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

[Alan0354]

My wife has a master’s in mechanical engineering, so I’ve learned to pay attention to some of this.

OK, this is just talking only about theory. This is what I drew out:

A) I was thinking about what you said. I would agree with you if the support is a FLAT WASHER as shown in Fig. 1. You can see the whole thin section of the blade(RED) is supported by the flat washer (GREEN). Even the blade is thin at that point, it is still very well supported.

B) But look at Fig.2. If it is supported by ball bearings as show in (GREEN) balls. The pressure right a the tip of the ball bearings pointed by (RED) arrow. You see, there is NO SUPPORT in the rest of the area that is very thin. This will not give good support and the pressure is on the thin part of the blade.

See what do you think.


I have to agree, there doesn't seems to be an issue in real life. There is enough knives that has very thin part in that area. It would be better known if it is a common problem. maybe people don't use the knife for prying and all purpose. But to me, I want it to be all-in-one that if heaven forbid I have to cut myself out of a car accident, I might have to pry metal to get out and that's ALL I HAVE. That's why I am not even looking for the best steel blade that has best edge retention, just have to survive one time, but it has to be tough enough to survive that ONE TIME!!!

I think I found my knife already, just talking out of curiosity.




As for argument about putting a pry bar in the glove box, what if I am driving, I cannot reach it. Worst is if I am a passenger at the back seat?!!! It has to be ON ME all the time.

 

[frank raud]

Just think about, the blade is at least 0.11" thick solid, the handle has TWO metal sides each of 0.06" thick sandwiching the blade. You don't need to be an engineer to tell where is the weak point!!! Just common sense.

Can you point to ONE example of a blade breaking at the pivot point? Can you find an example of the tip breaking on a knife, or a blade breaking in half? Where's the weak point? It's just common sense.

 

[drop bear]

Here is the cold steel sr1. One of their cheaper tank knives.

Not sure how much you want a folder to take. But it takes a bit.

 

[Alan0354]

Here is the cold steel sr1. One of their cheaper tank knives.

Not sure how much you want a folder to take. But it takes a bit.

Cold Steel has good knives, my problem is for the life of me, I cannot flip open those knives with thumb tap like this one!! I need the flipper tap on the other side that is flipped by the index finger. I have one knife with thumb tap and I practiced on it, I almost cut myself trying to flip it open.

If I can flip with the thumb, believe me, Cold Steel would be on my list. There are other brands like Gerber and SOG that have thumb tap and they have some good ones too.

This is a video that disassemble the SR1:

Notice it doesn't use ball bearings? A lot of Cold Steel knives don't use ball bearings, so are some other brands that are known for the ruggedness. Like Cold Steel AD10 also. Here are some disassemble videos of Cold Steels that don't use ball bearings:

There MUST be good reason why the ones that are famous for their ruggedness don't use ball bearings.

I went through A LOT of knives disassembly videos AND a lot of pocket knives torturing videos. A lot of the torture videos are on knives without ball bearings. That gives a deceptive impression that the pivot point is not a weak point. That is because a lot of the knives they tortured did not have ball bearings.

 

[Alan0354]

This is the Steel Will Warbot I bought already. This is MY disassembly picture:

This is a very new knife that just came out early this year, there's no video for it. Just look at the thickness of everything and using bronze washere instead of ball bearings. I bet this one can do very well in torture test also.

The liner is solid 0.06" thick cover the whole inside of the knife. Blade is 0.16" thick with wide tip. One thing, it's quite heavy.

I just bought another Steel Will, the Cutjack:

This is the disassemble video:

Also no ball bearings. The Warbot is smooth enough to flip it open with just the index finger hopefully this one too. There's no reason why not.

 

[Alan0354]

I put in different post to avoid making it too long. There's another very important feature of a knife I got to have, it's the long extension at the front of the handle like my two knives:

You see the long extension at the bottom front of the handle(pointed by the RED arrow) that is formed by the flipper tap of the blade. This is very important to protect the hand from the knife being shoved back into the hand when thrusting(shanking). I don't know why people don't stress on this. It would be a disaster if the blade got shoved back into the hand. there goes the tendons!!!

I practice shanking on the heavy bag with a plastic knife, it definitely want to push back into my hand. I don't know why people buy knives that doesn't have or very little of this to protect the hand. That's the other reason I like knives with flipper tap like this.

 

[Alan0354]

This kind of knife is very popular, I would not want to touch this with a 10' pole!!!

There is no protection of the knife from being shoved back into the hand when thrusting. You thrust, hit a bone and you'd be in deep trouble.

