Sebenza 31 stop pin fix

T

Thetimefarm

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Jul 28, 2015
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I finally found a right handed S45V Sebenza 31 in stock and when I got it I was immediately disappointed in the fit of the parts. It felt solid but the pivot was way too tight unless you backed the pivot screw off a quarter turn. The ApostleP video pointed out that the new stop pin is a flaw in the design since it can't be lapped to the exact width of the pivot bushing like the previous design could, it's also unclear if the shoulders of the new stop pin are completely square. Solution, replace it with a 21 style stop pin, they're the same size and it fits without any modifications. When I swapped mine out it took a little honing on 2000 grit sand paper to match it exactly to the pivot bushing but it fixed my pivot issue and all the screws can now be fully tightened.

They include loctite in the box which they've previously only done with their knives that have adjustable pivots. To me this suggests the tolerances on the Sebenza 31 are not very good and they assume you'll just have to loctite the pivot in place instead of cranking it tight. I'm really not feeling the love for this 31 like I used to when I held a 21, it doesn't have that "brick s*** house" feeling that they used to have. After a few mods I like it but out of the box it just feels lacking.
 
Understood ! I recently bought a NIB Sebenza 25 birth-date Jan. 2014 and wow ! All the magic that is credited to CRK was there , 1st opening perfect if it stayed this way I would be tickled to death it got smoother no CRK thumb , yes Chris Reeve has moved in another direction so far as living up to the standards the founder implemented.
 
Idk about the tolerance claims... Mine has a birthday of June 27, 2022 which was 18 days ago. I can't confirm that the tolerances are off but I can confirm that the stop pin was 2 thou out and replacing it with one that was the right size fixed the pivot issues.
 
I’m really interested to see how this stop pin swap will work out. All crks with the ceramic lock interface have a hardened stop pin (exception with the umnumzaan). The 21 stop pin is a non hardened steel so that it would absorb more shock therefore reducing wear on the titanium lockface. Let us know how it works out.

Where did you find an extra stop pin anyway?
 
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I just took the stop pin out of my 21 and put it in my 31 lol, even unmodified it was closer to the correct size. I remeasured everything to get exact numbers, the stock 31 pivot bushing is 0.1525" wide, the stock stop pin was between 0.1535" and 0.1540" wide depending where I measured, it has a diameter of 0.2500" exactly. The stop pin bushing out of the 21 was 0.1530" wide and 0.2505" in diameter, that half a thou in diameter doesn't noticeably effect lock up at all.

It's funny you mention the difference in material since I've been thinking about that myself, even though I used a stop pin from a 21 I could make a new one from scratch out of whatever steel I wanted since I have a lathe. I was thinking 440 might work well since it can be hardened quite high while maintaining impact resistance. I don't know much about heat treatment so I'd need to find someone to do it for me and maybe give me a little info on how much the dimensions will change in the process. I'm planning on swapping the 21 pin back (hopefully) long before the harder lock interface can effect it.
 
Issues like this are why I always prefer floating stop pins. I don't want the stop pin to affect the pivot at all.
 
Random Dan said:
Issues like this are why I always prefer floating stop pins. I don't want the stop pin to affect the pivot at all.
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What exactly is a floating stop pin again? I found a couple threads about people saying they like it but they didn't describe it. It's just where the stop pin is press fit into the liners/frame instead of screwed in right?
 
LimpCroissant said:
What exactly is a floating stop pin again? I found a couple threads about people saying they like it but they didn't describe it. It's just where the stop pin is press fit into the liners/frame instead of screwed in right?
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Yes, pretty much. Press fit like what you see on the spyderco para3 and shaman just to name a couple. But the inkosi also has a floating stop pin which is screwed on one side of the hande and just sticks out the other side.

They don’t do anything to tighten the two handle slabs together, removing one variable when tuning a knife pivot action.

I personally don’t have a preference either way, they both work for me.
 
Dudleyd said:
Yes, pretty much. Press fit like what you see on the spyderco para3 and shaman just to name a couple. But the inkosi also has a floating stop pin which is screwed on one side of the hande and just sticks out the other side.

They don’t do anything to tighten the two handle slabs together, removing one variable when tuning a knife pivot action.

I personally don’t have a preference either way, they both work for me.
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I see what you mean on the Inkosi. I've never noticed that before, interesting. Yea, I suppose that's cool for getting rid of that variable like you said. I've had many knives in both styles and I don't really have a preference one way or the other either. I've never had an issue with a screwed in stop pin that I can remember.
 
