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

[Alan0354]

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.

I still don't know what you are talking exactly, you talking about the OD of EACH or the small little balls that are rolling around in the RED circle?

If that's the case, I don't agree. The ball only TOUCH the flat surface at a PIN POINT, it's a point contact, OD of the little ball has very little to do with in.

 

[Alan0354]

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

NO, it is very basic knowledge for anyone into knives that the two character of steel can not co-exist, either you get edge retention, or you get toughness. For edge, you need HARD steel, but you loses toughness, you want toughness, you loses edge retention. There are ones in around HRC 59-61 like D2 or 9Cr18MoV that has reasonable edge retention and not that brittle. Those knives are in the range of $40 to $100.

That's why I stay in the range of $40 to $80. I don't go for expensive ones, not only they use steel for edge retention, something about the expensive ones that they are just NOT designed for self defense, more for showing off and looks different. Knives like from Spyderco is dangerous for thrusting as there's nothing to stop the knife from being shoved back into the hand like this:
S™ - Spyderco, Inc.

Too bad Cold Steel don't have flipper tap on the blade that I want. It's a good compromise of price and durability. Looks like Steel Will is the main brand for me.

Like I said, I am NOT looking for advice what to buy, I ALREADY have quite a few that are sturdy, D2 or 9Cr18Mov with either no ball bearings or with thick enough of the part of concern.

I demand perfection, I bought a second Steel Will, it's Cutjact 3.5" blade. I spent two days working on it, honing the bronze bearing so smooth that the knife open like the ones with ball bearings. Grind the frame lock so it goes deeper into the bottom of the blade so it's safer. I have good knives.

I am talking about theory and whoever still interest, we can talk. How much are you into knives?

 

[Dirty Dog]

NO, it is very basic knowledge for anyone into knives that the two character of steel

Blade steel has four characteristics, not two. This is basic knowledge for anyone into knives.

can not co-exist, either you get edge retention, or you get toughness.

This "impossible" conjoining of hard and tough is, in fact, the purpose of heat treating a blade, especially differential heat treating. It is also one of the primary reasons things like San Mai exist.
But you won't find that in a $40 knife.

For edge, you need HARD steel, but you loses toughness, you want toughness, you loses edge retention. There are ones in around HRC 59-61 like D2 or 9Cr18MoV that has reasonable edge retention and not that brittle. Those knives are in the range of $40 to $100.

Hardness is more a function of the heat treating choices than the material choice. Yes, it is easier to get a higher HRC with more carbon, but if you know what you're about, you can get pretty much any blade material to any HRC.

That's why I stay in the range of $40 to $80. I don't go for expensive ones, not only they use steel for edge retention, something about the expensive ones that they are just NOT designed for self defense, more for showing off and looks different.

This is utter nonsense.

That's not a knife that was designed for self defense?

How about that one? Bear in mind I own and carry both of them and I am quite confident either one would be very effective as a self defense tool.
Of course, I wouldn't want to use either as a pry bar. But that's ok. I have pry bars too.

 

[Alan0354]

Blade steel has four characteristics, not two. This is basic knowledge for anyone into knives.

This "impossible" conjoining of hard and tough is, in fact, the purpose of heat treating a blade, especially differential heat treating. It is also one of the primary reasons things like San Mai exist.
But you won't find that in a $40 knife.


Hardness is more a function of the heat treating choices than the material choice. Yes, it is easier to get a higher HRC with more carbon, but if you know what you're about, you can get pretty much any blade material to any HRC.

This is utter nonsense.
View attachment 29285
That's not a knife that was designed for self defense?

View attachment 29286
How about that one? Bear in mind I own and carry both of them and I am quite confident either one would be very effective as a self defense tool.
Of course, I wouldn't want to use either as a pry bar. But that's ok. I have pry bars too.

I would NOT carry either one of these, there is NO protection from being shoved back into your hand when thrusting. I want ones that look like these:

With long tap sticking out to prevent the knife from being shoved back into the hand.

Those are very strong knives that has much better chance to survive prying for sure. The lower one is with ball bearings.

Of cause heat treat makes the main difference, but the steel composition makes a big difference also. I read a lot of steel for blades, if all heat treatments are equal, they talk about two main types, either optimized for edge retention OR toughness. You cannot have both. Of cause there are many different type of steel in terms of compositions. But you can either optimize for edge retention(hardness) but brittle, or softer type that is tougher and hard to break, but not good in edge retention. I choose D2 or equivalent that is not that hard, but not that brittle. Price is middle of the road also.

