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What is the purpose of a lockbar cutout and why are they so thin?

Fred Sanford

Fred Sanford

Gold Member
Joined
Sep 3, 2006
Messages
3,135
I'm speaking of mainly frame locks, but I also mean certain liner locks (like the Gayle Bradley). I think that the cutouts must be there to make it less difficult to unlock the knife with your thumb but I am not sure.

What I really don't understand is why so much material is removed that they are often as thin as a cheap liner lock? Wouldn't the purpose of a frame lock be to get a stronger lock? If they cutout is just as thin as a liner lock then why bother?

I've seen many frame locks recently that look to me like the cutout has been left too thin but then again I don't know about the strength of a piece of steel, or tensile strength etc.
 
Some are cut too thin.
It is so the lock can be unlocked, but some manufacturers go WAY too thin.
 
The purpose, as already stated, is to allow the knife to be unlocked. Could you imagine trying to unlock a knife with a 1/4" thick piece of Ti as the lockbar. It would not bend back once the knife is unlocked. (I know 1/4" is an exaggeration but you get my point)

I do agree that some are too thin. I would think since Ti is stronger than steel BY WEIGHT, but not by thickness, that they could make the Ti framelocks a little thicker to instill confidence in the lockup. But I'm no knife designer and a little added thickness could seriously increase the resistance of the lockbar and make it uncomfortable to use.
 
BladeCommander said:
The purpose, as already stated, is to allow the knife to be unlocked. Could you imagine trying to unlock a knife with a 1/4" thick piece of Ti as the lockbar. It would not bend back once the knife is unlocked. (I know 1/4" is an exaggeration but you get my point)

I do agree that some are too thin. I would think since Ti is stronger than steel BY WEIGHT, but not by thickness, that they could make the Ti framelocks a little thicker to instill confidence in the lockup. But I'm no knife designer and a little added thickness could seriously increase the resistance of the lockbar and make it uncomfortable to use.
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Wouldn't it just be easier to use 1/8" Ti and not mill a cutout (or just do a small dip)? It should be able to operated easily, and still be stronger than much thicker steel.
 
Can anyone think of a production knife of current or past that they think the cutout was left "too thin"? Honestly to me, most look too thin. I don't own a frame lock so I have nothing to go by. Anyone have any pics of what would be "OK" vs. "too thin"?
 
David Lowry said:
Can anyone think of a production knife of current or past that they think the cutout was left "too thin"? Honestly to me, most look too thin. I don't own a frame lock so I have nothing to go by. Anyone have any pics of what would be "OK" vs. "too thin"?
Click to expand...
That is a subjective question. Folks that know will likely agree that if no major failures have happened or been reported, it's thick enough wherever it currently stands on whatever model you are referring to. Those that don't know, but think they do will name off a ton and a half of various manufacturers. So in short, my answer is, anything that seems popular and have no reported failures is going to be alright.
 
I just got my first 2 frame locks, a Kershaw Volt II ss and a black leek. I thought the same thing when I first looked, but honestly, they seem to be rock solid. I doubt that it will fail with normal reasonable use.
 
David Lowry said:
Can anyone think of a production knife of current or past that they think the cutout was left "too thin"? Honestly to me, most look too thin. I don't own a frame lock so I have nothing to go by. Anyone have any pics of what would be "OK" vs. "too thin"?
Click to expand...

I'm looking at my brand spanking new Strider SMF and the lockbar cutout looks VERY thin. Still, I'm not particularly concerned about that as it is more than thick enough to hold the lockbar in place so that it can keep the blade from folding. Steel and titanium are surprisingly strong. And stiff.
 
The thickest framelock cutout I've ever experience is my Pohan Leu Bluephin.
I've never had any reason to doubt the strength of any framelock I've owned even though the thickness may seem "too thin".

XM-18 on the left, Bluephin on the right.
XM-18 cutout is 1.21mm, Bluephin cutout is 1.61mm
4k5v.jpg
 
Ramiel, thanks for the pic. See to me the liner on the XM-18 seems too thin. That is a lot of area cut out.....and for what? Is the other knife (Bluephin) you have difficult to unlock. I wouldn't think it would be that hard.


I guess I just feel like lately the cutout has been having too much material taken away simply for ease of unlocking. I say make it a little harder to unlock and keep it safer. After posting this thread I found a few YouTube vids just by searching for "Frame lock fail" and it seems to me that they failed due to the thinness of the lockbar in that cutout area. I also find this subject interesting because it seems almost comical to market a knife as "hard use" with such thinned out lockbars. Something isn't right.
 
