New lock mechanism for folder knive

[nhobo]

I don t think that would be problem at all .First , you are talking of forces in opposite way of force we apply when we cutting . Anyway it will me much stronger then liner lock . Pivot can be in this shape / as in the drawing / to fit in frame. Of course , there are many other solutions to prevent the pivot from turning into the frame ,i give just example .Look , I don t want to design stronger lock then Cold Steel Tri-Ad ..................
PS. I'm glad you understood how it would all work

Assume that the area of engagement of a liner lock is comparable to the area of engagement of your double D pivot. The leverage on the liner lock is 1:1, so at 50 lbs the force is 50 lbs. As described above the leverage on your pivot is 12:1, or 600 lbs at the same force. Therefore your pivot lock idea will be not be "much stronger than a liner lock", by this example the liner lock is 12x stronger. Even if the liner lock has only half the engagement of the pivot is is still 6x stronger.

I'm not trying to be a jerk here but what you think doesn't matter. You need to understand the physical forces involved and the properties of the materials you are using. All materials are plastic and flow / deform - just like the edge of a knife. Until you understand these forces you're just spinning your wheels.

Make a double "D" shaped hole in thin steel the thickness of a liner. Solidly weld a shaped key that fits into the hole onto a short length of steel bar. Insert the key in the hole and twist it using the steel bar as a lever. Do this until something breaks.

 

[carnifex knifeworks]

Seems like it would work. To be honest though, it seems like a more complex version of a button lock. However, your design might create better lockup.
Some complaints about button locks are that it can have a little play/slop and the blade can wiggle around.

It does look like it would work and provide a strong lock. It might even have a benefit over a conventional button lock. However, it also looks like your design could have a button protruding above the the scales on the pivot, unless you countersink it deeply enough. If you countersink it that deeply though, the button may not be easily actuated and that area will collect dirt and debris.

I know this wasn't asked, but:
Would it sell? Yes. Some people would buy it because there are collectors that love unique knives. Would it sell very well? Depends on the other aesthetics of the knife, the materials used, and the price point.

 

[VorpelSword]

A lot of inteesting back and forth without drama . . .all good stuff!

So, has this sort of mechanism been used in a folding knife?

 

[Natlek]

Assume that the area of engagement of a liner lock is comparable to the area of engagement of your double D pivot. The leverage on the liner lock is 1:1, so at 50 lbs the force is 50 lbs. As described above the leverage on your pivot is 12:1, or 600 lbs at the same force. Therefore your pivot lock idea will be not be "much stronger than a liner lock", by this example the liner lock is 12x stronger. Even if the liner lock has only half the engagement of the pivot is is still 6x stronger.

I'm not trying to be a jerk here but what you think doesn't matter. You need to understand the physical forces involved and the properties of the materials you are using. All materials are plastic and flow / deform - just like the edge of a knife. Until you understand these forces you're just spinning your wheels.

Make a double "D" shaped hole in thin steel the thickness of a liner. Solidly weld a shaped key that fits into the hole onto a short length of steel bar. Insert the key in the hole and twist it using the steel bar as a lever. Do this until something breaks.

My friend , I fully understand what you are talking about .......thanks for reply .
Liners/frame can be little more thicker than average .As I already say there are many ways to fix pivot in place . I am car mechanic so in my work I see many ways how two part are fixed to not spin . To make all that stronger pivot can be little large in Dia .. then average used pivots in knives Anyway for now I m just loud thinking ....

 

[Natlek]

If anyone still don t understand how it would work ,This is best I can in a hurry

 

[Natlek]

Guys, this is a general idea , I wrote it down here so I don't forget it We can discuss the details further .....

 

[ferider]

Makes the blade quite complicated. Remember, the blade is machined mostly before heat-treat, and during heat-treat, the size can change. Enough that a ball will not precisely fit anymore.

Why not use cylinders instead of balls ? Or for that matter, you can just use a single cylinder ? Gives you more strength against lateral force, too.

 

[Natlek]

Make a double "D" shaped hole in thin steel the thickness of a liner. Solidly weld a shaped key that fits into the hole onto a short length of steel bar. Insert the key in the hole and twist it using the steel bar as a lever. Do this until something breaks.

If I do that on double frame / like on finished knive / and let say they are 2.5 mm thick hardened steel and pivot is double D on one end and 10 mm. Dia , also hardened steel ?
Everything can be break , I think that would be more than enough strong for purpose ....? Again we are talking on down side forces , opposite of normal use of knife . In which scenario there would be applied that much of force to break this 10mm pivot and 2.5mm thick frame from hardened steel ?