 

[Alan0354]

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.

You disagree, but I still have trouble understanding what you are talking about. Maybe you can educate me why.

 

[tkdroamer]

You disagree, but I still have trouble understanding what you are talking about. Maybe you can educate me why.

You misunderstand what I am saying. From the center point of one ball bearing to the center point of the ball bearing on the opposite defines the diameter of a circle. Each ball bearing is part of that circle and work together.
Never is the blade surface resting on only one ball bearing.

 

[Dirty Dog]

I would NOT carry either one of these, there is NO protection from being shoved back into your hand when thrusting. I want ones that look like these:

Certainly there is. I have tested those designs in actual use (not on people) by cutting and thrusting into objects that are much harder to penetrate than a human. Without having any problems with my hand sliding up towards the blade. Maybe you need to work on your grip?

Of cause heat treat makes the main difference, but the steel composition makes a big difference also. I read a lot of steel for blades, if all heat treatments are equal, they talk about two main types, either optimized for edge retention OR toughness.

I read a lot too, but unlike you I apply that reading. I use blades. I make blades. And what you write above is stupid.
Because heat treatments are not equal. The heat treatment is performed with the end goal in mind, and varies accordingly. It's the equivalent of saying all vehicles, whether a tiny econobox city commuter or a long haul cargo hauler, should all have the same engine.

A well made blade is not optimized for edge retention or hardness. The blade, guard, handle materials and shapes, and the heat treatment, are optimized for the intended usage. But that, again, isn't a factor in cheap throw-away knives.

Form follows function. And you can't buy a Yugo and expect it to perform like a Corvette. You seem to struggle with these concepts.

You cannot have both.

In fact, you can. But not for pocket change.

 

[Alan0354]

Certainly there is. I have tested those designs in actual use (not on people) by cutting and thrusting into objects that are much harder to penetrate than a human. Without having any problems with my hand sliding up towards the blade. Maybe you need to work on your grip?

I practice a lot in thrusting on the heavy bag, it does slip if it doesn't have that. Problem is you are NOT supposed to squeeze it tight, you only squeeze on contact just like punching, you suppose to relax until you are about to contact, then you squeeze the fist.

Problem is in the middle of everything, your timing might be off. For punching, it's no big deal, you don't hit as hard. BUT for knife, the knife can be shoved into your hand and you cut tendons and all!!! It's a chance you do NOT want to take.

I actually filed down on my first plastic knife to experiment, it did not shove all the way, BUT it did got pushed in enough it will cut my index finger if it were a real one. I had to buy a new plastic knife.

You ever actually thrust into a heavy bag to practice? You'll find out really fast.

 

[Alan0354]

You misunderstand what I am saying. From the center point of one ball bearing to the center point of the ball bearing on the opposite defines the diameter of a circle. Each ball bearing is part of that circle and work together.
Never is the blade surface resting on only one ball bearing.

I assume that from the start, that's why I drew a RED ring. Read post #84 again. Read the first two sentence, I already assume the force is applied evenly along the WHOLE RED ring without slack if you read my posts carefully. This is common sense!!! That's why I never follow what you said because I already spelled out loud and clear, and when you raise question, I assume it's something else.

Read post #84 again, my concern is the CRITICAL distance in GREEN between the RED circle(which you are talking about the OD of the those balls) to the edge where the blade trasition from thin to thick. If the distance is large enough, the thick part of the blade is not very helpful in strengthen it. The top drawing is very typical with the real thing on all the knives.

 

[Rich Parsons]

I practice a lot in thrusting on the heavy bag, it does slip if it doesn't have that. Problem is you are NOT supposed to squeeze it tight, you only squeeze on contact just like punching, you suppose to relax until you are about to contact, then you squeeze the fist.

Problem is in the middle of everything, your timing might be off. For punching, it's no big deal, you don't hit as hard. BUT for knife, the knife can be shoved into your hand and you cut tendons and all!!! It's a chance you do NOT want to take.

I actually filed down on my first plastic knife to experiment, it did not shove all the way, BUT it did got pushed in enough it will cut my index finger if it were a real one. I had to buy a new plastic knife.

You ever actually thrust into a heavy bag to practice? You'll find out really fast.

