Dcdavis
Gold Member
- Joined
- Oct 13, 2018
- Messages
- 8,150
I’m taking your advice. Idk why I’ve kept following it this longTime to unwatch this dumpster fire of a thread..
I’m taking your advice. Idk why I’ve kept following it this longTime to unwatch this dumpster fire of a thread..
The blade on my 31 was off center too. I purchased mine at blade show from the CRK booth and noticed it right away. I asked them while I was there about it and they said it wouldn't affect the performance but I could send it in if I wanted the washers refit. A little lame for a $500+ knife but the sebenza is still one of my favs.Well heck, I was in on page 1 of this thread so I might as well chime in now that I’ve been carrying a small 31 almost daily for 2-1/2 months….
Sample size = 1, so take it FWIW.
My knife has some lock flex.. It doesn’t feel like the lock going to slip or fail, at all, but it’s more noticeable than my other CRK’s when I’m bending it over a table.
So I don’t bend it over a table and I don’t worry about it. I suppose following this thread since inception has tempered my opinion, but there it is.
My biggest gripe is a blade that’s a bit off center, not my expectation for a CRK, but it’s centered enough for Benchmade or Spyderco standards, so I decided to roll with it.
It does sound like there have been some lemons gone out over the course of this thread. I won’t deny that.
So CRK had a knife at their booth with an off centered blade, you noticed it and bought it anyway? Did they resolve the problem?The blade on my 31 was off center too. I purchased mine at blade show from the CRK booth and noticed it right away. I asked them while I was there about it and they said it wouldn't affect the performance but I could send it in if I wanted the washers refit. A little lame for a $500+ knife but the sebenza is still one of my favs.
Yes, and no. I decided it would be ok and they couldn't refit it there.So CRK had a knife at their booth with an off centered blade, you noticed it and bought it anyway? Did they resolve the problem?
This has been covered quite extensively. The ceramic ball interface introduces a pivot pointSo first of all let me apologize for beating the dead horse here.
But I wanted to comment because I have spent a good amount of time thinking about what the lock rock is caused by and what it means and I wanted to summarize my findings and thoughts because the information is spread out all over the place.
From reading descriptions (including Tim Reeve's) of the up/down play, aka lock rock or flex, it is fairly clear to me that it happens when cutout part of the lock is flexing. The cutout flexes such that when pushed to the point of breaking, it forms a little elbow stick out to the right (on a right handed knife gripped cutting edge down). This is what Tim describes happening when he intentionally broke the lock with a hammer.
The 21 did not break in this manner, rather the lock just disengaged/failed with a lesser force. The 21 also flex less than the small 31. So the question is why the small 31 flexes more than others. In trying to answer this question I have identified only two relevant variables in the physical system of the lockbar:
(1) The amount of tension, or how hard the lockbar wants to push toward the non-locking scale. Great tension toward the opposite scale might cause the lockbar to want to flex more, because its resting position is more bent over. However, a stiffer bar could also cause less flex, and indeed increased lockbar stiffness/tension seems likely to be a way to mitigate lockbar flex, rather than its cause. Which leads me to the most likely true cause of the increased lockbar flex in the 31 vs 21:
(2) the angle of contact between the lock interface and the tang. If the force from the tang on the 31's ball is pushing more toward the non-locking scale than was the force from the tang on the titanium lockbar on the 21, this could also cause more flex to happen.
If I am indeed correct, and there is both greater lockbar tension and a more opposite-scale-directed force from the ceramic ball, the silver lining of this increased flex is that the lock is less likely to fail by slipping out than the 21.
Submitted in partial fulfillment of my degree in armchair sciences,
Yours truly,
Toivo
Imagine the blade being supported by three contact points that form a triangle: the pivot, the stop pin and the ceramic ball on the lock face. The large Sebenza forms a wider triangle than the small, thus providing more support for the blade. That, along with actually having a beefier lock bar, is why the large is less susceptible to lock flex. Again, most any frame lock will flex under enough load. The small 31 just flexes more. The subject of contention is whether or to what extent that actually matters.So first of all let me apologize for beating the dead horse here.
But I wanted to comment because I have spent a good amount of time thinking about what the lock rock is caused by and what it means and I wanted to summarize my findings and thoughts because the information is spread out all over the place.
