Umnumzaan o-rings

makariotes

makariotes

Joined
Sep 9, 2014
Messages
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I am sure there is a thread about this somewhere already, and if there is I apologize, but I got an Umnumzaan that had the orings kind of mushy, or maybe spongy is a better word, they went flat as I pushed them with my finger; I had never seen that in the other ones I have; does anyone know what they are made of?
Some kind of rubber I'm sure, maybe buna? It beats me. I was too lazy to call CRK to ask, and to order replacements; so after some measuring I found out that an -006 would fit in the grooves perfectly, so I bought some viton orings a couple of days ago, and they came in the mail today.
Man what a difference!! The blade makes absolutely no noise when I flick it open, nor when I close it; the only thing I hear is the lock bar falling into place when opening the knife.
Here is a picture of the old ones:
f01ef56a39a8f89c0f1b1cbfa171fb78.jpg
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And here's the new ones
02452564c3bc56003088c586f0db560d.jpg
e4be707206de590146fadc4bc3958aca.jpg


I can actually see a tiny gap between the stud and the handle when it's closed:
f43d7f2e9b8d4129589c643e186a80d4.jpg
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Anyway, I thought I'd post about this and find out if any of you guys have tried non factory orings on your Zaans; so far I like these a lot, they actually do work as shock absorbers; I guess that was the intent of the design but never really felt it work before.
I'd love to hear what you guys think, I'm sure I'm not the first guy doing this, maybe I should have used original parts but these were .04 cents each and they work awesome. Plus viton is some pretty tough stuff. What sayest thou?
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Thanks for the info, as I will have to replace mine someday - perhaps.
 
From ChrisReeve.com: "The thumb lug doubles as the stop pin, ensuring a solid lockup. Around the lug is a polyurethane o-ring that acts as a shock absorber to cushion the impact of the lug against the handle. Never wishing to copy other designs without giving credit, Grant and Gavin Hawk originated the shock absorber concept in one of their many innovative designs. We appreciate their consent for Chris to use this adaptation of their concept."
 
SurfisLove said:
From ChrisReeve.com: "The thumb lug doubles as the stop pin, ensuring a solid lockup. Around the lug is a polyurethane o-ring that acts as a shock absorber to cushion the impact of the lug against the handle. Never wishing to copy other designs without giving credit, Grant and Gavin Hawk originated the shock absorber concept in one of their many innovative designs. We appreciate their consent for Chris to use this adaptation of their concept."
Click to expand...

Hey thanks, I don't know how many times I've read that and never paid attention to the material, so polyurethane it is. :)
 
I have the viton rings as well and they are a little more firm and quiet than the original rings. Seems like they may last longer, and they cost almost nothing anyway so I have a lifetime supply.

The only slight negative is that I notice the blade does not rest as deeply into the handle when the knife is closed. It feels like is might be possible to snag the tip and open the knife or accidentally puncture something. It hasn't happened to me, it just looks like it might.
 
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krelldoggy01 said:
I have the viton rings as well and they are a little more firm and quiet than the original rings. Seems like they may last longer, and they cost almost nothing anyway so I have a lifetime supply.

The only slight negative is that I notice the blade does not rest as deeply into the handle when the knife is closed. It feels like is might be possible to snag the tip and open the knife or accidentally puncture something. It hasn't happened to me, it just looks like it might.
Click to expand...

You bring up a good point, if you get the wrong size o ring it changes the way the lock engages, it engages earlier, and also the detent ball doesn't fall all the way into the hole in the tang; just got to be careful with the oring size; these are working great for me, and you are correct, viton lasts a long time and withstands very high temperatures as well as many chemicals, you probably already knew that. As always, Chris Reeve thinks about everything, and if he decided to use what is currently being used is because it is probably the best option for this particular application, I don't doubt for a moment that he considered using viton.
There is nothing wrong with the current orings being used by CRK, actually I think they should remain original if possible, I changed them because the ones I had in the knife I got were deteriorating, which leads me to believe that they were changed to another material by a previous owner, because I haven't seen this happen with my other zaans.
 