Step one:
Buy a Beef Roast
Step two:
Identify a fresh washed pair of jeans you no longer want.
Step three:
Place Roast into Pant leg.
Step four:
Practice Thrusts, stabs, slicing and slashes.

Step five:
Remove Jeans from Roast
Step six:
Review cuts and stabs (* This can be done through out the process *)

Step seven:
When done, get cutting board and finish cutting up roast into pieces and place in crock pot for beef stew or chili or something else.
Little to no waste.
And if others in the household were out during the process then they are no wiser to one's practice.

 

[frank raud]

I practice a lot in thrusting on the heavy bag, it does slip if it doesn't have that. Problem is you are NOT supposed to squeeze it tight, you only squeeze on contact just like punching, you suppose to relax until you are about to contact, then you squeeze the fist.

Uumm, where did you learn to not hold a knife tightly at all times? This goes against what I have been taught by multiple instructors.

 

[Alan0354]

Uumm, where did you learn to not hold a knife tightly at all times? This goes against what I have been taught by multiple instructors.

It's talked on a video from an expert. You should squeeze the knife only at the point of contact and relax the other time. If you squeeze the knife all the time, you slow down, it's like the whole arm is tight and you cannot move as fast. I just apply the same idea as punching that relax the arm and fist to throw the punch, then tighten up at the point of contact.

 

[frank raud]

It's talked on a video from an expert. You should squeeze the knife only at the point of contact and relax the other time. If you squeeze the knife all the time, you slow down, it's like the whole arm is tight and you cannot move as fast. I just apply the same idea as punching that relax the arm and fist to throw the punch, then tighten up at the point of contact.

Which expert?

 

[Alan0354]

Which expert?

You mean you are taught to squeeze the knife tight when thrusting from beginning of the thrust to the end? Doesn't make you slow down as you likely tighten the arm quite a bit if you squeeze the hand. That will really slow down the movement.

I don't remember which video, I watch quite a bit. BUT that's how punching and kicking are. You never keep everything tight, only tighten up at the last moment.

Like I said, I've been practicing punching on the heavy bag for many years, always relax the hand until the point of contact. BUT there are times in the midst of all the movements, I did not squeeze the fist on time when contact. It's no big deal for punching, you might not hit as hard or worst the wrist collapses, no harm no foul. BUT if you do not squeeze the knife on time while you thrust, if there is no protection, the knife will be shoved back into your hand. That would be bad.

Having a knife like this will protect you hand. The flipper tap will catch on your index finger and prevent the knife from being shoved further back even though you make a mistake.

If you have a knife like this, there's nothing to stop the knife from being shoved back into your hand:

 

[Alan0354]

Step one:
Buy a Beef Roast
Step two:
Identify a fresh washed pair of jeans you no longer want.
Step three:
Place Roast into Pant leg.
Step four:
Practice Thrusts, stabs, slicing and slashes.

Step five:
Remove Jeans from Roast
Step six:
Review cuts and stabs (* This can be done through out the process *)

Step seven:
When done, get cutting board and finish cutting up roast into pieces and place in crock pot for beef stew or chili or something else.
Little to no waste.
And if others in the household were out during the process then they are no wiser to one's practice.

Ha ha, do you know how much beef cost now-a-days. The only time I cut beef is on the dinner table!!!!

 

[tkdroamer]

I assume that from the start, that's why I drew a RED ring. Read post #84 again. Read the first two sentence, I already assume the force is applied evenly along the WHOLE RED ring without slack if you read my posts carefully. This is common sense!!! That's why I never follow what you said because I already spelled out loud and clear, and when you raise question, I assume it's something else.

Read post #84 again, my concern is the CRITICAL distance in GREEN between the RED circle(which you are talking about the OD of the those balls) to the edge where the blade trasition from thin to thick. If the distance is large enough, the thick part of the blade is not very helpful in strengthen it. The top drawing is very typical with the real thing on all the knives.

I think I understood most of your drawings. IF the thick part were to create come kind of shoulder that could rest against something under load, it could help. But this would negate our whole premise that the knife is a precision assembly.
If we keep with the premise that the assembly has a tight tolerance, then the thicker section of the blade would not offer any strength. The thinnest cross section is where the blade would likely break, sans the bearing area. This is assuming the greatest load it at the pivot point. Jam the blade in a piece of wood and now you have a different lever (moment) point.

