Sebenza 31 Lock Rock?!

[rileybassman1]

Well, this has been a puzzle to figure out this 31. Lol.
So I decided to break down my 31 and give it a great cleaning...for the 6/7th time? I cant even remember.
At the advice of rileybassman1 I decided to tighten the screws in different orders and managed to get it together with the pivot tight. It was still very tight to open tho. Just not as bad as before...and the terrible lock flex was still there.
Then I had to take a drive...a three hour drive, so I decided I would constantly open and close this 31 all the way down the highway. No flick open, just rolled with my thumb. I figured i would try to break it in and see if the lockup got tighter. Because as I stated in an earlier post, if i physically push the lockbar over another 1-2mm it will lock up solid. So after maybe a low count of 2000 openings and a super sore thumb...my 31 is smooth smooth smooth...the pivot screw did not loosen and is still tight...

However,

It did not fix the flex issue and now I also have side to side play. Smooth, but with all sorts of slight play. If I push the lockbar in another 1-2mm (which is almost 100% lockup) I have solid lockup, no side/side, and acceptable flex (think 21).
So with a regular roll, or even a wrist flick, this 31 will not lock up solidly.

Then I got this idea that maybe with cutting force on the blade, I could get it to lock up further...so I got a piece of hardwood and did some testing. The tests are inconclusive.
Sometimes (usually when i used the heel of the blade and a firm grip), it would go to that full solid lockup. Sometimes it wouldnt.

ETA because i accidentally hit post...

When I used force on the tip of the knife to cut the hardwood, I never achieved full solid lockup.
So very puzzling. I believe lock geometry and tolerances are slightly off...
But honestly, what do I know? Haha.

I'm wondering if perhaps CRK would put in a larger blade stop if that may help us out a little... I'm debating about reaching out to them when all this is over as well.

I disassembled and re-assembled a few more times today (and slightly stripped my pivot screw... argh... need them to open so I can get parts lol) I was able to get the same smoothness every time... I did really notice that if i tighten my pivot to full tightness, followed by the other screws... it is MUCH stiffer (but also more solid side to side)... so those of you that suffer from overly stiff pivots and the inability to get the pivot to full tightness, play with full tightening body screws prior to installing the blade.

Two interesting items of note - first the smaller washer on the lock side - I don't think it's flat... if I have it on one direction, the blade slightly favors the clip side, if I flip that washer around, the blade slightly favors the presentation side. The way it came (favoring clip side) if I tighten the pivot, work the action maybe 30-40 times, it starts to wander more towards the center... so I think something (bushing, pivot, washers?) is not even and either rotates or settles.

second item, the blade play - or what we may call lock rock - feels very similar with the blade partially open - I still get a little clicking noise - now it's not directly the same because as stated above, pushing the lockbar over further does seem to eliminate the lock rock. So... I'm wondering if the pivot/bushing are not completely to speck. I noticed some slightly uneven wear on the scales on the inside as well. I have other knives where centering seems to be dependent on the direction of the pivot.

I know we have debated about calling this lock rock vs lock bar flex... so for me in my situation, I'm getting legit click when i really try and move the blade... so I think, at least for some of us, that lock rock is what we are dealing with... and the lock "flex" is a secondary result of being a frame lock.

I wonder how many people it would take contacting them for them to be willing to try and resolve this...

 

[Sharp & Fiery]

I'm wondering if perhaps CRK would put in a larger blade stop if that may help us out a little... I'm debating about reaching out to them when all this is over as well.

I disassembled and re-assembled a few more times today (and slightly stripped my pivot screw... argh... need them to open so I can get parts lol) I was able to get the same smoothness every time... I did really notice that if i tighten my pivot to full tightness, followed by the other screws... it is MUCH stiffer (but also more solid side to side)... so those of you that suffer from overly stiff pivots and the inability to get the pivot to full tightness, play with full tightening body screws prior to installing the blade.