 

[Natlek]

Makes the blade quite complicated. Remember, the blade is machined mostly before heat-treat, and during heat-treat, the size can change. Enough that a ball will not precisely fit anymore.

Why not use cylinders instead of balls ? Or for that matter, you can just use a single cylinder ? Give you more strength against lateral force, too.

That is good question ....... holes can be drilled on final dimension after HT ...carbide drill bits and reamers are for that .......?

 

[killgar]

When designing a knife (or knife lock) there are a few questions to answer-

1. Will it work?
2. Is is consistently reliable?

If a person is designing something just for their own amusement and/or satisfaction, and they will be happy with producing one example for personal ownership, then the only limits are how much money and effort they are willing to put into it. And of course, the limits of physics.

But if a person is thinking about mass-production, or even a limited run, then there are other questions to answer along with the first two I mentioned-

1. How much will it cost to produce the parts? Precision machinery and skilled people to manufacture the parts, or the cost to have others manufacture them.

2. How much will it cost to assemble the final product? Time equals money in a production factory. The longer it takes to assemble something, the fewer you can assemble in a day.

3. How difficult is it to assemble? Is it complicated? Will assemblers need special skills or training? Will assembly require special tools, perhaps tools that need to be made (more cost).

4. What will the final, finished product cost the consumer?

5. Is there a demand? Is it a better "mouse trap"? Will people prefer the new design over all the other existing options? Will people be willing to pay whatever the final price is for the new design?

I believe that these are questions that any knife manufacturer would ask themselves when considering using a new lock design.



As far as your specific design, unless I'm missing something, it looks like it's designed so that gravity is what causes the balls to drop out of the blade divots when the button is pressed, with no springs or other design features to force the balls out of the divots during unlocking of the blade (I base this on your diagram and description in post #12). If this is correct, then I see a few problems-

Because there are three balls, and because the balls are positioned around the pivot, if a person tried to unlock the blade by holding the knife with any "edge" of the knife facing up/down, then there would always be at least one ball that would remain in the corresponding blade divot, and the blade would not unlock. The same action of gravity that would cause one ball to drop out of the blade divot (pulling the ball down), would also cause a ball on the other side to be pulled down into the blade divot.

Now if a person held the knife with the sides of the knife facing up/down when they press the lock button, it's possible that all three balls might drop out of all three blade divots, but maybe not (reliability).

This problem might be solved by using only one ball and blade divot instead of three, but then there's this-

If the tolerances between the ball and divots are tight, and they would need to be tight to prevent serious lock-play when the knife is open, then that would increase the chances of one or more balls sticking in the blade divots when attempting to unlock the blade. And then there's oil. Oil could cause one or more balls to stick in the blade divots, especially if the tolerances between the balls and divots are tight.

Also, there is always the question of how susceptible the lock mechanism will be to failure due to crud like dust/dirt/lint/ect getting into the mechanism and causing failure (blade not unlocking). Any opening/gap in a knife, no matter how small or narrow, is going to collect crud if the knife gets carried.


On the other hand, I can see the possibility that by applying pressure to the back of the blade (normal closing of a folder) the blade divots themselves pushing the balls against the edges of the holes in the pivot might force the balls out of the blade divots and into the pivot during unlocking (not having to rely on gravity), but such a lock design would involve some very precise machining, and that brings back the issue of lock-play. Because the balls, pivot, blade divots, and piston all have to work together to keep the blade locked, the machining tolerances would have to be so tight to prevent lock-play that I think it would be cost prohibitive.


In my opinion, I don't think the design would be practical or reliable enough to be feasible. Or at the very least, that production would be cost prohibitive on any kind of scale.

None of this is intended as criticism or discouragement. I'm all in favor of people coming up with new ideas and pursuing their dreams. And it's always possible I could be wrong.

 

[Natlek]

When designing a knife (or knife lock) there are a few questions to answer-

1. Will it work?
2. Is is consistently reliable?

If a person is designing something just for their own amusement and/or satisfaction, and they will be happy with producing one example for personal ownership, then the only limits are how much money and effort they are willing to put into it. And of course, the limits of physics.

But if a person is thinking about mass-production, or even a limited run, then there are other questions to answer along with the first two I mentioned-

1. How much will it cost to produce the parts? Precision machinery and skilled people to manufacture the parts, or the cost to have others manufacture them.

2. How much will it cost to assemble the final product? Time equals money in a production factory. The longer it takes to assemble something, the fewer you can assemble in a day.

3. How difficult is it to assemble? Is it complicated? Will assemblers need special skills or training? Will assembly require special tools, perhaps tools that need to be made (more cost).

