Lock geometry question

[arskrg]

Recently dropped over $400 on a folder and the lock stick is driving me crazy.
I've cleaned it, graphited it a few times, cleaned it again, sharpied it a couple times, and it's still sticky.

I did notice that the lockbar isn't flat against the tang, it meets at a V. Meaning only the inside edge of the steel lockbar insert meets the tang.

Is this normal?

If so, I've never noticed it before on other knives. Anyone besides me feel like this could possibly be the cause of the stickiness?

 

[Comeuppance]

Lock stick often occurs due to metal galling. Putting some variety of lubricant on the contact surface could help.

It’s possible that the force and friction being experienced by the relatively small surface area of the lockbar is causing this. Alternatively, if I’m interpreting your description accurately, the lockbar is meeting the tang of the blade at an angle - which could cause the edge of the lockbar to catch or gall onto the minor surface irregularities (machine finish) of the blade’s tang.

This is all wild speculation on my part, to be honest. I think the most constructive thing to do here is contact the manufacturer and see if you can get them to fix it.

 

[marrenmiller]

Liner and frame locks aren't supposed to sit flush against the tang. They're supposed to only touch on a single corner of the lock bar on the inside edge.

Recently dropped over $400 on a folder and the lock stick is driving me crazy.
I've cleaned it, graphited it a few times, cleaned it again, sharpied it a couple times, and it's still sticky.

I did notice that the lockbar isn't flat against the tang, it meets at a V. Meaning only the inside edge of the steel lockbar insert meets the tang.

Is this normal?

If so, I've never noticed it before on other knives. Anyone besides me feel like this could possibly be the cause of the stickiness?

 

[rje58]

If you are saying that the lockbar is pointed - sharply - toward the tang, where they meet, then no that's not normal and yes it's a problem. Or maybe I'm misunderstanding. Photos might help.

Can you return it to the manufacturer? Would you mind telling us who made it? Some brands have known issues with lock stick, and some may even have known fixes.

I did notice that the lockbar isn't flat against the tang, it meets at a V. Meaning only the inside edge of the steel lockbar insert meets the tang.

 

[arskrg]

Liner and frame locks aren't supposed to sit flush against the tang. They're supposed to only touch on a single corner of the lock bar on the inside edge.

That's what's happening. I wasn't aware that this was normal.

 

[Lapedog]

That's what's happening. I wasn't aware that this was normal.

Yes for a proper lock up frame and liner locks are supposed to only contact a portion of the lockbar, usually at the bottom of the tang. This forms the stability of the lock by causing three points of contact, lockbar to tang, the pivot and the stop pin. A lockbar sitting flush against the tang is not how a stable lockup is achieved.

Make sure there is no oil on the lock face of the bar or tang. That causes major lockstick. Graphite and sharpie sometimes help but honestly if you plan on keeping the knife just use it and the lock stick will go away as the lock breaks in. Eventually enough of the lock will be worn that the lockstick should cease.

Also believe it or not when Michael Walker invented the modern liner lock he actually considered lock stick to be a feature, not a fault. He felt it made the lock more secure.

 

[matt009au]

I quite like a bit of lock stick as long as it isn't crazy bad!

Are you still able to unlock the knife easily? If so just use it and the lockstick will go away in time.

 

[BellaBlades]

It's not only the geometry but also the grit at which the lock face is machined or milled.

Too smooth is may slip or too rough it may stick horribly.

 

[Mick_1KRR]

Liner and frame locks aren't supposed to sit flush against the tang. They're supposed to only touch on a single corner of the lock bar on the inside edge.

Yes for a proper lock up frame and liner locks are supposed to only contact a portion of the lockbar, usually at the bottom of the tang. This forms the stability of the lock by causing three points of contact, lockbar to tang, the pivot and the stop pin. A lockbar sitting flush against the tang is not how a stable lockup is achieved.