Two interesting items of note - first the smaller washer on the lock side - I don't think it's flat... if I have it on one direction, the blade slightly favors the clip side, if I flip that washer around, the blade slightly favors the presentation side. The way it came (favoring clip side) if I tighten the pivot, work the action maybe 30-40 times, it starts to wander more towards the center... so I think something (bushing, pivot, washers?) is not even and either rotates or settles.

second item, the blade play - or what we may call lock rock - feels very similar with the blade partially open - I still get a little clicking noise - now it's not directly the same because as stated above, pushing the lockbar over further does seem to eliminate the lock rock. So... I'm wondering if the pivot/bushing are not completely to speck. I noticed some slightly uneven wear on the scales on the inside as well. I have other knives where centering seems to be dependent on the direction of the pivot.

I know we have debated about calling this lock rock vs lock bar flex... so for me in my situation, I'm getting legit click when i really try and move the blade... so I think, at least for some of us, that lock rock is what we are dealing with... and the lock "flex" is a secondary result of being a frame lock.

I wonder how many people it would take contacting them for them to be willing to try and resolve this...

I would have to agree with all of this...and I think I even mentioned I had a cupped washer to you. And guess what? Its the little one, except my 31 is dead centered.
No idea.

 

[hoimin]

Is there anything preventing a test where you swap in a good set stop pin (collar and screws) from a 21 into the 31 to see what changes?

I don’t imagine the diameter of the stop pin changed. Maybe the shouldered recesses in the handle scales, but the collar is what matters here.

 

[rileybassman1]

Is there anything preventing a test where you swap in a good set stop pin (collar and screws) from a 21 into the 31 to see what changes?

I don’t imagine the diameter of the stop pin changed. Maybe the shouldered recesses in the handle scales, but the collar is what matters here.

I don't have a 21 but have been considering trying to track one down... if i ever get ahold of one or if I can get the hardware i'll give it a shot - curious to this as well...

 

[Sharp & Fiery]

Is there anything preventing a test where you swap in a good set stop pin (collar and screws) from a 21 into the 31 to see what changes?

I don’t imagine the diameter of the stop pin changed. Maybe the shouldered recesses in the handle scales, but the collar is what matters here.

I had the same thought on my drive. Unfortunately I wouldnt be able to test the theory until saturday.

 

[Sharp & Fiery]

This would require having the “right” 21 as well. Collars are also fitted to each individual 21. That is why we just cant blade swap any two sebenza blades. So this theory will take calipers and patience. Im actually considering making a collar myself and using a pin from a 21.

 

[hoimin]

This would require having the “right” 21 as well. Collars are also fitted to each individual 21. That is why we just cant blade swap any two sebenza blades. So this theory will take calipers and patience. Im actually considering making a collar myself and using a pin from a 21.

Well you’ve got north of 20 of’em

 

[jackghobbies]

Couple thoughts.
" so those of you that suffer from overly stiff pivots and the inability to get the pivot to full tightness, play with full tightening body screws prior to installing the blade."
Tried that, as someone suggestion to keep the stop pin (which I heard from CRK is heat hardened) a little loose while first tightening down the pivot screw.
I also noticed my washers were pretty marked up with scratches from day 1 and had a few sharp places (expected smoothness). I polished them on a very smooth strop which did help a little with blade drop.
I tried keeping them the washers the same direction, as well as flipping them 1 at a time after (re)assembly, ...
As mentioned, I tried different oil, etc..
My 2c, I believe the pivot screw, pivot bushing, and possibly the ceramic ball interface have issues and now based on comments from Sharp & Fiery I think the stop pin may also be a potential issue. Hard to say if we all have some or all of the same issues with tolerances being off.
Bottom line, a few of us have tried a *lot* of things trying to troubleshoot issues we shouldn't have too.
I'm fine with breaking in period for knife and thumb, but I agree, it would be good to narrow down commonality on when those with issues where manufactured.
My Birthdate was 02/13/2020.
p.s. I feel you on the sore thumb on open/close for hundreds of times. Same while sitting in front of the computer and binge watching a few days. Check out the thumb nail pics - lol
https://www.instagram.com/p/B-fkemll50r/

 

[kidcongo]

second item, the blade play - or what we may call lock rock - feels very similar with the blade partially open - I still get a little clicking noise - now it's not directly the same because as stated above, pushing the lockbar over further does seem to eliminate the lock rock. So... I'm wondering if the pivot/bushing are not completely to speck.