4. What will the final, finished product cost the consumer?

5. Is there a demand? Is it a better "mouse trap"? Will people prefer the new design over all the other existing options? Will people be willing to pay whatever the final price is for the new design?

I believe that these are questions that any knife manufacturer would ask themselves when considering using a new lock design.



As far as your specific design, unless I'm missing something, it looks like it's designed so that gravity is what causes the balls to drop out of the blade divots when the button is pressed, with no springs or other design features to force the balls out of the divots during unlocking of the blade (I base this on your diagram and description in post #12). If this is correct, then I see a few problems-

Because there are three balls, and because the balls are positioned around the pivot, if a person tried to unlock the blade by holding the knife with any "edge" of the knife facing up/down, then there would always be at least one ball that would remain in the corresponding blade divot, and the blade would not unlock. The same action of gravity that would cause one ball to drop out of the blade divot (pulling the ball down), would also cause a ball on the other side to be pulled down into the blade divot.

Now if a person held the knife with the sides of the knife facing up/down when they press the lock button, it's possible that all three balls might drop out of all three blade divots, but maybe not (reliability).

This problem might be solved by using only one ball and blade divot instead of three, but then there's this-

If the tolerances between the ball and divots are tight, and they would need to be tight to prevent serious lock-play when the knife is open, then that would increase the chances of one or more balls sticking in the blade divots when attempting to unlock the blade. And then there's oil. Oil could cause one or more balls to stick in the blade divots, especially if the tolerances between the balls and divots are tight.

Also, there is always the question of how susceptible the lock mechanism will be to failure due to crud like dust/dirt/lint/ect getting into the mechanism and causing failure (blade not unlocking). Any opening/gap in a knife, no matter how small or narrow, is going to collect crud if the knife gets carried.


On the other hand, I can see the possibility that by applying pressure to the back of the blade (normal closing of a folder) the blade divots themselves pushing the balls against the edges of the holes in the pivot might force the balls out of the blade divots and into the pivot during unlocking (not having to rely on gravity), but such a lock design would involve some very precise machining, and that brings back the issue of lock-play. Because the balls, pivot, blade divots, and piston all have to work together to keep the blade locked, the machining tolerances would have to be so tight to prevent lock-play that I think it would be cost prohibitive.

THAT WOULD WORK
In my opinion, I don't think the design would be practical or reliable enough to be feasible. Or at the very least, that production would be cost prohibitive on any kind of scale.

None of this is intended as criticism or discouragement. I'm all in favor of people coming up with new ideas and pursuing their dreams. And it's always possible I could be wrong.

Divots in blade should be smaller then half ball so blade will push them in , no matter in which position is knife .That would work nice .
I agree with almost everything you write .
Also , production of parts is easy this days ..... once you set up the machine, it will do thousands pivots in a day.....

 

[Natlek]

it starts to look like something

 

[killgar]

Divots in blade should be smaller then half ball so blade will push them in , no matter in which position is knife .That would work nice .
I agree with almost everything you write .
Also , production of parts is easy this days ..... once you set up the machine, it will do thousands pivots in a day.....

I believe the design could work (blade forcing balls into pivot), but as I mentioned, there are several parts in that lock design that would have to work perfectly together to achieve a tight lock-up. Something that "works" may not be practical or affordable to produce. For example-

If there is any slack between the balls, blade, and piston when the blade is locked, that would produce lock-play.

If there is any slack between the balls and the holes in the pivot when the blade is locked, that would produce lock-play.

If there is any slack between the outer diameter of the piston and the inner diameter of the pivot, that would produce lock-play.

This means that all parts involved in the lock-up would need to be precisely machined and fitted. On a few knives that might be possible, but at a high cost. The problem with machining precision steel parts in numbers is that the cutters wear out fast and need to be replaced, and this becomes expensive. When tight tolerances are not required, cutters might be re-sharpened and re-used, but if you're going for a tight lock-up, and want to avoid all the issues I described regarding slack between parts, then that means frequent replacement of cutters.

By no means am I claiming to be an expert on the machining of parts, but it is my understanding that the first parts made with a new cutter will always be closer to specs than the last parts made with that cutter. This is due to the cutter experiencing microscopic wear during use. I'm sure there are people on this forum who know more about mass-production of machined parts and machining than I do, so please correct me if I'm wrong on anything I've said.

If lock-play were not an issue, then most of what I just posted would not be an issue, but we're talking about a knife, and knife owners tend to be very particular (critical) about lock-play, especially on expensive knives.