 

[frank raud]

You mean you are taught to squeeze the knife tight when thrusting from beginning of the thrust to the end? Doesn't make you slow down as you likely tighten the arm quite a bit if you squeeze the hand. That will really slow down the movement.

I don't remember which video, I watch quite a bit. BUT that's how punching and kicking are. You never keep everything tight, only tighten up at the last moment.

Like I said, I've been practicing punching on the heavy bag for many years, always relax the hand until the point of contact. BUT there are times in the midst of all the movements, I did not squeeze the fist on time when contact. It's no big deal for punching, you might not hit as hard or worst the wrist collapses, no harm no foul. BUT if you do not squeeze the knife on time while you thrust, if there is no protection, the knife will be shoved back into your hand. That would be bad.

Having a knife like this will protect you hand. The flipper tap will catch on your index finger and prevent the knife from being shoved further back even though you make a mistake.
View attachment 29295


If you have a knife like this, there's nothing to stop the knife from being shoved back into your hand:
View attachment 29296

Aah, the unknown expert. I understand why you remain relaxed while punching, to increase speed( slightly), but that is not necessary with a knife. ANY knife has the potential to slide out of your grip, and possibly cut your fingers, if you hold it loosely. THAT'S common sense.

 

[Dirty Dog]

I practice a lot in thrusting on the heavy bag, it does slip if it doesn't have that.

The knives I posted DO have that. And I have tested them (as have others) and can confirm that they are plenty deep enough to prevent the hand from sliding down onto the blade.

Problem is you are NOT supposed to squeeze it tight, you only squeeze on contact just like punching, you suppose to relax until you are about to contact, then you squeeze the fist.

I know how to use a blade.

Problem is in the middle of everything, your timing might be off. For punching, it's no big deal, you don't hit as hard. BUT for knife, the knife can be shoved into your hand and you cut tendons and all!!! It's a chance you do NOT want to take.

I also know more about hand injuries than you ever will.
It seems clear to me that you're looking for a technological solution to a training problem.

I actually filed down on my first plastic knife to experiment, it did not shove all the way, BUT it did got pushed in enough it will cut my index finger if it were a real one. I had to buy a new plastic knife.

Or, as a better alternative, you could learn how to use the knife properly.

You ever actually thrust into a heavy bag to practice? You'll find out really fast.

Sure. And, with training blades and safety equipment, into humans. Fingers are fine. The problem, Alan, much as you typically don't want to hear it, is you. You don't know how to use the knife properly and are unwilling/unable to learn. So you insist the problem is the knife. It's not.

 

[Alan0354]

I think I understood most of your drawings. IF the thick part were to create come kind of shoulder that could rest against something under load, it could help. But this would negate our whole premise that the knife is a precision assembly.
If we keep with the premise that the assembly has a tight tolerance, then the thicker section of the blade would not offer any strength. The thinnest cross section is where the blade would likely break, sans the bearing area. This is assuming the greatest load it at the pivot point. Jam the blade in a piece of wood and now you have a different lever (moment) point.

I like described in #84, if the critical distance is smaller like the lower diagram, the thicker part might help, but in real knife, it's quite far to be of help. That's why I raise up the concern on the first place.

If you jam the blade in a piece of wood, that's thrusting, I don't think it's that bad even that part is thin.

Bottom line, it's NOT that hard to make that part thicker, this is proven by 3 knives I have that is plenty thick. The only reason I can think of is those people did not think deep enough. It's not rocket science if they just stop and look and think. This is not my discovery of the problem, just discovered how stupid some of them are and they call themselves designers.

Like I said, I already found my knives that is good both with ball bearings and without. More like a discussion or gripping at this point. Problem is solved for me.

 

[Alan0354]

Aah, the unknown expert. I understand why you remain relaxed while punching, to increase speed( slightly), but that is not necessary with a knife. ANY knife has the potential to slide out of your grip, and possibly cut your fingers, if you hold it loosely. THAT'S common sense.

Relaxing increase speed quite a bit. Same as swinging the knife from my few weeks of experience.

How can you grab the knife tight all the time and be fast? Tell me some tricks, I am open to learn. I am confident about the physics and logic part, but I am not expert in knife fighting.

As of right now, unless I learn something different, I rather play it safe and depend on the long flipping tap to protect my hand in case I do not squeeze on time.