You can see the ones I picked all with long flipper tap, much longer than average. That's why, all in all, it's not easy for me to find a knife.

 

[Monkey Turned Wolf]

You thrust, hit a bone and you'd be in deep trouble.

What exactly would be the trouble if you hit a bone?

Also, where are you hitting that you would hit a bone? From my experience, FMA teach the idea that you slash (so no option to thrust into bone) pretty much everywhere but ribs, neck and eyes. My experience with native american knife fighting is the same. So what exactly is your goal here that involves thrusting into the bone and causing an issue?

My assumption would be that you're thrusting when you should be slashing/not properly trained with a knife, but I'm open to accepting different styles teaching something differently to how I've learned it.

 

[Alan0354]

What exactly would be the trouble if you hit a bone?

Also, where are you hitting that you would hit a bone? From my experience, FMA teach the idea that you slash (so no option to thrust into bone) pretty much everywhere but ribs, neck and eyes. My experience with native american knife fighting is the same. So what exactly is your goal here that involves thrusting into the bone and causing an issue?

My assumption would be that you're thrusting when you should be slashing/not properly trained with a knife, but I'm open to accepting different styles teaching something differently to how I've learned it.

I am just saying. I have only been practicing for 2 weeks more seriously, I practice thrusting to the belly and the head, I guess the head has bones. Even aiming for the eye, there's still bone at the back of the eye. Or even the neck, it's very bony.

With the knives I chose, they will mitigate this issue. At least it's not a problem thrusting on the heavy bag.

 

[Monkey Turned Wolf]

I am just saying. I have only been practicing for 2 weeks more seriously, I practice thrusting to the belly and the head, I guess the head has bones. Even aiming for the eye, there's still bone at the back of the eye. Or even the neck, it's very bony.

With the knives I chose, they will mitigate this issue. At least it's not a problem thrusting on the heavy bag.

A heavy bag is different than a person. Re: the head. If you are targeting a soft area, use a thrust. If a hard area, slash. Doesn't matter what type of knife it is, that's pretty much universal. And if stabbing the eye and you get far enough to stab the bone at the end, you can withdraw it. Ideally before you hit that-there's plenty of squishy stuff first to hit then withdraw.

With the neck I agree it's bony. Typically try slashing it. But there are certain areas you can thrust in the neck, effectively. Which is most of the neck honestly, and again if you're not confident, just slash the neck/arteries.

 

[drop bear]

The ti lite is a flipper.

 

[Gyakuto]

You get what you pay for! A folding knife at $40-70 is probably not going to be very robust. I buy folding knives from Italian craftsmen (they seem to be excellent) and would not pay less than £150 ($170, an arbitrary figure but seems to be a good minimum point). But generally, fixed blades are my preference. Big ones!😈

 

[tkdroamer]

OK, this is just talking only about theory. This is what I drew out:

View attachment 29247

A) I was thinking about what you said. I would agree with you if the support is a FLAT WASHER as shown in Fig. 1. You can see the whole thin section of the blade(RED) is supported by the flat washer (GREEN). Even the blade is thin at that point, it is still very well supported.

B) But look at Fig.2. If it is supported by ball bearings as show in (GREEN) balls. The pressure right a the tip of the ball bearings pointed by (RED) arrow. You see, there is NO SUPPORT in the rest of the area that is very thin. This will not give good support and the pressure is on the thin part of the blade.

See what do you think.


I have to agree, there doesn't seems to be an issue in real life. There is enough knives that has very thin part in that area. It would be better known if it is a common problem. maybe people don't use the knife for prying and all purpose. But to me, I want it to be all-in-one that if heaven forbid I have to cut myself out of a car accident, I might have to pry metal to get out and that's ALL I HAVE. That's why I am not even looking for the best steel blade that has best edge retention, just have to survive one time, but it has to be tough enough to survive that ONE TIME!!!

I think I found my knife already, just talking out of curiosity.




As for argument about putting a pry bar in the glove box, what if I am driving, I cannot reach it. Worst is if I am a passenger at the back seat?!!! It has to be ON ME all the time.

Ball bearings do not work that way. They distribute the load unilaterally across all the balls, inside a race that is the opposing shape. It is a more precision point of contact versus a flat washer. Effectively, the bearing carries the load and perpendicular forces, not the shaft or, in this case blade hole.

 

[Gerry Seymour]

Cool. I have an engineering background.

A far more useful and versatile background than many give it credit for.

 

[Dirty Dog]

A far more useful and versatile background than many give it credit for.

As always, that depends. I doubt a background in, say, biomolecular engineering would help much in this discussion...

 

[Gerry Seymour]

As always, that depends. I doubt a background in, say, biomolecular engineering would help much in this discussion...