One thing to keep in mind, is when the blade is halfway between open and closed, you will have slight up/down play as all CRKs do. The pivot bushing must be slightly smaller than the blade hole or the assembly would bind as it heats up or cools down (expands/contracts). In any pivot system the does not have bearings, there needs to be a minute gap by design. This is not to be confused with the other phenomena being discussed in this thread, but if anyone starts discussing up and down blade play on a partially open/closed CRK knife I’m gonna lose my marbles. That subject has been TRULY flogged to death, and for good reason. It is not indicative of a defect.

 

[Sharp & Fiery]

Well you’ve got north of 20 of’em

Not sure I want to be accidentally mixing up parts of my perfect 21’s just to try to correct a factory mistake on my 31.

One thing to keep in mind, is when the blade is halfway between open and closed, you will have slight up/down play as all CRKs do. The pivot bushing must be slightly smaller than the blade hole or the assembly would bind as it heats up or cools down (expands/contracts). In any pivot system the does not have bearings, there needs to be a minute gap by design. This is not to be confused with the other phenomena being discussed in this thread, but if anyone starts discussing up and down blade play on a partially open/closed CRK knife I’m gonna lose my marbles. That subject has been TRULY flogged to death, and for good reason. It is not indicative of a defect.

What KidCongo says here is true. The half open play is normal and neccessary.
The play on the 31 when in lockup position is not.

 

[hoimin]

Couple thoughts.
" so those of you that suffer from overly stiff pivots and the inability to get the pivot to full tightness, play with full tightening body screws prior to installing the blade."
Tried that, as someone suggestion to keep the stop pin (which I heard from CRK is heat hardened) a little loose while first tightening down the pivot screw.
I also noticed my washers were pretty marked up with scratches from day 1 and had a few sharp places (expected smoothness). I polished them on a very smooth strop which did help a little with blade drop.
I tried keeping them the washers the same direction, as well as flipping them 1 at a time after (re)assembly, ...
As mentioned, I tried different oil, etc..
My 2c, I believe the pivot screw, pivot bushing, and possibly the ceramic ball interface have issues and now based on comments from Sharp & Fiery I think the stop pin may also be a potential issue. Hard to say if we all have some or all of the same issues with tolerances being off.
Bottom line, a few of us have tried a *lot* of things trying to troubleshoot issues we shouldn't have too.
I'm fine with breaking in period for knife and thumb, but I agree, it would be good to narrow down commonality on when those with issues where manufactured.
My Birthdate was 02/13/2020.
p.s. I feel you on the sore thumb on open/close for hundreds of times. Same while sitting in front of the computer and binge watching a few days. Check out the thumb nail pics - lol
https://www.instagram.com/p/B-fkemll50r/

That’s a pretty sucky first experience especially for a product of this price range and reputation. The upside is all these issues probably come down to two little things (maybe even one): whatever has been exacerbating some lockbars to flex abnormal amounts, and the relative thickness between your pivot bushing, washers, stop pin, and backspacer (which should come to equal). If the parts aren’t the right thickness together as a collective (or the scales aren’t dead flat), you can get a cascade of errors elsewhere (action, screws shaking loose, hardware scraping). It only takes one part in the piece to throw the whole thing off and that’s the level of precision you’ve paid for but have not currently received.

The downside is they have to be resolved by CRK to fix your knife and trace their production process shortcoming, which means a good deal of waiting and shipping anxiety.

 

[Sharp & Fiery]

That’s a pretty sucky first experience especially for a product of this price range and reputation. The upside is all these issues probably come down to two little things (maybe even one): whatever has been exacerbating some lockbars to flex abnormal amounts, and the relative thickness between your pivot bushing, washers, stop pin, and backspacer (which should come to equal). If the parts aren’t the right thickness together as a collective (or the scales aren’t dead flat), you can get a cascade of errors elsewhere (action, screws shaking loose, hardware scraping). It only takes one part in the piece to throw the whole thing off and that’s the level of precision you’ve paid for but have not currently received.

The downside is they have to be resolved by CRK to fix your knife and trace their production process shortcoming, which means a good deal of waiting and shipping anxiety.

