Umnumzaan Pivot Construction vs Sebenza Pivot Construction

MostMenAreRuthless

MostMenAreRuthless

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Sep 27, 2011
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One of the main reasons I strongly gravitated towards a Sebenza was the construction of the pivot using the bushing system. The fact that there is no need to fiddle with the pivot screw to adjust the lockup, tighten up bladeplay, or adjust the centering, is proverbially "blade nirvana" for me. I am somewhat OCD about this type of stuff and the Sebenza resolves that for me. So, with that being said--why is the pivot construction on the Umnum not of the same type? I don't own one so I am not completely familiar with the construction. What I do know is that the Umnum comes with a tube of Loctite--that makes me cringe and makes my OCD flare up like a bad case of piles. Can someone enlighten me?
 
The Umnumzaan was just designed in a different direction than the Sebenza. I think they just didn't want to rehash the Sebenza design so came up with something a bit different. IMO the pivot set up is the only thing that lets the Umnumzaan down, a little. The needed use of a unique and specific tool as well as the need for loc-tite just seems a mile away from what we are all used to in a CRK product. That said it's not bad at all, it's just different from the Sebenza and frankly the same as just about every other folding knife, give or take. I have carried an Umnumzaan for a couple of years or so and have never had any problems with in any way. It's a good, simple design with few parts, good materials and works very nicely as a knife and that is all it's supposed to be at the end of the day. :)
 
FWIW I use my Um without locktite, and it has never loosened from where I set it.
 
kreole said:
FWIW I use my Um without locktite, and it has never loosened from where I set it.
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Good to know kreole. I use a little teflon tape and it has stayed put after using it for a long time. I really don't think loctite is needed. Out of all my CRK knives, the Umnumzaan is my favorite. After you get it broken in a bit, it's just perfect.

Sketch
 
I have also not used loc-tite on my Umnumzaan for a good while with out issue. The pivot screw doesn't back out enough to be much of a problem but it doesn't stay put indefinitely either. I would think teflon tape is the best solution, especially if one is going to be in a situation where having to clean the knife or disassembling it out in the field is going to be likely.
 
So the principle behind the Umnumzaan pivot is a modern approach to thread engineering using precision male and female threads combined with Loctites latest technology to get strength and rigidity in the pivot.I would recommend that you use the Loctite because it is not only to prevent it from loosening up, but just a tiny drop.We are always on the cutting edge here at C.R.K. sometimes it is not always evident to the customer,so keep asking questions.
 
If your someone that doesn't like to mess with their knives and probably won't take it apart in a while then
I think a drop of loc tite is good. For me its not a big deal to tighten the pivot with my hands every now and
then thus keeping any loc tite residue out of my knife. The threads on the umnum pivot match so precisely that any backing out of the pivot usually takes a while and its very minimal.
 
chris reeve said:
so the principle behind the umnumzaan pivot is a modern approach to thread engineering using precision male and female threads combined with loctites latest technology to get strength and rigidity in the pivot.i would recommend that you use the loctite because it is not only to prevent it from loosening up, but just a tiny drop.we are always on the cutting edge here at c.r.k. Sometimes it is not always evident to the customer,so keep asking questions.
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zing!
 
I remember hearing someone saying that the male part threads only as far in to the female part so as the blade will be without wobble and easy to open and close. Is this what chris reeve is trying to say up there?
 
snowreaper1 said:
If your someone that doesn't like to mess with their knives and probably won't take it apart in a while then
I think a drop of loc tite is good. For me its not a big deal to tighten the pivot with my hands every now and
then thus keeping any loc tite residue out of my knife. The threads on the umnum pivot match so precisely that any backing out of the pivot usually takes a while and its very minimal.
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This is a friendly post, not an argumentative post. :) Based on my experience with many Benchmades and a few others knives, this general sort of pivot often seems to back out, and sometimes at very inconvenient times. The unusual tool needed to tighten (or loosen) the Umnu pivot is not something that's likely to be around (Murphy's Law applies...), so I did use Loctite on my first Umnu and will use it on the one I just bought.

Thinking about this as I type, the problem of the pivot screw backing out has almost always occurred (for me) with Benchmade knives. I wonder if there is something different about either the threads of the quality/precision of the male/female fit...?
 
No, the thread is deeper than the width of the blade, washers etc. You can tighten it enough that it's too tight to move the blade. The thread is cut very precisely though and is long so there is very little play in the thread and it's easy to find the sweet spot. Using loc-tite holds it in place and helps take up any slack.

MiG Angel said:
I remember hearing someone saying that the male part threads only as far in to the female part so as the blade will be without wobble and easy to open and close. Is this what chris reeve is trying to say up there?
Click to expand...
 
It interests me why someone would spend so much money on a knife and not follow the manufacturers recommendations but it is your money.
 
Thanks for your insight Mr. Reeve. Would you mind sharing with us the consequences of not using loctite. Besides the possibility of loosening up the pivot, is the pivot or other part of the knife endangered of being damaged by not using it? Will the pivot fail or the threads possibly strip out after hard use? I'm trying to wrap my mind around this one and know you have researched it and have a reason. I just can't grasp it yet.

On another note. Is the reason you recommend purple grade loctite to keep from damaging the prongs on the derlin tool? I have not been able to find purple loctite in any hardware stores and it seems to be only available online. Any chance a drop of blue loctite will work?

Thanks for your presence here. I acknowledge your many years of expertise in this field and I'm just eager to learn.
 
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I have had my umnumzaan for a few years and I have never had a problem with the pivot, nor have I received or used any loctite on it. I was unaware that it was recommended, but nonetheless, I have not found a need for it on mine. That does not mean that there will never be a need for it on others. I think the pivot on the umnumzaan is rather ingenious despite needing a specialized tool. When paired with the delrin tool, it likely ensures that you do not overtighten the mechanism to the point of thread stretch or failure.(I seriously doubt that you could apply enough force in this small of an area with the tools given to do much, if any damage to those threads) The tool will simply break before that happens. Easier and cheaper to replace the tool than the pivot. Secondly, the larger surface area being covered in the front, or the business end of the folder helps to ensure that the strength of the pivot and or the blade is held as securely as possible and where it is needed the most. I cannot imagine what it would take to make that pivot fail. CRK effectively went from 3 screws down to two. Albeit, the pivot on the Umnumzaan isn't likely cheap to make considering that it looks to be 2 lathe operations and one mill operation per side.

These are my opinions anyway :)
 
My Star-Tac Umnumzaan wouldn't loosen out on me but it was possible to loosen and tighten it with just thumb pressure on both sides... it's just a drop of loctite and the grade they use isn't even that strong, it can be undone pretty much as easily as a tight screw can.

I took it apart and these things are so tightly fitted it can actually be hard just to get the pivot through the holes! Great knives.
 
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