umnumzaan disassembly, ceramic ball not moving?

zyhano

zyhano

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Hi guys,

I disassembled my umnumzaan for the first time today since it wasn't moving as smooth anymore (which by the way was still very smooth compared to any other knife I own, including sebenzas).

My ummie came with a takedown kit included (born sept 2009) which also has a nice disassembly/reassembly manual.

After cleaning I decided to take a good look with a magnifying glass and I was especially interested in the ceramic ball, since there were some posts about the strength of the ball (just answered in another post, veryyyy strong) the wear on the ball and also about the fixation of the ball.

I could not see any hard wear on the ball, or any places that were not round, but I also could only examine a small spot on the ball since I was not able to move it with my fingers. I tried, tried hard, but it wasn't rolling.

I understand that a ball in a ball detent should be rolling, else it obviously shouldn't need to be a ball. So, given that fact, I can assume that it won't move when trying that with my fingers but that it should move when making contact with the metal under some more force.

It looked like it was fixed very tightly, almost as if it was stuck, but I'm not sure about that. If the ball is so fixed that it wouldn't move, I can then vouch for it's strength and toughness since, as stated earlier, I didn't see any noticeable wear on the ball surface and I did open that little beaty a lot :thumbup:

Does anyone have the same experience or totally different? Does yours roll easily or not at all?

I'm curious about it. I guess in theory it wouldn't matter, since the blade is softer than the ceramic ball it will wear out a bit, but the ball will keep falling in the detent to prevent the blade from opening (it's primary function).

I did not take photo's but can try to make some close up shots (have to wait till daytime) if you guys want to see it. (and of course one of you dudes will now say "yeah, I'd like some pics" :D)

I took a good look at the edge too, and saw some nicks. Put it to the steel rod and after that: razorsharp again :)
 
Im almost positive that I read in one of the threads on the CRK forum in 09

that the ceramic ball is held in place with a pressed fit.

If you think about it the ball would have to be pressed to stay in place.There

wouldnt be a way to hold it place and still have the ball revolve.

If Im wrong about this Im more than willing to be corrected!
 
I read that too, but that's the whole point: why use a ball if it is not rolling. any shape would do in that case, since it's only function would be to 'snap' into the detent.


And if that's the case, probably any other shape could have been fitted better I guess. A ball is not easy to lock into place.

A rolling surface would wear slower because of continuous different contact points.

Oh, and I guess that if you pressed the ball at about 2/3 on the blade side and on the tang side, the ball could still revolve and stay in place.
Just place a tennis ball in your hands and fold your hands over it and leave out the top 1/3 to see what I mean
 
zyhano said:
I read that too, but that's the whole point: why use a ball if it is not rolling. any shape would do in that case, since it's only function would be to 'snap' into the detent.
Click to expand...

Detent balls do NOT rotate.
Not in any frame-lock or liner lock I have EVER owned, seen, held, or even heard of.
 
There is no need to rotate as the lube is supposed to shear between the frictional surfaces, like all lube does. If the ball rotated within it's pocket, then there would be an increase of tolerance that would likely increase wear on the pocket, the ball and the blade at an accelerated rate.

A ball offers some advantages: already being made so no special part needed, minimal surface contact area on blade, self centers both on the punch fit and the retention hole.

Given the application and trade offs a ceramic ball is probably the optimal solution.
 
There have been a lot of questions about the ceramic ball. It's supposed to roll around like a rollerball in a pen. It does NOT require lube.
 
When I took apart and cleaned my umnumzaan, the ball Did Not Move/Roll/Rotate. It is pressed fit and then piened slightly to move more metal around to hold it in place even more. Since the ceramic is so hard, it just basically glides over the steel blade tang. The ceramic ball is like 90RC, while the blade is say 60RC. The ball will far outlast the blade. Since its round and since the contact area to the blade is SO Small, it does not need to roll. Figure the contact area to the blade is almost like the point of a pin contaction the blade. Over time and the umnumzaan wearing into the blade tang, it will contact even more, but I think that would be quite some time down the road if it ever happens at all......But to answer your question, the ball does not move. If it does, maybe thats a problem ??? I am not sure, but most people I have spoken with on here, the ball on their zaan does not move.

I have had Zero Detent Issues. The ceramic detent holds my blade firmly in place. The knife will only open if I physically open it either by pulling the blade out or using the thumbstud to open it.
 
Last edited:
I was being facetious in post #4....the ball does not move nor is it suppose to.
 
stabman said:
Detent balls do NOT rotate.
Not in any frame-lock or liner lock I have EVER owned, seen, held, or even heard of.
Click to expand...

Yup, they never roll, they always slide over the surface.

To set it up like a ball point pen would be just too much trouble for the bother to be worth it.
 
bigmark408 said:
I was being facetious in post #4....the ball does not move nor is it suppose to.
Click to expand...

had to look up facetious on translate.google.com :)

Oke, thanks for your replies! I guess maybe my assumption was wrong. I thought it functioned like a ball bearing, with the ball rolling for smoother action.

@resuwen3: can you elaborate a bit on that? from what I looked up on ball detents (non knife related) they should be able to roll, so I feel we haven't reached a 100% certainty here
 
Amusing mix of information here. Love to add my own bit of confusion ;) ...

As I understand it, the ceramic ball is NOT designed to rotate (although due to the way it's held in place - conceivably it could). Not a problem if it does rotate, only a problem if it falls out. (lol) :) No lube needed or required.
 
Can someone who knows his ball detents / ball bearings please step in :)
Maybe someone from CRK?
 
from what I looked up on ball detents (non knife related) they should be able to roll,
Click to expand...

No offense meant but did you think about that you just wrote? Since we're talking about knives what does it matter what you read about non knives?

Further research would proobably show that rollinng detentes are not 100% in NON knife applications as well.
 
DaveH said:
No offense meant but did you think about that you just wrote? Since we're talking about knives what does it matter what you read about non knives?

Further research would proobably show that rollinng detentes are not 100% in NON knife applications as well.
Click to expand...
none taken :thumbup:. Yeah, I thought about it.
It matters in the sense that I'm interested in knife design and the mechanical principles and the practicality of their implementations. I started this discussion to learn.
No offense to you, but that's why posts like this matter to some.
 
Detents don't roll. Period. That's the real deal. Rolling would not be a good thing - more parts to break, goo up. Especially on an Umnum - the lock up wouldn't work, just roll off the tang.
 
RLR said:
Detents don't roll. Period. That's the real deal. Rolling would not be a good thing - more parts to break, goo up. Especially on an Umnum - the lock up wouldn't work, just roll off the tang.
Click to expand...
Ok, I get that, the go0ing up part is a good point:thumbup:.

but it would not necessarily be bad for the lock up right? the force of the frame is inward because it is bent. the ball rolling *might* make the action smoother, but it would not unlock by itself. It's not like a ball rolling of an angled road, there is an opposing force.

forces on the ball itself would be pointed at the frame against the direction of the bend when closed (I don't see an extra risk of breakage) or against the direction of the titanium going to the side opposite of the pivot when locked in open position. Just as it is now..

I don't want to be a smartass about it, as stated before, I'm just curious.
 
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