Detent rock

[sharp_edge]

I know this topic has been discussed multiple times but it appears the cause(s) has/have not been unanimously agreed upon, so I would like to see a bit more discussions as well as offer my thoughts.

First off, detent rock here refers to the slight up-and-down blade play when the blade is in fully CLOSED position. The detent rock can often be audible if the knife is shaken. When this problem presents, usually up-and-down blade wiggling can also be felt when the blade is at any position between fully closed and fully locked (note: the blade is actually not traveling when wiggling).

It seems many people attributed the problem to the detent hole (on the blade) being too large, although I have never seen any knife maker confirmed that. I also would like to counter-argue that if that is the cause, why the blade still wiggles up and down when the detent ball has already gone out of the detent hole?

I suspect another possible cause can be that the detent ball itself is wiggling/rolling in the cage (that is, the thing that hosts it). I understand the detent ball is press fit into the pole/lockbar and based on the discussion in this old thread, on some framelock knives the detent ball does roll. If that is the case, a not properly press fit detent ball can indeed wiggle, thus resulting in the problem of "detent rock" and in some cases, the detent ball can fall out.

Part of my reasoning is from my experience of three ZTs with the problem of detent rock. They were all fixed by KAI warranty and I did not see either the lockbar or the blade was ever replaced. I did not know whether it is the detent ball that was replaced (and it would be very difficult to tell given its size).

Your experiences and/or thoughts?

 

[blades&wrenches]

As far as rocking when closed, I’ve always heard it’s an issue of the ball not correctly fitting into the hole, whether it be the ball is too small or the detent hole is too large. Usually can be remedied with a slightly larger detent ball.
Rocking when partially open is typically the result of tolerance between pivot and blade, from what I understand.

 

[Mo2]

Some of my zt's exhibit this too. Its annoying it's so common apparently. I don't want to send knives into warranty for anything as I want them to be quality. Argh. Frustrating.

In any case my 0850 is the worst of the bunch. I would suggest it's detent hole size and also weak lockbar pressure on this one.

I've seen Jake from knife nuts podcast do knife surgery on his Instagram stories where he modified the detent hole and replaced the detent. Was pretty good watch. Guys got some skills.

 

[REK Knives]

When this problem presents, usually up-and-down blade wiggling can also be felt when the blade is at any position between fully closed and fully locked (note: the blade is actually not traveling when wiggling).

I have repaired a lot of blades w/ detent rock and can confirm that detent hole in the blade tang it is either because the hole is in the incorrect location or it's too large. I have never felt what you are describing above (wiggling when it's at any position) on the knives I have repaired.

It seems many people attributed the problem to the detent hole (on the blade) being too large, although I have never seen any knife maker confirmed that. I also would like to counter-argue that if that is the cause, why the blade still wiggles up and down when the detent ball has already gone out of the detent hole?

It doesn't in my experience. If this is present then I believe it's another tolerance issue, but not the detent ball. The detent ball is pressed into the lockbar and can't roll or move (if it could, it would fall out).

 

[sharp_edge]

I have repaired a lot of blades w/ detent rock and can confirm that detent hole in the blade tang it is either because the hole is in the incorrect location or it's too large. I have never felt what you are describing above (wiggling when it's at any position) on the knives I have repaired.



It doesn't in my experience. If this is present then I believe it's another tolerance issue, but not the detent ball. The detent ball is pressed into the lockbar and can't roll or move (if it could, it would fall out).

Thank you. I agree it is possible that a knife can have the issue of detent rock and the other issue as I described.

I'm just curious if the detent hole is too large, how to fix it? It sounds more material (steel?) will have to be put into the hole to make it smaller.

 

[REK Knives]

you either have to install a larger closing blade stop, a larger detent ball, or last/worse case, drill the hole out and plug it, then re-drill a new detent hole in the proper location.

 

[nwmetalbug]

My 0392 does this. I think the pivot/blade clearance is slightly over spec so you feel just a little wiggle until it locks. no problem to me. just to clarify it doesnt do it open or closed just in between.