Make sure there is no oil on the lock face of the bar or tang. That causes major lockstick. Graphite and sharpie sometimes help but honestly if you plan on keeping the knife just use it and the lock stick will go away as the lock breaks in. Eventually enough of the lock will be worn that the lockstick should cease.

Also believe it or not when Michael Walker invented the modern liner lock he actually considered lock stick to be a feature, not a fault. He felt it made the lock more secure.

Let's back this truck up a bit for a second. This is true but I think this point needs clarification. The lock bar isn't supposed to only contact by a tiny tip on the very corner of the locking bar, ever seen what happened to Strider when they used to use this geometry with their radius tang? That's why Chris Reeve knives have later lockup, because more of the lock bar is sitting slightly more flush against the tang adding stability and LESS wear on the lock bar it's self. Striders tiny edge contact point made the lock bars wear out insanely fast, we are talking a few months and they had lock rock. It's simple, the smaller the contact point the high the rate of wear will be, little surface area VS big surface area - big surface always wins. The lock bar doesn't need to be 100% flat against the tang, but a bit more that the tiny edge should be there. That's why you see 15-20yr old Sebenzas that have lock bars settled in almost to were they are dead flush with the tang and almost stop wearing for good. The mating surface is big and stable which reduces the wear rate significantly. Seen it on dozens of my knives after years and years of use. Take a look at the sebenza, much more flush against the tang and it will stay there for almost ever.

Now this Strider has the wrong kind, only the very edge wearing against that big radius tang. The huge radius caused that tiny tip of the lock bar to always be the part touching it, and they worse out quick smart, hence why strider changed their lockup geometry in recent years fixing the issues with wear and lock rock.

 

[Lapedog]

Let's back this truck up a bit for a second. This is true but I think this point needs clarification. The lock bar isn't supposed to only contact by a tiny tip on the very corner of the locking bar, ever seen what happened to Strider when they used to use this geometry with their radius tang? That's why Chris Reeve knives have later lockup, because more of the lock bar is sitting slightly more flush against the tang adding stability and LESS wear on the lock bar it's self. Striders tiny edge contact point made the lock bars wear out insanely fast, we are talking a few months and they had lock rock. It's simple, the smaller the contact point the high the rate of wear will be, little surface area VS big surface area - big surface always wins. The lock bar doesn't need to be 100% flat against the tang, but a bit more that the tiny edge should be there. That's why you see 15-20yr old Sebenzas that have lock bars settled in almost to were they are dead flush with the tang and almost stop wearing for good. The mating surface is big and stable which reduces the wear rate significantly. Seen it on dozens of my knives after years and years of use. Take a look at the sebenza, much more flush against the tang and it will stay there for almost ever.

Sebenzas carburize the lock face which is part of the reason that the lockup hardly moves. You are looking at the wrong dimension. You are correct that not only a tiny corner should touch. What is supposed to touch is the bottom of the lockbar to the bottom of the blade tang.

It is easier to show with a picture. Look at this well worn lockup on my HD7. Despite going all the way over the lock still is holding up great with zero lock rock. See how at the bottom of the lock it is touching and if you look up (closer to the detent) there is a little space forming a very narrow V shape. This is a correct lock geometry. When one says the corner should touch they are referring to how the bottom of the V touches and the top leaves a little bit of space. Incorrect would be if the lock fit flush and there was no little V shaped space.

If we look at the tang you can see how the lockbar is leaving a mark at the bottom of the tang. This is what we mean by “the corner” touching. They found that lockups that feature this V shape are less likely to develop lock problems. Notice the little black mark.

I am no lock expert but I have seen radiused tangs that work as well as diagonal cut tangs that work. I know Strider was having locks that wore over very quickly and developed lock rock due to their radiused tangs. (He even tried at one point to claim the knives were supposed to develop lock rock, if you were a real operator you would appreciate it) However that was something with poor lock geometry because there are many designs that use radiused tangs that aren’t prone to lock rock.