Certainly. I was more talking about the problem-solving and analysis engineering education seems to focus on. It’s useful well beyond the scope of their discipline.

 

[tkdroamer]

A far more useful and versatile background than many give it credit for.

I was lucky to know what I wanted to do when I was 15 years old. I have a Masters in EE and engineering management, but a lot of my work is around machine building, so I do a lot of ME type stuff.

 

[Alan0354]

I was lucky to know what I wanted to do when I was 15 years old. I have a Masters in EE and engineering management, but a lot of my work is around machine building, so I do a lot of ME type stuff.

I too found my ultimate passion in EE. I was a musician until I was 25, my degree was BioChemistry. Then I found my ultimate passion in electronics. I started from the bottom, promoted to EE, became manager of EE before I retired. Since retirement, I still study and worked on electronics at home. I went back to music electronics designing guitar amps and extreme high end hifi power amps.

I am very involved in mechanical design also because the kind of instruments we design, the mechanical design is every bit affecting the electronics design about the placement, location of all the stuffs.

I find no education, theory is good enough unless one has a good dose of common sense with I found a lot of people don't have even with high education. When I hire engineers or techncians, I really don't put too much in what school they came from or even what experience they had. I gave them a test I made up, mostly simple stuffs that you can do it if you have a good dose of common sense and truly understand the stuffs. In the analog part test, a lot is straight from a book I studied in the first class of analog circuit in a technical school called Heald College. Those are for technicians. You would think and EE should be able to answer that.............WRONG!!! Anyone failed the test, I just cut the interview short and sent them away politely.

My most favorite part of electronics is RF/microwave and electromagnetics. That I can see and predict how the signal move and all that. Even after I retired in 2005, I still spent a few years studying electrromagnetics and antenna until I realize I memory is really going down, that I forget stuffs I studied. I kept very good notes, a lot of times I read back my notes I wrote a few weeks ago, it's like I never seen it before. But then after I follow my notes step by step, I realized I really UNDERSTOOD it!!! And it's like I have no memory of it anymore!!!! It's a scary feeling. I kind of stop studying since and just more to design amplifiers which was what got me into electronics and quit playing music.

Funny the company I worked for before called me back in 2015 to design the next phase of the instrument and I worked as a contractor for a year and half before I really call it a quit. The tax was really bad and because of my income, it hurts my wife's medicare payment, not only paying a lot of tax, it increased the medicare payment!!!! So I really retired since as my wife really want me to quit.

 

[Alan0354]

Ball bearings do not work that way. They distribute the load unilaterally across all the balls, inside a race that is the opposing shape. It is a more precision point of contact versus a flat washer. Effectively, the bearing carries the load and perpendicular forces, not the shaft or, in this case blade hole.

Ball bearings are not the weak link here, We are talking about the thin flat part of the blade that is the weak part. Look at Fig.2 of post #61, The balls only contact to the surface of the metal at a PIN POINT as indicate. The pressure is at a pin point where the ball contact the flat surface, there is no support on the surrounding surface. It is very different from the case drawn in Fig.1 with a flat washer where the force is distribute evenly on the surface of the thin part....which is surrounded by the thick part of the blade.

 

[tkdroamer]

Ball bearings are not the weak link here, We are talking about the thin flat part of the blade that is the weak part. Look at Fig.2 of post #61, The balls only contact to the surface of the metal at a PIN POINT as indicate. The pressure is at a pin point where the ball contact the flat surface, there is no support on the surrounding surface. It is very different from the case drawn in Fig.1 with a flat washer where the force is distribute evenly on the surface of the thin part....which is surrounded by the thick part of the blade.

I have followed the thread. Yes, disassembled there is a thin cross section. But assembled, it is carrying little to none of the load. You don't seem to understand engineered design.
Yes, there could be issues if the knife assembly were to somehow get loose causing undue loading on the thin cross section.

Ball bearings are not the weak link here, We are talking about the thin flat part of the blade that is the weak part. Look at Fig.2 of post #61, The balls only contact to the surface of the metal at a PIN POINT as indicate. The pressure is at a pin point where the ball contact the flat surface, there is no support on the surrounding surface. It is very different from the case drawn in Fig.1 with a flat washer where the force is distribute evenly on the surface of the thin part....which is surrounded by the thick part of the blade.

I have followed the thread.
Yes, disassembled there is a thin cross section. But assembled, little to none of the load would be on the hole section. You do not seem to understand engineered design.
Yes, if the knife assembly were to somehow get loose, it could load the hole's cross section. But that would be akin to operator error wouldn't it?