Problem with liner lock slippage

Steel Sprocket

Steel Sprocket

Joined
Mar 6, 2012
Messages
21
I am asking for help with a liner lock that seems to have a mind of its' own. I have a custom tactical from a well respected maker who I won't name. He wouldn't be served by this post as I don't believe that it's his design problem. What's happening is that the blade wants to close on its' own when pressure is applied to the spine. The spring liner that's supposed to keep the blade open bows slightly under pressure on the blade cam and simply slides back toward the frame which allows the blade to close. As this is a dangerous condition I have not used this particular knife for a long time.

Question no.1 Is this a common condition with liner lock knives?
Question no.2 What can I do about it?

If there is something I can do about this or if anyone can answer this riddle please let me know.
Thanks!
 
I'd be willing to bet, a truly 'well respected maker' would be willing, maybe even anxious, to fix that for you. Whether it's an issue of his design or not, most custom makers don't like the thought of problems like this getting away from them. Especially if it's a safety issue. Among custom makers, reputation is everything, and the respect they earn is built on quality. Most would bend over backwards to make sure you get the quality that was intended from the start.

The very first thing I'd do, is get in touch with the maker and describe what you're seeing. So long as you keep it matter-of-fact and not in an accusing tone, I'd bet he'd want to resolve it for you, one way or another.
 
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Thanks David,

I was reluctant to mention this but I met the maker at the Solvang Knife Show about 4 years ago after reading advance notices about who would be attending. I brought the knife with me and mentioned this issue whereupon he graciously agreed to take it back to his shop in Kentucky. He actually performed a nice job re-profiling the tanto's kissaki and the issue with the unwanted blade closing went away for a brief time but that didn't last long. As you said he was more than casually interested in fixing the problem but it persisted.
I suspect the cam/liner point of contact may be too smooth and being a function of friction the knife has to be taken apart and major parts replaced.
I was interested if anybody else has heard of this type of failure. I have a very nice frame lock Sebenza that I bought from Chris Reeve at the same show. The frame lock has a very positive lockup and I suspect that liner locks have a fault in that their thin metal liner tends to slip inadvertently. I dunno.....
Larry
 
I'd suggest contacting the maker again. He'll fix it again and in the process will gain more in depth understanding on the mechanism behind liner lock.

One question: do you lube the knife? If it gets between the mating surface, the friction that should hold the lock might have been reduced.

Liner, frame and axis are three that need friction to stay in place against impact force landed upon the spine that could jar them from the seated position. Static pressure should not result in such slippage on a properly designed one.

It is also possible that the tang ramp angle is beyond the norm, so static spine pressure is transferred to become lateral force pushing the lockbar out. If this is the case, it's a design issue.

Check out STR's sticky on tips & tricks where he describes his findings.

Lastly, a close up picture of the tang ramp & lockbar can be useful & nice knife avatar. ;)
 
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To answer your question:
1. It is common in poorly executed liner lock
2. If above is true, nothing much you can do short of re-machine the tang & lockbar.

However, sometimes it can be fixed by increasing the lockbar spring tension towards the tang.

These fixes are best done by the maker, especially on a custom. We're not talking 10$ Sanrenmu here :D that I won't hesitate taking it apart and doing it myself, with the risk of ruining it ...
 
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David and Chris,

Thanks for the input. The liner bar actually bends before slipping whareas a frame lock is too stiff to bend. I bet that lube may be part of the problem so I'll de-grease the bar and see if that helps. After that a call to the maker is in order.

Good deal!

Larry
 
Chris "Anagarika";10646483 said:
To answer your question:
1. It is common in poorly executed liner lock
2. If above is true, nothing much you can do short of re-machine the tang & lockbar.

However, sometimes it can be fixed by increasing the lockbar spring tension towards the tang.

These fixes are best done by the maker, especially on a custom. We're not talking 10$ Sanrenmu here :D that I won't hesitate taking it apart and doing it myself, with the risk of ruining it ...
Click to expand...

True words! Usually well known maker offer a lifetime service on their products.
As already said you could carefully add some tension to the liner but avoid any polishing/grinding of the liner/tang especially freehands, you will surely destroy the coupling.
One question: have you tried before by yourself the "table test" hitting hard surface with the spine in order to see if the lock is ok?
Here in europe is common but in my poor opinion is very hazardous because you usually destroy the coupling liner-tang.
bye bye
 
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