Almost completely correct...and Im nitpiking cause im bored...:/
But... only the pivot bushing and stop pin and standoff should have identical measurments.
The washers will be ever so slightly thinner to compensated for grease and the action being too tight.

As it stands with my 31, the stepped pivot pin measures .153” and my pivot bushing is .152”

ETA: I have to double check, but Im 99% sure that my .152” pivot bushing is the same thickness of my washers and blade together. That would explain tighness of action and my pivot screw coming loose.

 

[Sharp & Fiery]

The problem with the stepped stop pin is that we just cant adjust it easily without a lathe.
The old stop pin collar could just be lapped if neccessary.

 

[hoimin]

Almost copletely correct...and Im nitpiking cause im bored...:/
But... only the pivot bushing and stop pin and standoff should have identical measurments.
The washers will be ever so slightly thinner to compensated for grease and the action being too tight.

As it stands with my 31, the stepped pivot pin measures .053” and my pivot bushing is .052”

ETA: I have to double check, but Im 99% sure that my .052” pivot bushing is the same thickness of my washers and blade together. That would explain tighness of action and my pivot screw coming loose.

Right you are on grease-space.

Does any of the stop pin nest into the scales (a tiny counter sink on the inside), or do the pin shoulders rest flush against the scales directly?

 

[bart1]

I'm so glad as I pull out and use any of my earlier Sebenzas: "P", Reg., Classic, or 21 none of the stress or problems manifest themselves.. happy in Houston.. 1st world problems,,,,I do not have a 31... might stay right where I am... still I am working on a Boomerang bladed something....

 

[Sharp & Fiery]

Right you are on grease-space.

Does any of the stop pin nest into the scales (a tiny counter sink on the inside), or do the pin shoulders rest flush against the scales directly?

Yes. It is a “stepped” pin, so both ends nestle into pre-drilled holes in both scales.

 

[bmilleker]

Almost completely correct...and Im nitpiking cause im bored...:/
But... only the pivot bushing and stop pin and standoff should have identical measurments.
The washers will be ever so slightly thinner to compensated for grease and the action being too tight.

As it stands with my 31, the stepped pivot pin measures .053” and my pivot bushing is .052”

ETA: I have to double check, but Im 99% sure that my .052” pivot bushing is the same thickness of my washers and blade together. That would explain tighness of action and my pivot screw coming loose.

Shouldn't the pivot bushing be smaller? I always thought it was the pivot bushing + washers that should equal the width of the stop pin and standoff?

Either way, your measurements would explain exactly what I was thinking. It would be great to see what a proper 21 measurements are.

I am going to send my 31 back to them to fix up. The crowned spine is not finished (low grit scratches, and it came with a large burr that I had to knock off), the pivot issues and the lock flex (which I doubt they will touch).

 

[rileybassman1]

What KidCongo says here is true. The half open play is normal and neccessary.
The play on the 31 when in lockup position is not.

Sorry I was not super clear... what I was more trying to say is that the lock rock when open feels similar to at halfway - I understand that it is necessary on the 21/31... my thought was more perhaps the specs were slightly more "tolerant" which was adding to the rock while open or requiring more lock bar tension is all

 

[Sharp & Fiery]

Shouldn't the pivot bushing be smaller? I always thought it was the pivot bushing + washers that should equal the width of the stop pin and standoff?

Either way, your measurements would explain exactly what I was thinking. It would be great to see what a proper 21 measurements are.

I am going to send my 31 back to them to fix up. The crowned spine is not finished (low grit scratches, and it came with a large burr that I had to knock off), the pivot issues and the lock flex (which I doubt they will touch).

The pivot bushing being slightly taller than the washers is why you can tighten the pivot screw to max tightness. Then the blade actually rotates around the bushing.
If the pivot bushing was shorter, then when you tighten the pivot screw...you would tighten the scales to the washers...resulting in a very tight stiff opening.
This is why people “polish” their washers.

 

[hoimin]

Yes. It is a “stepped” pin, so both ends nestle into pre-drilled holes in both scales.

Yes, the female ends nest in for sure. Does any of the stop pin shoulder sink into the scale, i.e. is the stop pin hole countersunk both on the outside (for the screw head) and on the inside (for the shoulder)? Or does the stop pin shoulder sit right against the scale while the female ends go through?