Bull Pivot Barrels, Bull Stops, Super Duty Hardware and Thin Lock Cuts

Shown top is a production Emerson HD7 mangled at the point most all frame locks fail when stressed, showing what happens when one gets stressed to the point that something has to give. There is a large variance from company to company and from knife to knife in location of the lock cuts and how they are done but one thing they all have in common is that they are taken down pretty thin at the lock relief where we makers bend the lock to put spring in it.

Here we have two Emerson HD7 models done in different years. Note the different lock cuts both in the way it was done and for the location.  These variances occur in many models across the board and from makers.

During testing I've done, some very thin cut frame locks collapsed like that top picture or worse at 65 to 68 pounds of free weight hanging on the end of the knife. None tested made it to 100 pounds. Some liner locks actually hold more  weight than frame locks done like those in that picture. A strong liner lock will hold 100 pounds. A strong liner lock like one in stainless steel .080 thick may hold 130 pounds but even that depends on if it has thin lock cuts, no lock cuts  and many other factors. 


Contrary to how many readers may feel about that picture above. That my friends is a design that deserves praise for defeating the way it was engineered to go. That HD7 above did its job and so did the designer/maker of the knife. I doubt any sutures or ER trips costing great amounts of money were needed with that defeat. We should all pray to be so lucky should we be the on the unfortunate end of a defeat ourselves one day.

How and when a lock fails just depends on so much including the length of the knife tested and the blade length, lock thickness, lock material the lock contact and more. As you may have figured out that 100 pounds ain't much weight compared to many of the locks we all see these days being tested on youtube using different lock types. Triad locks by Cold Steel for example will hold two to five times that weight listed above in the same tests and fair better in about all other tests as well from spine whacks to overstrikes and more.

Still though there are other advantages to frame locks in that the hand helps the lock to absorb some of that shock it may see in use that cannot be duplicated to appreciate when doing static load (free weight hang) tests and in the hand the frame lock can and does do an aweful lot of hard use jobs. Even a frame lock with the contact worn such that there is clicking from the up and down blade play from the wear does not prevent the knife from being used and even used hard. Its still my personal favorite type of lock because it need not hold a house on the end of the knife to be useful guys. For one frame locks are usually thinner in the pocket carrying easier even when extra long and they are open designs and as a result they fair better in muck than other designs!

Don't let it sway you from a liner or frame lock just because this can occur. Its still a very good design for most all things we do with our knives. Do we have to take the lock cuts that far down in the frame locks? No we don't. I personally wish makers or manufacturers offered some kind of tough use option or "He Man" option of their own to allow one to get a knife a bit stiffer and thicker. Its too much to ask though. I've sold some done that way that folks have returned for me to thin more with more profound lock cuts so they were not so hard on thumbs. Its not for everyone to leave the lock cut thicker. With lock cuts left thicker comes a host of other things.

Done with cuts left thicker it will not be a flipper blade unless you licensed IKBS. The detent ball really works and holds the blade closed well when the lock is stout because when the lock is stout the spring tension is too and sometimes the spring tension is such that you can really feel and hear the ball on the blade and other times the lock is so stout that if you are the type that likes to flick your knife open and closed a lot its just going to cause pre-mature carpel tunnel and a really sore thumb or a really big callus if you keep it up. You'll also notice flattened detent balls on the lock a lot quicker when the lock is done this way.

Makers and manufacturers have to please a lot of folks. Its better if the action is easy and smooth and thats what everyone wants or they'd complain about it. So these makers doing a lot of these and manufacturers trying to appeal to a large audience do what they feel is needed to make it strong enough to serve the owner, yet weak enough to be easy to use easily and with comfort once the knife is broken in properly. It doesn't happen often but it happens and try as one may to warn of it some react with anger at times when these things are pointed out. Its not often easy to look at your own favorites with the same eyes you use to view the not so favored. 

I've said before that if people would just for a moment take off the blinders spending half the effort examining the knives they love with the same eyes they use to pick apart knives they hate maybe then they will see more objectively for what is right in front of them instead of being blinded by bias, but unfortunately that is often times like asking someone of one religious faith to examine their own the same way they examine and pick apart opposing faiths. It just isn't happening. With some the bias is so strong that no matter what you tell them they don't want to hear even what amounts to common sense regarding their favorite lock type. 

Like any chain there is a weakest link and any chain is only as strong as its weakest link. In liner and frame locks that weak link is the lock. It doesn't matter how much you beef up the other parts of the system because they have no effect other than making that system more out of balance if the lock remains the same. You can stick a bull pivot 1/4" in diameter in there and you can put a bull stop pin 3/16" in diameter or larger and coat it with G10 scales and a super duty set of screws in it. But if the lock is still a gents liner lock in .045 thickness under all that coating its not advanced one bit more really because those locks are still the point where the knife will fail in say a free weight hang test.  Whats more it would probably fail at the same point it would fail if the knife had bone handles and bolsters and a 1/8" stop pin diameter with a 5/32" pivot barrel using that same lock! 