From reading descriptions (including Tim Reeve's) of the up/down play, aka lock rock or flex, it is fairly clear to me that it happens when cutout part of the lock is flexing. The cutout flexes such that when pushed to the point of breaking, it forms a little elbow stick out to the right (on a right handed knife gripped cutting edge down). This is what Tim describes happening when he intentionally broke the lock with a hammer.
The 21 did not break in this manner, rather the lock just disengaged/failed with a lesser force. The 21 also flex less than the small 31. So the question is why the small 31 flexes more than others. In trying to answer this question I have identified only two relevant variables in the physical system of the lockbar:
(1) The amount of tension, or how hard the lockbar wants to push toward the non-locking scale. Great tension toward the opposite scale might cause the lockbar to want to flex more, because its resting position is more bent over. However, a stiffer bar could also cause less flex, and indeed increased lockbar stiffness/tension seems likely to be a way to mitigate lockbar flex, rather than its cause. Which leads me to the most likely true cause of the increased lockbar flex in the 31 vs 21:
(2) the angle of contact between the lock interface and the tang. If the force from the tang on the 31's ball is pushing more toward the non-locking scale than was the force from the tang on the titanium lockbar on the 21, this could also cause more flex to happen.
If I am indeed correct, and there is both greater lockbar tension and a more opposite-scale-directed force from the ceramic ball, the silver lining of this increased flex is that the lock is less likely to fail by slipping out than the 21.
Submitted in partial fulfillment of my degree in armchair sciences,
Yours truly,
Toivo
Ah the distance between the pivot and ceramic ball contact point is another variable I did not consider. If I understand you correctly, it is analogous to how there is more torque in the center of a spinning wheel, then on the outer edge so the small 31 has to deal with with more torque than the larger one.Imagine the blade being supported by three contact points that form a triangle: the pivot, the stop pin and the ceramic ball on the lock face. The large Sebenza forms a wider triangle than the small, thus providing more support for the blade. That, along with actually having a beefier lock bar, is why the large is less susceptible to lock flex. Again, most any frame lock will flex under enough load. The small 31 just flexes more. The subject of contention is whether or to what extent that actually matters.
I just think it is fun to try to understand the properties of different locks. Obviously there is a minimum acceptable lock strength for a given person or application and for me the small 31 exceeds that minimum threshold, but there is still the question of by how much it exceeds it. It seems like the issue of this thread has mostly been about the aesthetics of up and down blade play, so I wanted to shift the conversation back towards performance of the lock which is more important to me.When you ask wtf they are doing they reply "I read on the internet that sebenza 31s have lock rock" then I laugh and explain to them that their using their knife wrong. Does anyone else think this is a little ridiculous?
My large Inkosi flexes just as much as my large 31 and 4 Zaans I owned.I still think that CRK should have kept the ball groove on the blade tang lockup surface. My Large Inkosi (with ball groove) exhibits no flex.
Yes, but was it the initial batch LI with the ball groove? (see pic) It stops the "creep" of the ball sliding on the blade tang.My large Inkosi flexes just as much as my large 31 and 4 Zaans I owned.
They were all 2020 or 2021.Yes, but was it the initial batch LI with the ball groove? (see pic) It stops the "creep" of the ball sliding on the blade tang.
My 2016 small Inkosi does not have the ball groove as well as my 2022 Large Inkosi. Both show less “lock rock” than my small sebendza 31, an amount of movement I would consider insignificant. I don’t think the ball groove does much and that’s probably why it’s been eliminated.I still think that CRK should have kept the ball groove on the blade tang lockup surface. My Large Inkosi (with ball groove) exhibits no flex.
What it does is prevent the lockbar from vertical motion in lockup. Without the ball groove, squeezing the grip will induce lockbar flex wherein the ceramic ball is moving on the blade tang. While it isn't much of an issue, I personally prefer the more solid feel of the version with the ball groove - it doesn't move when gripped firmly.My 2016 small Inkosi does not have the ball groove as well as my 2022 Large Inkosi. Both show less “lock rock” than my small sebendza 31, an amount of movement I would consider insignificant. I don’t think the ball groove does much and that’s probably why it’s been eliminated.
IMHO the only way you're going to have perfect non moving in any direction blade is with a fixed blade knife.