Framelocks...An Observation

B

BARRY JONES

Joined
Oct 2, 1999
Messages
834
This may be a little off topic but I need to get this off my chest.

I am currently working on my first framelock folder. 2 actually. I am making them a little
different than most other makers. I am not putting that little relief at the rear of the
slot that is cut to make the lock. Here is why:

Nearly every person I know that owns a framelock (most makers too) say that the
framelock is much stronger than a liner lock. Yet they mill or grind a relief at the rear of the lock. They put that relief there so that the frame will be easier to bend. Easier to close too. All of the framelocks I have seen have this relief milled to about the same thickness as liner stock would be.Heck, I have even seen framelocks where the relief is milled to less than .040 on a .125 thick frame. The bend that is put into the lockbar to make it engage the lock notch usually starts at the relief.

Doesn't anyone realize that the relief weakens the lock and makes it little better than a liner lock? IMHO, the strength of the lock lies in the strength(springiness) of the spring and not in the thickness of the material used to make the lock bar.

I am not dissing any makers work here. I am also not against linerlocks or framelocks. In
fact, I think the linerlock is an excellent lock mechanism if made properly. The framelock is even better but once again, if made properly.

I want to know what you makers and users think of this.

BTW, I understand that you have to put a relief in some framelocks because of the
thickness of the material used. Otherwise you would never be able to unlock them.

------------------
Barry
Jones Knives
"NEW Knives"
http://albums.photopoint.com/j/AlbumIndex?u=126319&a=5922856
"For DUTY and HUMANITY!"
Curly, Moe, & Larry
 
FWIW, and keeping in mind that my technical qualifications are "none," I've wondered whether the relief might be a weak point in the design of frame locks. Glad to hear that you're going to be building one without it. Can't wait to see the pictures.

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Dave

Let no one ever from henceforth say one word in any way countenancing war. It is dangerous even to speak of how here and there the individual may gain some hardship of soul by it. For war is hell, and those who institute it are criminals. Siegfried Loraine Sassoon
 
veeeerrrrrrry interestink! You know that Chris Reeves is a TRAINED tool and die maker right!? He sorta came up with this....so there has to be a GOOD reason.....If you just bend .125" ti you STREEEEECH the outside of the material quite a bit....it can actually crack and eventually break (believe me I KNOW!).....You can certainly leave it thicker......but I believe it is essential to cut at least half of the material off of a .125" thick framelock.
smile.gif

postscript: With a .050" web at the back of the lock you can still bend the lock to be as strong or as light as you wish....one of the real strengths is the RIGIDITY of the lock and the large chunk of titanium available for an interface! there is also the plus in that while you are holding the handle you press IN on the frame lock whereas a liner is inside the handle.

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http://www.mayoknives.com
John 1:14
Love is Stronger than Death!

[This message has been edited by tom mayo (edited 03-18-2001).]
 
The strength of the frame lock lies not just in the size of the stock. Very few liner lock failures are of the sort where the liner physically fails, so I don't see why you are concerned that the frame milled to the same size is at risk of failing. Liners tend to come off the face of the tang through grip forces, impact and wear. The frame lock is reinforced by the grip in these instances.

The springiness of the lock is also not only dependent on the thickness of the material. The hardness and elasticity also have their share of the effect. But as you note, the milling allows the whole design to work more elegantly and comfortably. From a strict functionality argument, the force required to operate the lock needs to be within the comfort level and dexterity through one finger of an average, or below average person. Therefore that is about the force or spring strength the lock can exert to keep the knife safely open. As should be apparent by the strength of the frame lock, the required springiness is relatively low compared to the amount of force the lock can withstand through the blade and at the pivot.

As long as the remaining stock is capable of withstanding the designed forces the knife is intended to encounter, or even some level beyond, your argument is meaningless. You would need to show that that size and shape of metal can't do the task it is supposed to, evidence which is even lacking anecdotally.

Further, the small material area is the spring. The large "bar" that extends to the tang interface needs the extra size to ensure rigidity to keep the lock operating as designed. Although integral with the spring and the frame, only that one small area is "sprung". As you noted, the small metal area is flexible compared to the whole, the larger bar isn't, at least under the loads they are designed for.

Think of it this way. Springs flex. If the whole bar was the spring, the whole bar would flex. That would be undesirable and disconcerting to the user to feel the knife flex in the grip under loads.

FWIW, I started writing this before the Tom and Kit responded. They give good insight here and I bow to their answers.

Phil

[This message has been edited by phatch (edited 03-18-2001).]

[This message has been edited by phatch (edited 03-18-2001).]
 
What Tom said.

It's getting even scarier. I keep agreeing with him
smile.gif


I've did them with and without the relief and with it on the inside and the outside. I've found it best to relieve the inside down to about .075.

 
I too believe that the most important advantage an integral lock has over a standard liner lock is reliability. With the user's hand wrapped around the frame leaf, failures from torquing and white-knuckling should be vastly reduced if not eliminated altogether. Which means that one of the critical design features of a frame lock is making sure the clip does not interfere with the user's grip around the frame leaf.

Another feature that's interesting is that where the frame leaf meets the blade tang, it will be much thicker than a liner lock. That means more friction between leaf and blade tang, which in theory I suppose provides a little more safety margin.

It is interested what you say about the notches in the frame lock, but even if true, the strength of a liner lock seems pretty damn good to me already. It's the reliability of the frame lock that I like.

Joe
 
In college physics, friction was taught with surface area not being important in most cases because the net force determined friction. There were special cases where surface area counted. Is steel to Ti such a case because of the galling? Steel to steel wouldn't do that would it?