In any event, I like the ingenuity of your design, and I think it would be cool if you could produce it. I'm sure it would be very gratifying to produce something new and have it work. I have produced a few simple knife mechanisms myself (nothing as ambitious as your lock, and no mass-production), so I know from experience that such accomplishments can be a great source of pride.

Good luck. I've enjoyed this thread and looking at your design.

 

[Arathol]

Kinda looks like the Axial lock designed by Paul Poehlmann. It was used on the Gerber Paul folders in the 1970s and 80s.

US3942249A - Knife - Google Patents

A knife for personal use has a liner made up of a pair of parallel walls spaced apart along a transverse axis at right angles to the longitudinal extent of the walls. A hollow hub extends along the axis and abuts bearing surfaces in the walls and also abuts a bearing surface in a blade disposed...

patents.google.com

 

[Natlek]

I believe the design could work (blade forcing balls into pivot), but as I mentioned, there are several parts in that lock design that would have to work perfectly together to achieve a tight lock-up. Something that "works" may not be practical or affordable to produce. For example-

If there is any slack between the balls, blade, and piston when the blade is locked, that would produce lock-play.

If there is any slack between the balls and the holes in the pivot when the blade is locked, that would produce lock-play.

If there is any slack between the outer diameter of the piston and the inner diameter of the pivot, that would produce lock-play.

This means that all parts involved in the lock-up would need to be precisely machined and fitted. On a few knives that might be possible, but at a high cost. The problem with machining precision steel parts in numbers is that the cutters wear out fast and need to be replaced, and this becomes expensive. When tight tolerances are not required, cutters might be re-sharpened and re-used, but if you're going for a tight lock-up, and want to avoid all the issues I described regarding slack between parts, then that means frequent replacement of cutters.

By no means am I claiming to be an expert on the machining of parts, but it is my understanding that the first parts made with a new cutter will always be closer to specs than the last parts made with that cutter. This is due to the cutter experiencing microscopic wear during use. I'm sure there are people on this forum who know more about mass-production of machined parts and machining than I do, so please correct me if I'm wrong on anything I've said.

If lock-play were not an issue, then most of what I just posted would not be an issue, but we're talking about a knife, and knife owners tend to be very particular (critical) about lock-play, especially on expensive knives.

In any event, I like the ingenuity of your design, and I think it would be cool if you could produce it. I'm sure it would be very gratifying to produce something new and have it work. I have produced a few simple knife mechanisms myself (nothing as ambitious as your lock, and no mass-production), so I know from experience that such accomplishments can be a great source of pride.

Good luck. I've enjoyed this thread and looking at your design.

IF ............. Tight tolerance are not problem on CNC , and ceramic insert in cutting tools last quite long .
Maybe one ball should be fraction of mm. offset to avoid any possible play ?

 

[Natlek]

In any event, I like the ingenuity of your design, and I think it would be cool if you could produce it. I'm sure it would be very gratifying to produce something new and have it work. I have produced a few simple knife mechanisms myself (nothing as ambitious as your lock, and no mass-production), so I know from experience that such accomplishments can be a great source of pride.

Good luck. I've enjoyed this thread and looking at your design.

Sometimes in chaos in my workshop I find those parts that I mentioned from large hard disks . If I find one I can adapt it very easily for probe . it's already a finished solution, just a little work on lathe . Blade is problem.....
Or , I can ask my friend for help who has every possible CNC , EDM , laser fiber ..... but he will kill me
I will think more about this ....I will make it for sure when I am ready
It was a pleasure talking to you about this .You raise the right questions and issues

 

[Arathol]

The Gerber Paul design solved the lock play problem by using a small screw on the bottom of the knife to adjust for vertical play and a threaded collar for side-to-side play. Once you get it adjusted right it will have zero play and the knife will just fall open when you unlock the blade.

 

[Natlek]

The Gerber Paul design solved the lock play problem by using a small screw on the bottom of the knife to adjust for vertical play and a threaded collar for side-to-side play. Once you get it adjusted right it will have zero play and the knife will just fall open when you unlock the blade.

I need little time to digest that solution, it looks interesting

 

[Natlek]

Rollers ! I was too focused on that technical solution with balls
Rollers are prefect for this ...............All same , just rollers instead of balls .

 

[JoeBusic]

Just saw this. It's a great idea. Got it from the first scribble. Essentially mimicking a keylock with pins. Only tinkering would be how to achieve flawless ball drop when released. Either with a spring or geometrical form in the blade to force them down when unlocked and turned. Three point contact for strength while the stop pin is a safety just in case. Another issue would be securing the button not to engage when working. A small lever would do just fine. When I get some free time I'll CAD it to see possibilities, curiosity sake.