That said the trend towards everyone wanting early lockups is a fairly new thing. At one point early lock ups were not considered a necessity. If you look at the early Emerson framelocks they all seem to have locks that wore right over quite quickly but they don’t exoerience lock rock. Mine is all the way over but you can tell by the way the lock would have to continue to wear that the knife is going to lock up rock solid for years to come.

There are lots of lock geometries that can work and probably is no one right answer or “best” lock geometry. That said I know I have heard many times that lockups that don’t form that V shaped space are highly problem prone.

 

[Mick_1KRR]

Sebenzas carburize the lock face which is part of the reason that the lockup hardly moves. You are looking at the wrong dimension. You are correct that not only a tiny corner should touch. What is supposed to touch is the bottom of the lockbar to the bottom of the blade tang.

It is easier to show with a picture. Look at this well worn lockup on my HD7. Despite going all the way over the lock still is holding up great with zero lock rock. See how at the bottom of the lock it is touching and if you look up (closer to the detent) there is a little space forming a very narrow V shape. This is a correct lock geometry. When one says the corner should touch they are referring to how the bottom of the V touches and the top leaves a little bit of space. Incorrect would be if the lock fit flush and there was no little V shaped space.

If we look at the tang you can see how the lockbar is leaving a mark at the bottom of the tang. This is what we mean by “the corner” touching. They found that lockups that feature this V shape are less likely to develop lock problems. Notice the little black mark.

I am no lock expert but I have seen radiused tangs that work as well as diagonal cut tangs that work. I know Strider was having locks that wore over very quickly and developed lock rock due to their radiused tangs. (He even tried at one point to claim the knives were supposed to develop lock rock, if you were a real operator you would appreciate it) However that was something with poor lock geometry because there are many designs that use radiused tangs that aren’t prone to lock rock.

That said the trend towards everyone wanting early lockups is a fairly new thing. At one point early lock ups were not considered a necessity. If you look at the early Emerson framelocks they all seem to have locks that wore right over quite quickly but they don’t exoerience lock rock. Mine is all the way over but you can tell by the way the lock would have to continue to wear that the knife is going to lock up rock solid for years to come.

There are lots of lock geometries that can work and probably is no one right answer or “best” lock geometry. That said I know I have heard many times that lockups that don’t form that V shaped space are highly problem prone.

Yep agreed, and fully aware of all the lock treatment done by CRK, locks are my weird OCD obsession so i've made an effort to monitor and test them for years. And yes that corner you are pointing out is the correct corner in this lock wear scenario, my explanation was more for those who might be thinking the corner in question is the small Strider type corner that you see more in a front facing view.

PS. Just re-read the part about having to be an operator to appreciate it...

 

[Lapedog]

Sebenzas seem to sit fairly flush. I imagine this is possible due to their extremely exact tolerances.

Its harder to capture because the carburized lock doesn’t leave as distinct a mark on the tang. However even here we can see the wear is mostly at the bottom.

Here is a Spyderco Southard tang, featuring a radiused tang cut. Once again wear is at the bottom.

 

[Lapedog]

Yep agreed, and fully aware of all the lock treatment done by CRK, locks are my weird OCD obsession so i've made an effort to monitor and test them for years. And yes that corner you are pointing out is the correct corner in this lock wear scenario, my explanation was more for those who might be thinking the corner in question is the small Strider type corner that you see more in a front facing view.

PS. Just re-read the part about having to be an operator to appreciate it...

I definitely think that overly radiused tangs are part of the problem. If the tang forms too much of a part of the circle (so it would be a smaller circle) then that seems to lead to the major issues. Radiused tangs need to be very gently curved and only form a tiny section of what would be a huge circle.

I imagine radiused tangs are probably harder to get right.