I don't see how surface area is applying force in this situation, unless it's the special case.

Phil

[This message has been edited by phatch (edited 03-19-2001).]
 
phatch-

You're right- surface area is not related directly to friction- it's the applied force that counts. But Joe is right, too- think of it as a contact patch. The thicker the locking bar, the more movement it's going to take before the inside edge of the bar is no longer engaging the tang. (of course that depends where the bar sits on the tang to begin with) It's good insurance- although the measured friction wouldn't really change be it a thick or thin locking bar.

Firebat- fan of integral locks



------------------
Name's Ash......Housewares.
 
I believe the most important point is that the area milled out or thinned in the frame lock is under direct compression with little or no torque in any other direction. Compression is where most metals are the strongest.

With the liner lock, there is a side torque applied to the entire length of the bar due to the angle of the tang and the fact that it is thinner over its entire length.
 

Several factors come into play on all locking liner type knives. These are just my opinions and factors I have found for my own reference.

1. locking liner type knives are as good as the precision they are made to. The blade engagement angles are very important. Also the liner thickness, the way the liner is bent, and relieved.

2. Frame locks with their thicker side plates are better for lock up . If the Lock bar is straight from the relief in the frame it will naturaly be stronger. A bent lock bar (CURVED) IMHO has already started into the failure mode. It is easier to fudge a bent bar into working than real precision. This is the result of the geometery being wrong in planning. The lock bar should be as straight as possible.


The frame lock has a wider surface engagment area on the back of the blade. Less wear is seen over time. Also the bar itself is thicker. This means that it will not flex as easy as a thinner liner. If the lock bar itself does not flex as easy this means its a better lock if made right. The frame thickness is important also. If the frame is thicker the bar dosent flex as easy when the lock engages . The lock bar has a stronger frame to work with as a atttachment base.

As for the relief thickness on frame locks.
If you relieve the bar thickness to much you are back to a locking liner type knife with a wide face. Its still stronger. The lock bar dosent flex as easy, but your defeating the purpose of the frame lock.

Looking into the design factors below helped me understand the difference between these two types of locking liner knives.

1. There are ways of making a frame lock function with thicker sections in the relief area.

2. The length of any locking liner lock bar is another factor that needs to be addressed.

3. The lock engagement face to the back of the blade is critical on all locking liner type knives . Frame locks and locking liner type locks require different locking angles on the back of the blade.
wink.gif


One more thing is the lock angle in relation to the natural centerline force of the blade.
Most locking liner type knives fail because of a few important factors .
All around precision for the whole knife assembly, (sloppy pivots, blade wobble, side plates shucking),
improper lock design (length, width), angle relation to the back of the blade for the type of lock (frame or liner), and centerline axis - lock angle face- in relation to the whole knife.

One thing to remember . The tighter and more precise the knife is , the better your design parameters for all the lock relation factors have to be to make the lock work right. As always the materials used for the liners or frame play a big part in the whole make up of the knife.

Just my .02 cents worth.

Ill post some pics in a month or two of a lock strength test procedure I have to complete for lock strength proof on a prototype I am working on.
Should be interesting!

------------------
Web Site At www.darrelralph.com
MADD MAXX !
 
Thanks for the pleasant and enlightening discussion. I believe that all you guys have made some good points. Some of which I didn't think of so I stand corrected.

I have completed the mechanical work on my framelock. All I have left is the finishing (rounding of corners and polishing). I bent my "spring" straight as DDR mentioned. The bend was made at the rear of the lockbar (where most put a relief). The knife locks up SOLID. I have no problem unlocking the lock. BTW, I am using .090 Ti for the frame.

I guess it really comes down to common sense when cutting a relief in a framelock. After making my first framelock I have come to the conclusion that I would definitely put a relief in when using material thicker than .090. It would be damn difficult to unlock without the relief.

dsvirsky,
You will get to see the completed project up close if you can make it to the gun show this weekend.

------------------
Barry
Jones Knives
"NEW Knives"
http://albums.photopoint.com/j/AlbumIndex?u=126319&a=5922856
"For DUTY and HUMANITY!"
Curly, Moe, & Larry
 
I agree with the statements made about linerlocks in that if made correctly or properly, they can be as solid as anything else out there that folds. I do have, in my knife case, $200+ liner locks with blade play and lots of drift of the lock bar that are "bulletproof" (or advertised so)and $60.00 liner locks that are tight and give me confidence they won't fail in any reasonable folder use. My Sebenza I have every faith in, but I have an inexpensive liner lock that appears every bit as strong!
Luck? No, good design, good geometry and really good quality control.
Of course, YMMV.

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Buck Collectors Club Member # 572
Dedicated ELU
Knifeknut(just ask my wife)
Sebenzanista
 
Brian
Yes ... any locking liner that is built right will do fine. The question is long hard use.
The type with wobbel ect will fail sooner in most cases from premature parts wear. Lock pressure can sustitute for good design also.

Just things to look for!

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Web Site At www.darrelralph.com
MADD MAXX !
 
Outstanding thread gentlemen!!!!
Barry, I use .090 ti on my liner locks. I don't feel it's too heavy or hard to release the blade and it just makes sense that a thicker locktab will be stronger if the design is right.
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Take care!! Michael
jesus.jpg


Always think of your fellow knife makers as partners in the search for the perfect blade, not as people trying to compete with you and your work!
http://www.nebsnow.com/L6steel
Buzzards gotta eat, same as worms!!!

[This message has been edited by L6STEEL (edited 03-21-2001).]
 
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