The truth is even a 5/32" pivot and 1/8" stop pin would still be stronger and outlast most locks in a free weight hang test of this lock type. Some companies have put bull pivots and bull stop pins in their knives ever since they realized they sell better in what I call 'wolf' clothing and while we can't ding them for some marketing to sell their wares we can see through it if we take time to look deep enough.

I attributed it the other day privately to a guy like this. Looking at it from the stand point of an automobile lets consider and say for arguments sake that a gentleman's liner lock is like a four door Ford LTD family sedan. (I'm sure some old farts out there still know what an LTD was) Now you can do a lot with that car as it has a big foot print, a big trunk, a powerful motor, a wide track and comfort for the driver and while you may be able to toughen it up by sticking balloon tires on it, and a cattle guard bumper on the front and even by painting it camo in a hard coat shell with a couple tactical spot lights on the side for hunting and a deer rack on the roof with a winch up on the front bumper but its still a Ford 4 door family sedan underneath and it always will be.

Thats the myth of bull pivots, bull stops, G10 scales, tactical looks and grips, and whimpy thin long locks that were never designed for what they are used for in a nut shell description. If its still a gents folder starting out on the frame, all that nice hardware hasn't really changed it. If the four door sedan has all that great stuff you may get a little further up the goat trail in it thanks to those bigger tires but it will never be the four wheeler you really wanted. Like I said, sometimes the truth sucks. I think people feel this intuitively when they would mail me work to convert from thin flexible to beefy stout. In some of the cases where the locks replaced were .050 or less in thickness the trade off even with a huge lock cut still favors the rebuild with the only drawback being the cost to do the job. 

For what its worth even though a frame or liner lock can fold, kink, or bend and deform similar to the picture shown here these are not the most catastrophic defeats of a lock that one can experience and one could argue that makers create the circumstances such that if and when the frame lock or thicker liner lock type knife gets stressed to that point of something having to give then they'd rather it be programmed in so to speak so this is what occurs just as shown in the picture above of the mangled lock. Of course this relies on the makers skill at creating a perfect contact that allows this to happen instead of the much worse opposite where the blade is free. My contention is that in the hand the frame lock is very unlikely to defeat once gripped properly. 

If you are going to have a defeat I guess what I'm saying is that this would be the way to do it as opposed to the way that requires sutures and costly tetanus shots and more. Most of the time the blade is still opened and locked in this type of defeat albeit permanently with defeats of this type on some until you disassemble the knife but so long as fingers are not cut bad and maybe a bad pinch and a bruised ego are the worst of your problems followed by some choice words usually reserved for sailors its a not as bad a lock defeat as other types of defeats can be.  

As you can see from most of my old frame lock conversions I used to do a lot of my lock cuts to spring the lock just a bit different than most you'll see from other makers. For one mine are left thicker at the lock cut usually and as a result of a customer requests for me to do that. In fact it was people that bought frame locks from other makers/manufacturers and liked them but wanted more that led me to looking more into the lock cut. My first question to myself was why not do one without a lock cut so thin? Lets see what happens. At other times I was contacted by customers who wanted a folder converted from a thin liner lock that they could feel flexing in use. This turns a lot of people off to have a tactical folder they can see the lock flexing on and so the request was to convert these to a beefy frame lock. I simply filled customer solicited requests to get me into this. I've always felt the frame lock sides I did were stronger simply because you could feel the difference in spring resistance quite a bit and they certainly required more ummmph to release the blade. Then there is the visual thing. They do look the part of beefy and to some just the look of beefy is more important than whether it actually is which again plays into that bull pivot appeal! Boy they wore on the thumb and flattened a detent ball good and quick though! So, I'd probably put a shallow lock cut not so drastically thin in a frame lock made for my own self. Some have asked me what is the best thickness for a lock cut in a frame lock folder or thicker liner lock folding knife. The truth is you could ask a thousand makers and get a thousand different answers I think. I like about .059-.060 personally. You can certainly get by with thicker though. 


My point is and always has been that the point of catastrophic defeat could be stretched out a little bit more than 68 pounds just by simply leaving the lock cuts a bit thick on the frame locks for customers wanting it to make them feel better about their folder but I think most makers figure that even if left the strongest it could be the lock is still the point of defeat and it may hold 130 pounds max if you are lucky unless you use the thickest materials you can use and even then the lock cuts negate a lot of that strength! With some tweaks and planning the overall strength of the folder could be more balanced by strengthening the lock some to try to get it closer to what the other parts of the system are already at but no matter what you do the lock will never catch the other parts of the system for strength. You have to go to a different type of lock to get that. . Make no mistake no matter how much you love the lock. When talking about liner or frame locks, the lock is still the likely weak link in the chain regarding the system, A/K/A other parts of the folder. I like to think I've just improved that weak link a little bit more to bump it up to a bit more capability by leaving my lock cuts thick rather than thinning them down so radically just to make them amazingly easy to move but also just as easy to hyper extend the lock out the wrong way if one were to take the pocket clip off or pull their clip to make it stand up from the folder higher so it doesn't grab pockets so tight. Most clips act as a block for lock travel and while they don't always work that well if you notice you'll see that many makers incorporate this double duty aspect of the pocket clip with their frame locks. 

