A new liner lock... The Turbo Lock!

Oct 2, 1998
This is a notice of intent to manufacture...

Of late, liner locks have taken a good bit of heat. They tend to fail under certain uses and I think I may have a solution.

Problem # 1
Liners fail under use because your finger disengages the lock and releases it while in use. This is more a design flaw than the lock actually failing. The locking mechanism is too close to the outside frame of the knife and therefor is inherently dangerous.


Make the lock recessed inside the frame of the knife. Most liners are pancaked between the two halves of the knifes frame. This not only makes the liner too close to the outside but in most cases is not visually or aesthetically appealing.

But how can you push the liner down to release the blade?

This image shows the lock disengaged.


This image shows the lock engaged.

Put a tit on the liner like the one shown in the image above. You simply push on the tit and it releases the blade from the lock and it further allows you to push the liner into the recessed area of the frame.

Problem # 2
Liners disengage under pressure.
Part of the reason is that the liner is engaging the back of the blade and not the blade itself. If you bend the liner and make it fit into a recessed area of the blade it will hold stedfast. The groove cut out of the blade will be the same angle and shape of the bent liner. Therefor pressure on this part would not release the blade and it would not "slip" out of the socket.

But Mike, a bend in the liner would make that part weak and it would bend even further under pressure.
Yes it will bend under pressure but the lock would not fail. The bend would push against the inside frame of the knife but it would still keep the blade from closing.

How much pressure would it take?

That is the better question and that would depend on the material used to make the liner. Titanium would be a great choice as it can be bent to a specific angle and retain it's inherent high strength.

The cool thing is the lock would actually engage the blade.

Imagine trying to keep a door open by putting a wedge between the door and the frame. That is basically what a liner lock does. The door (Blade) gives you a lot of leverage with the wedge so far back. Now take the wedge and have it placed under the door about 20% of the way up and you have a much better way of keeping the door open.

Why make a new style liner lock?
Simple, the fact is they are easy to produce, easy to demonstrate and very easy for the end user to learn. Plus the fact that the industry and the public already accepts liner locks, there would be no real education process like other locks which are on the market and those which are coming to market.

So whadayathink?

Best Regards,
Mike Turber
BladeForums Site Owner and Administrator
Do it! Do it right! Do it right NOW!

Mike -

I'm not an engineer, or even particularly experienced around a machine shop, but I can't see any immediate problems.

I think the thing to do is to produce some "proof of concept" knives. Farm the task out to a few of the talented makers who frequent BF, let each one build a model, and get their feedback.

Good Luck!

A mind all logic is like a knife all blade. It makes bleed the hand that uses it.
-Rabindranath Tagore

I plan to make some prototypes to test the theory. Should it work I will license the idea out to select makers at a very reasonable cost.

The only person I really need to satisfy is Joe Talmadge

If I get his vote "I am da man!"

Best Regards,
Mike Turber
BladeForums Site Owner and Administrator
Do it! Do it right! Do it right NOW!

I think it would be difficult to manufacture this concept on a consistant basis. The cutout would have to match the liner very closely or there would be too much blade wobble. How would you adjust for wear or knife to knife differences? A cam shaped stop pin or a larger stop pin would not seem to work. How big a cut out would the handle require to allow the bend to move over enough to allow the blade slide past? It seems it would have to be a little bigger than the bent portion. How thick would this make the handle? The bent portion could not be very wide and still fit inside the knife. This would make it more suceptible to bending or shearing. It also seems to be prone to problems created by debris (dirt, hair, etc.)jamming the lock.

I do think it is a novel notion though, one I had not thought of. It might be something a custom maker would want to add to his repertoire.

I would recommend that you make an evaluation knife with a blunt tipped training blade to use for testing the lock. I could evaluate it against my heavy bag. I had a liner lock trainer which began to disengage after heavy use.


a knife with a "tit".

I think my wife would get suspicious at me playing with the knife all the time.
Where is the pivot. I assume its after the lock like a conventional liner lock. Then the rear of the blade probably rotates outside of the handle. It could hit, but not cut your hand. Also how is wear compensated?

The problem with the linerlock is twofold. 1, you can accidently unlock with the wrong grip. 2, the slope in the lock is overcome by pressure on the blade, causing to to slip. Your design could be better on both those accounts. However, the same angle that allows the conventional linerlock to slip, takes up the play as it wears.
The groove would be deep enough to take up the slack when it wears like a normal liner lock. However it would never slap over to the other side like some do now.

Best Regards,
Mike Turber
BladeForums Site Owner and Administrator
Do it! Do it right! Do it right NOW!

If I'm understanding correctly, you would need a big hole in one side's scale to allow access to the "tit." You call linerlocks visually unappealing? There are already a few cheaply produced knives that have liners engaged through a hole in one scale, and I think there is a reason these haven't caught on.

Also, I'm concerned by the leverage taht would be applied to this lock. Consider the linerlock as a triangular system where movement at one point (the pivot) is opposed by two points set as far as possible to the sides of this movement (the stop-pin and the locking liner). In your system, the liner would be inline with pivot, so it would be resisting force that would tend to bend it in one direction or the other. This is hard to express in words, but if you imagine the circle described by the blade's motion, linerlocks create a line tangential to this circle and your system would be more perpendicular to it - result, a force that would push your liner side-to-side instead of nearly straight back.

Your contact points would seem to be the *sides* of the part that inserts into the blade, not the front as in a linerlock. Also, a linerlock requires tight tolerances but at least the tang contact is easily accessibly to adjust by grinding - the "slot" required by your system seems like a production nightmare.

I'm not trying to rain on the parade. Much of my criticism probably stems from not understanding a complex 3D system from a 2D image. Maybe more pictures? (You could start by fixing it to "handle" - "Handel" is a composer). Make prototypes, see how they work. You don't need a whole knife to see this system in action, and that'll get you lots of answers (and questions) to work from.


(Why else would a bear want a pocket?)
The problem I see is the way load will be applied to the lock. No liner that I know of has a square cross section, they are all rectangular in shape with one of the dimensions being much longer than the other. This means that the liners are going to have different strengthes in different directions. For example hold a yard stick with one hand at each end and the wide sides on the top and the bottom. Now try to bend it into the shape of a smile - easy. In this case you are trying to bend it with respect to the weak axis of the cross section. If you hold the yard stick in the same manner but this time with the thin side on the top and the bottom you should find that it is much more difficult to bend the yard stick into a smile shape. This is because you are trying to bend it with respect to the strong axis. A liner lock is designed so that load is applied to the strong axis of the liner. Now as a last test hold the yard stick again at both ends but this time try twisting it. Once again this is pretty easy. I think the way load would be applied to the "Turbo Lock" would be similar to torqueing the yard stick. This means you are going to need a more square cross section for the lock. Which would mean that the knife handle is going to have to be very wide and that the lock may be quite stiff. Not to mention it does not appear in the diagram that there is much metal-to-metal contact between the blade and the lock in the direction load will be applied. I don't think it's necessarily a bad idea but it may be tough to implement effectively.

Just my thoughts,