Pretty sure I have the right size, its just that the viton is a little firmer that the original. The lockup (and detent) works great but with almost no sound at all.

makariotes said:
You bring up a good point, if you get the wrong size o ring it changes the way the lock engages, it engages earlier, and also the detent ball doesn't fall all the way into the hole in the tang; just got to be careful with the oring size; these are working great for me, and you are correct, viton lasts a long time and withstands very high temperatures as well as many chemicals, you probably already knew that. As always, Chris Reeve thinks about everything, and if he decided to use what is currently being used is because it is probably the best option for this particular application, I don't doubt for a moment that he considered using viton.
There is nothing wrong with the current orings being used by CRK, actually I think they should remain original if possible, I changed them because the ones I had in the knife I got were deteriorating, which leads me to believe that they were changed to another material by a previous owner, because I haven't seen this happen with my other zaans.
Click to expand...
 
Krelldoggy said:
Pretty sure I have the right size, its just that the viton is a little firmer that the original. The lockup (and detent) works great but with almost no sound at all.
Click to expand...

Yeah that is my experience also; isn't awesome how silent it becomes? I just love it, you really have to feel it to believe it.
Then on the other side I love the sound of my 25 when I flick it open; which is almost impossible not to do when the pivot is adjusted just right.
Anyway, the Umnumzaan is an amazing knife, everything about it is very unique. Thanks for your reply Krelldoggy.
 
Great info makariotes. I was looking them up to bookmark them and it's asking me about inside/outside diameter, nominal width, ect. Any insight on this?
 
Judge Luco said:
Great info makariotes. I was looking them up to bookmark them and it's asking me about inside/outside diameter, nominal width, ect. Any insight on this?
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Yeah, it's kind of confusing how they did the numbering for orings, as long as you get an -006, (that is dash zero zero six) they should fit; it took a little measuring, here is the info just in case:
ID: .114 plus or minus .005
OD: .250
Width: .070 plus or minus .003

Or ID is 1/8 and OD is 1/4, but don't get confused and just get a -006, the SAE numbers are in inches and o-ring size is determined by the AS568A spec, and so on. And the sizes are called "dash" whatever, like in -006.
There are also metric sizes, but ignore those unless you like to play with conversions.

Sorry, not trying to make this a mechanical issue, or complicate it more than it needs to be; I'm a mechanic by trade so I tend to over analyze everything.
Also it is a good practice to use some silicon grease on them before you put them in.
I hope that helps.
 
Loads. I rather have more info than needed than not enough. Thanks again.

makariotes said:
Yeah, it's kind of confusing how they did the numbering for orings, as long as you get an -006, (that is dash zero zero six) they should fit; it took a little measuring, here is the info just in case:
ID: .114 plus or minus .005
OD: .250
Width: .070 plus or minus .003

Or ID is 1/8 and OD is 1/4, but don't get confused and just get a -006, the SAE numbers are in inches and o-ring size is determined by the AS568A spec, and so on. And the sizes are called "dash" whatever, like in -006.
There are also metric sizes, but ignore those unless you like to play with conversions.

Sorry, not trying to make this a mechanical issue, or complicate it more than it needs to be; I'm a mechanic by trade so I tend to over analyze everything.
Also it is a good practice to use some silicon grease on them before you put them in.
I hope that helps.
Click to expand...
 
I've been wanting to put some colored rings on for a while. I might see if I can find some this weekend if I get out to Lowe's.
 
The number 60 posted above work great and wear in a bit over time to perfection.
I've been using them for a very long time and they've outlasted the factory rings and still look and function very nicely.

Good post. The Umnumzaan doesn't get the time that the other CRK's do in the forum and stuff like this can end up very deep in the pile, it's nice to see the info brought up every now and then for what I think is one of his best knives.
 
Interesting thread. My o rings crapped out on a few of my Umnumzaans about a year ago. They look exactly like the OPs pics. What are those o rings in post #15 made of? Hmmm, might run to the Depot tomorrow .
 
lemmuhj said:
Interesting thread. My o rings crapped out on a few of my Umnumzaans about a year ago. They look exactly like the OPs pics. What are those o rings in post #15 made of? Hmmm, might run to the Depot tomorrow .
Click to expand...

NBR (Nitrile Butadiene Rubber)
 
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