Just because I did some of my frame locks with thicker lock cuts does not mean the same thing would not or could not happen with one of my folders as what you see in the picture here above. In fact it is likely it still would happen to one of mine and very similar to what you see in that picture above should mine be pushed to the same limits only by the time that happened to mine you would really have to stress the knife to double or more the force that it took to even begin to duplicate a situation like shown here. That isn't bragging. From my stand point it is simple physics. Oh I realize my folders may not open quite as silky smooth with my lock cuts left as thick as some of them are but if thats what folks wanted they'd buy the knives someplace else instead of seeking me out.

For at least the few folks that have used me when I offered these conversions they wanted beefy and strong and were not too worried about a knife they sat around flicking opened and closed all day long like a replacement habit for nail biting. They pull the knife out when needed, it does the job, they put it back and they feel a little better about knowing that if they really lean into it that it should take a bit more before the lock ever reaches this point but its not changing the fact that the lock will still be the first thing to go for a controlled burn so to speak.

If anything, the way I do mine with an 'air bag' built in for a safer defeat of the lock is still engineered into the design so that should the system get stressed to that point of something having to give that it would still go just as the picture above using one of my knives too. This is what shows quite vividly in my testing even though it takes a bit more stress and strain to get mine to that point compared to most others I have bought built like above, and that is due to how I build them regarding the thickness and the flatter lock contact I use for the lock itself which makes it more stable on the blade. The funny thing is I use a 3/16" pivot, and a 1/8" stop yet my knives test out stronger than all I've tested with bull hardware and thinner locks once again proving that the weak link is the culprit no matter how much you advance the other parts of the whole.

Lastly, its not really a weak design even made as shown above with all that titanium taken out of the thickness in the back of the folder. Can it be better? Certainly it can be more balanced in the system that makes up the folder parts yes but so long as you still design the knife and engineer it such that the lock would go first and hopefully just as shown above when it does reach that point of something has to give when the system gets stressed, I think the frame lock design is the most solid of those being used today. Which once again illustrates why I like the frame lock so much for all it brings to the table. You don't hear about defeats of this nature often enough to the thin lock cuts to be a problem so therefore I'd say its really not a problem to concern yourself with. If however you feel you want one that just looks beefy discuss it with the maker and maybe they will compromise with you to give you some visual appeal with the lock cut done slightly differently on your folder. Never hurts to ask. 

While I'm a big big fan of the Triad lock and all it brings, and I can say I own enough of them now I want to stress that frame locks are still one of my favorites among locks in folding knives. Even though it is most often not even as strong as some liner locks I find they are strong enough and to me they are much more reliable giving a sense of security once your hand is wrapped around it good. Of course some models prevent this hand wrapping of the lock by the position of the pocket clip so not all instill this confidence for me personally. I found some like the JYDII to be particularly appealing in frame lock due to the flipper being out there when its opened. It is hard to imagine the blade coming back to bite you on one of these flipper models even in one of the liner lock models. In this case since you'd get a bad pinch at worse case scenario I'd have a good feeling carrying one of these even if a liner lock. I like knives with the choil built in because when you have a choil and the ability to position your index finger in front of the pivot it is also hard to imagine it defeating if your finger is there blocking travel. In a way in these grips the knives become a part of the hand allowing greater versatility with that sense of security so I personally find this so appealing that knives offering either flippers or choils in frame locks of this type are my main knives to carry most of the time as my primary EDC. I have the one Triad locking model in my rotation in the way of that Mini AK47 which I do tend to favor. Its always partnered with something though as the mini AK is my left side carry piece coming out in reverse grip most always for fun with that thumb plate on it. I love that thing! Anyway, the other pocket always changes and it may have any number of frame locks from day to day or other liner lock type folders with built in choils or flippers. I like those and favor them again due to that feeling they are just inherently more reliable by design. I mean can you imagine the ZT0551 even closing on you in use? It would be a bad pinch at best. Can't argue with that in my opinion. 


 The way I have seen some lock backs break when stressed it seems obvious this type of lock would be a more disastrous defeat. Based on how a lot of people use their Cold Steel folders it seems to me that when a Triad does fail that it is likely to have a great deal of force and pressure applied to it to make that happen. This could be quite disastrous in the hand and it would be more likely to really mess up the user as well as itself when it happens. So in my final analysis as much as I love the Triad lock, the frame lock design may in fact be the overall higher rated lock for effective and safe use compared to all others because its more in balance with the abilities and strengths of the human using it.. 

STR