than the one in the last post.
View attachment 29264

Look at it, there is NOT SUPPORT of the blade other than the ball bearings on both sides.....until it cracks. Also, notice the frame lock metal is NOT as thick as the other one, it can easily slip if the blade start to wobble.

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.

 

[Gerry Seymour]

A bearing will move more freely under the load a knife would typically see, assuming as you say the connection or assembly is correct.
The heaviest recording moving (not rolling) loads are on thrust bearings (flat bearings, aka washers).
It is amazing the variation in bearing quality. Two bearings can have the exact same numbers stamped on them and the life cycle and load they can handle be very different.

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?

 

[Gerry Seymour]

Guys, this is NOT something I discover, They know about it. There are few that are thick in that part. Here are the pictures of 3 of mine that are thick:

Off-Grid Baby Rhino with thickness of 0.073":
View attachment 29266


Kubey Dugo KU159 with thickness of 0.063":
View attachment 29267

This is Laurisilva with thickness of 0.053":
View attachment 29268


This is NOT rocket science!!! It is EASY to design to have enough thickness, no need of super engineers!!! People are just CARELESS or don't give a crab. How can those stupid people let it go with only 0.03"?!!!

You refer to "enough thickness" - for what force? This goes back to my comment a few minutes ago that you'd need to know the forces involved (and include that the area in question is supported on both sides and has thicker material surrounding it) to know what thickness is necessary with a given material.

It's entirely possible that different knives use different thicknesses for reasons other than what you're supposing. A few that come to mind: differences in material, differences in tolerances (design or production parameters), type of bearing (more balls or thrust bearing), more surrounding material, size of gap, etc.

 

[Gerry Seymour]

No, it is so important for cars to survive dropping on the roof that it's one of the government SAFETY standard(NHTSA) that has to pass before any car can be sold here. I believe it's at least 3 times the weight of the car. That's why IIHC test it to 5 times the weight.

Any knife can work decently "as designed". It's the ones that can survive better in unexpected but useful ways that shines.

Yes, it's important for knives to be able to pry, most common is in car accident that you have to pry your way out. You don't carry a pry bar with you, likely you have one tool and that tool has to be able to do other task. That's the reason there are plenty of knives with seat belt cutter. And don't tell me you can have a pry bar in the glove compartment. What if you are not driving? What if you are sitting in the back seat? Even if you are driving, what if you cannot reach the glove compartment? You have ONLY ONE tool, you want it to be as versatile as possible. AND YES, there are plenty of knives design for that(supposedly).

One cannot be narrow minded.



Like I stressed, I got a few that are tough enough for prying and all. This is ONLY a discussion of the theory, NOT whether we need it.

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).

 

[frank raud]

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.

It's almost like knives break at the tip or the middle of the blade. But then real world examples are apparently not common sense.

 

[Alan0354]

It's almost like knives break at the tip or the middle of the blade. But then real world examples are apparently not common sense.

How many times I STRESSED the tip of the blade is the most critical? Then if the tip is fat, you move down to the next weak point and the next. You read the thread?

There are plenty knives with robust pivot point, I ALREADY found all the knives I needed, this is just talking at this point.

If you even care to look for torture and look at what knives they tested, MAJORITY of them are WITHOUT ball bearings like Cold Steel etc. There's good reason why the ones with reputation DO NOT use ball bearings.

You use common sense, but you DO NOT blind guess and assume.

 

[frank raud]

How many times I STRESSED the tip of the blade is the most critical? Then if the tip is fat, you move down to the next weak point and the next. You read the thread?

There are plenty knives with robust pivot point, I ALREADY found all the knives I needed, this is just talking at this point.

If you even care to look for torture and look at what knives they tested, MAJORITY of them are WITHOUT ball bearings like Cold Steel etc. There's good reason why the ones with reputation DO NOT use ball bearings.

You use common sense, but you DO NOT blind guess and assume.

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?

 

[Alan0354]

You are looking at the INSIDE DIMENSION of the hole for the pin instead of the OUTSIDE DIMENSION of the whole bearing.

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:

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

Let me know what you are talking about.