 

[Mick_1KRR]

I deinitely thing that overly radiused tangs are part of the problem. If the tang forms too much of a part of the circle (so it would be a smaller circle) then that seems to lead to the major issues. Radiused tangs need to be very gently curved and only form a tiny section of what would be a huge circle.

I imagine radiused tangs are probably harder to get right.

Yep that's it, too much radius is just asking for lock rock later on, because the lock bar will not follow that radius as the arc becomes too great for the lock bar to keep up with. The lock bar ends up just slipping up and down the radius ramp after a while. I'll say my favorite radius tang that is done right is the Spyderco Military, it has just enough to match the natural wear arc of the lock bar travel. Used mine for a decade and even as the lock bar has slightly settled into the arc i've never had any significant wear or any lock rock (and i literally check daily..)

 

[mbkryan]

I've noticed that with some titanium frame locks or titanium liner locks that there will be lock stick when they are clean, but the stick goes away if you keep feeding them graphite and keep using them. My Emerson is like this. Zero lock stick until I clean and/or lube it, then terrible lock stick for about a week.

 

[gunfixrjoe]

Hahahahaha......Operator........hahaha

 

[marrenmiller]

Let's back this truck up a bit for a second. This is true but I think this point needs clarification. The lock bar isn't supposed to only contact by a tiny tip on the very corner of the locking bar, ever seen what happened to Strider when they used to use this geometry with their radius tang? That's why Chris Reeve knives have later lockup, because more of the lock bar is sitting slightly more flush against the tang adding stability and LESS wear on the lock bar it's self. Striders tiny edge contact point made the lock bars wear out insanely fast, we are talking a few months and they had lock rock. It's simple, the smaller the contact point the high the rate of wear will be, little surface area VS big surface area - big surface always wins. The lock bar doesn't need to be 100% flat against the tang, but a bit more that the tiny edge should be there. That's why you see 15-20yr old Sebenzas that have lock bars settled in almost to were they are dead flush with the tang and almost stop wearing for good. The mating surface is big and stable which reduces the wear rate significantly. Seen it on dozens of my knives after years and years of use. Take a look at the sebenza, much more flush against the tang and it will stay there for almost ever.

Now this Strider has the wrong kind, only the very edge wearing against that big radius tang. The huge radius caused that tiny tip of the lock bar to always be the part touching it, and they worse out quick smart, hence why strider changed their lockup geometry in recent years fixing the issues with wear and lock rock.

Strider's history of problems seem to be the result of the tang geometry not matching up with the lock bar, which you can see clearly from the picture you posted. The radius of the tang cut is completely wrong.

The single point of contact isn't the problem here. As evidence of this, look at how CRK uses a single point of contact on all of their knives with the ceramic ball lock interface.

 

[Lapedog]

Strider's history of problems seem to be the result of the tang geometry not matching up with the lock bar, which you can see clearly from the picture you posted. The radius of the tang cut is completely wrong.

The single point of contact isn't the problem here. As evidence of this, look at how CRK uses a single point of contact on all of their knives with the ceramic ball lock interface.

On my Inkosi the wear is actually opposite. Rather than the tang wearing away the lockbar, the ceramic ball wears a little groove into the tang.

 

[Mick_1KRR]

Strider's history of problems seem to be the result of the tang geometry not matching up with the lock bar, which you can see clearly from the picture you posted. The radius of the tang cut is completely wrong.

The single point of contact isn't the problem here. As evidence of this, look at how CRK uses a single point of contact on all of their knives with the ceramic ball lock interface.

The only reason the single point of contact is not an issue on the inkosi/umnumzaan etc. is because the ceramic ball on CRK knives is harder than the actual blade tang, the wear is on the tang. The single tiny edge point of contact is still an issue with knives that use untreated titanium lock bars.

 

[bhyde]

On my Inkosi the wear is actually opposite. Rather than the tang wearing away the lockbar, the ceramic ball wears a little groove into the tang.

Material isn't being abraded away as much as it's being moved and compressed under the force of the ceramic ball.