David Lowry said:
Ramiel, thanks for the pic. See to me the liner on the XM-18 seems too thin. That is a lot of area cut out.....and for what? Is the other knife (Bluephin) you have difficult to unlock. I wouldn't think it would be that hard.


I guess I just feel like lately the cutout has been having too much material taken away simply for ease of unlocking. I say make it a little harder to unlock and keep it safer. After posting this thread I found a few YouTube vids just by searching for "Frame lock fail" and it seems to me that they failed due to the thinness of the lockbar in that cutout area. I also find this subject interesting because it seems almost comical to market a knife as "hard use" with such thinned out lockbars. Something isn't right.
Click to expand...

I agree on the hard use part, for sure. Do you know if the zt 0200 lock bar has any cut out?
 
tokerblue said:
STR had a really good write up on this.
http://strsbackyardknifeworks.blogspot.com/2012_06_01_archive.html
Click to expand...

Thanks so much for this.

I respect Steve a lot and this was a great read. Really opened my mind as I had no idea of all the variables. I see now that a thicker lockbar translates into other issues too....some good...some not so much. Same goes for keeping it thin too. Just different ways of doing it because you cannot please everyone. I don't envy frame lock makers/manufacturers.
 
I'd give more merit to this argument if there were a bunch of threads floating around describing Ti lockbar failures with snapping at the cutout, but...I don't see any. Is it an 'issue' we're trying to fabricate?
 
fetzer85 said:
I'd give more merit to this argument if there were a bunch of threads floating around describing Ti lockbar failures with snapping at the cutout, but...I don't see any. Is it an 'issue' we're trying to fabricate?
Click to expand...

Probably. Still, if I'm dropping 150+(+) on a knife designed for hard use I want it designed for hard use.

On something like a spyderco Chokwe or sage the cut out seems more than adequate because the knife is not designed for hard use.
 
fetzer85 said:
I'd give more merit to this argument if there were a bunch of threads floating around describing Ti lockbar failures with snapping at the cutout, but...I don't see any. Is it an 'issue' we're trying to fabricate?
Click to expand...

No. Search YouTube for "Frame lock fail" or "Liner lock fail" and you'll see a ton of examples. What I see as a problem more than a blatant failure is the lockbar being too thin to keep itself behind the lock face. When you put a bit if pressure (not whacking) on the spine of the blade and the lock slides off and lets the blade close that has to be the lack of "spring" being able to keep the lockbar behind the blade tang.

Both STR and Cliff Stamp know a great deal about liner and frame locks. Anyone who hasn't read the link above provided by tokerblue should. It says a lot. Also if you haven't seen any of Cliff's videos on YouTube you should watch a few on frame or liner locks. I only found out about these last night while searching for frame lock failures. I have the utmost respect for Steve Rice (STR) and believe what he says due to his experience, same with Cliff.
 
David Lowry said:
No. Search YouTube for "Frame lock fail" or "Liner lock fail" and you'll see a ton of examples. What I see as a problem more than a blatant failure is the lockbar being too thin to keep itself behind the lock face. When you put a bit if pressure (not whacking) on the spine of the blade and the lock slides off and lets the blade close that has to be the lack of "spring" being able to keep the lockbar behind the blade tang.

Both STR and Cliff Stamp know a great deal about liner and frame locks. Anyone who hasn't read the link above provided by tokerblue should. It says a lot. Also if you haven't seen any of Cliff's videos on YouTube you should watch a few on frame or liner locks. I only found out about these last night while searching for frame lock failures. I have the utmost respect for Steve Rice (STR) and believe what he says due to his experience, same with Cliff.
Click to expand...

I didn't search for videos. That said, I don't see any scenario where I would be using a frame lock folder and not be supplying sufficient pressure to the lock bar to keep it from sliding off the tang of the blade. I can see that scenario with a liner lock, but not a frame lock. Hell I can barely disengage the lock bar on my 566 if my fingers are putting pressure on it.

Seems these days people will fabricate tests just to make something fail that don't at all depict realistic or practical use. Whatever. I've had two frame locks. My 566 which hasn't seen much "hard use" and a $30 Kershaw cryo that was put through a lot of "hard use" as my work knife in the HVAC trade. No lock failures to date.
 
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