The knife will break in. It's not necessary to alter the parts. I've had a shit ton of 31s and they are all stiff out of the box but smooth out with use. Thread locker is not used on the 31 to make up for slop in pivot tolerances. The stop pin is hardened, which means that it does not absorb the shock of opening. Thus, the pivot and stop pins crews, even when adjusted correctly, can back out under the influence of the vibration. This is different from a well adjusted 21, but the trade off is a stronger and longer lived locking mechanism and a stop pin that does not deform. Personally, I like both the 21 and the 31 for different reasons. One must appreciate the subtleties of engineering.
 
I mean I respect the engineering of most CRK products but this just feels like a poor mash up of various features they've implemented in other knives. Any changes that have occurred seem like attempts to cut out human intervention in assembly, which is fine if you're ok with a less expensive knife with good tolerances that needs some break in time. However that's not really what I or a lot of people think a Sebenza is supposed to be, which is why 25 is kind of a dirty word in some circles. They need people who know what they're doing assembling them and tuning them at the factory so they don't have any issues or a break in period where it's unpleasant to use. What you're saying about the loctite may be correct, I don't have any good evidence to back up my claims about the pivot accept the sample size of one I have. I currently don't have any on the screws so we'll see if they back out with the old stop pin design in place. I do know that on my knife it was extremely convenient to get it in the box when I couldn't tighten the pivot all the way... that's all I'm saying.
 
When Chris was there and even after, the tolerances were very tight. Watch the shop tour and see it was nearing overkill at that point.

If Tim tightened tolerances even more (laughs) on the 31... There is your answer. Tim got everything too tight. Also, were 21's coming in with worn locks often enough to warrant the ceramic lock?

Sorry, all that was to say that the 31 is likely not in any noticeable or measurable way more precise in construction. I don't see how with the stepped stop pin and ball fitment.

Background: 20+ lefty 21's collected over 15 years. Zero 31's. I just don't see it. I'm biased.
 
I'm not an expert, but I wonder if the perception of pivot tightness on the 31s has something to do with increased detent pressure exerted by the larger ceramic ball. I had inkosi like that, too. Right now I'm holding a plain 31 that drops free today but was quite stiff when new. I suspect that the detent pressure relaxes ever so slightly after a break in period. If I were blindfolded I would not be able to differentiate between this 31 and a 21 if action were the only factor. Anyway, I doubt the tolerances changed much when they switched to the 31. The washers are still precision lapped to match the stop pin.
 
Modernflame said:
I'm not an expert, but I wonder if the perception of pivot tightness on the 31s has something to do with increased detent pressure exerted by the larger ceramic ball. I had inkosi like that, too. Right now I'm holding a plain 31 that drops free today but was quite stiff when new. I suspect that the detent pressure relaxes ever so slightly after a break in period. If I were blindfolded I would not be able to differentiate between this 31 and a 21 if action were the only factor. Anyway, I doubt the tolerances changed much when they switched to the 31. The washers are still precision lapped to match the stop pin.
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Have you disassembled it yet? Mine was fine out of the box but the first time I put it back together the blade would barely open unless I backed off the pivot screw a little.
 
Thetimefarm said:
Have you disassembled it yet? Mine was fine out of the box but the first time I put it back together the blade would barely open unless I backed off the pivot screw a little.
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Check for blade play and a pinched washer. If it was good from the factory it should only get better imho
 
I have taken my 21's apart many times over the years so I'm pretty good at getting everything lined up right. I put the pivot screw in last so that I can test the action before I torque it down specifically so I don't pinch washers, neither of them look damaged and I had the pivot torqued pretty tight. On all my previous 21's you could assemble them without the pivot screw and they would operate like normal, then you could put the screw in and tighten it all the way down and it would feel the same. That's how good the tolerances were, but it's just not the case with this knife, you have to adjust the pivot and potentially the stop pin screws to get a good action when reassembling. Like I said out of the box the knife felt fine I just took it apart to take out that rattly lanyard pin. When I put it back together like a 21 and tightened everything up the knife didn't open well at all, I nearly needed two hands to do it.
 
Sorry didn’t mean to insult. I have a 21 that messes with me. Everything lines up and looks fine but pivot bushing isn’t through last washer and slight blade play is how I can tell. My other 12 crk go together like nothing. Just trying to help
 
No offense taken I just wanted to flash my Sebenza credentials for a second, it makes it feel like all the time and money I've put into knives was worth it for internet points.
 
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