A discussion about smoothness. Please add your thoughts.

kidcongo

kidcongo

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Jan 12, 2013
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What attracted me to purchase my first CRK was the claims of their legendary "hydraulic smoothness". I have spent a lot of time thinking about what makes them smooth playing with my knife in front of the TV, or driving. Also I use my knives a lot for EDC tasks, and am always getting fruit juice, glue, dirt, seawater, etc on them. This has led me to some personal conclusions that you may or may not agree with, but might be worthy of your consideration.

1 - I think the overall day-to-day smoothness of the knife is most greatly affected by the track of the detent ball (small ceramic detent ball on 21, and large ceramic detent/lock ball on 25 and Umnum). This is that little groove on the lock-side of the heel of the blade where the detent ball rides along. Any dried material, juice residue, or any product that washes the track clean of grease, or leaves a residue, with greatly affect the feel of the knife. To restore the knife to silky smooth I often just need to clean and grease/oil the track and it's back to perfect with no disassembly. Sometimes after cutting an orange and getting the acidic juice on the track the knife will be gritty for a few minutes, until the detent ball cuts through the residue, or some latent grease works its way back onto the track, thus fixing the problem with no effort from me.

2 - I think the "legendary smoothness" of the Sebenza comes from the use of a ceramic detent ball on steel. Steel on steel will not slide as easy (think locomotive wheels on a steel rail). A lot of focus it put on the pivots, and the special washers, and the CRK grease, but I think it's the ceramic detent ball that is the key to the legend, and why the knives seemed so much better than everything else when they were first offered. The ceramic ball also does not gall or scratch, or become pitted due to the nature of the material, so as it wears down it's surface stays smooth. I have a couple Spyderco lock-backs (Native 5 and Sage 4) and not matter how much lube is in the pivot, or how much grease or oil or whatever you put on the blade tang where the lock bar presses on it, those knives always feel a little gritty due to the steel not being perfectly smooth on either the blade or the lock bar. I also think the ceramic ball has the ability over time to cut a perfect groove in the steel because it is so hard, which is why Sebenza's seem to "break in" and get smoother over time.

Questions for those who might know:

1 - Was CRK for the first mass-produced folder with a ceramic detent ball?
2 - Did the early Sebenza's ever have a steel detent ball, or has CRK always used ceramic?

What are your thoughts on the smoothness of these knives?
 
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My umnumzaan is smooth, but the seven a classic is just way smoother. Grease, oil, or even nothing it still feels hydraulic. Umnumzaan is smooth but the hydraulic feeling is non existent.
 
I believe the bushing system and washers also have a lot to do with it. Think about how much the feel of the knife changes when you shave a little bit of the washers off. Now also imagine replacing the washers with plastic. ICK! The ceramic ball definitely adds to it as well.

One thing I do, is if the innards get gunked up from something, just running it under water and opening it and closing it fixes it right up with no need to add any grease.
 
Ive owned and handled them all.
The 21 style is the smoothest easily/regular. A unique smooth as you mentioned.
Combination of
-"Thrust washers" with the holes for less friction and holding the lube
-Detent that wears in perfectly onto the blade surface. Making a nice smooth path
-Bushing system that allows a perfect free fall of the blade when pressure is removed from the lock bar. If yours does not drop when there is no tension on the blade you can simply do a wet rub on your fine ceramics to even up to the bushing. Most will wear in anyway if it is not perfect.
My knife just seems to keep itself clean and does not gunk up, just a quick run under the water. It still holds the Christo Lube fine and is smooth as a babys bottom.

As for your questions, no clue.
But what I have found to appreciate is the perfect lock up that has not budged and just remains at about 50 percent no matter how I use it. And just a great blade grind and shape.
Sorry , back to smoothness.
 
Don't have an answer to your two Q's but i CAN tell you that my ten year old large regular (original washers) is by far the smoothest Ti frame lock that i have.
The action is truly like ice on glass :joyous:.
 
Yep, nothing like a CRK. MY 21s or the 25, in a class by theirselves.

My non-knife shooting buddies were even very impressed.
 
I think that because of two different materials being worked against each other is what causes the hydraulic motion. Because the ceramic does not produce heat when contacting another metal, it will not gall but instead cut the metal. Even though the ceramic is polished, it is still more abrasive than a smooth metal. Thus, the hydraulic feel is actually the ceramic ball cutting a path in the titanium until it seats in. I also feel that the combination of material used, tight tolerances, milling of the titanium make up a perfect harmony that make the CRK so desirable. It is for me anyway!
 
Don't forget about pressure applied by the lockbar. My the detent ball on my umnumzaan is forced against the blade with much much more pressure than my 3" XM-18, or my Socom Delta.

This being said, as smooth as my umnumzaan is to open, it will not free fall when the bar is depressed. It is still as smooth as glass though, just needs a little help.
 
I never refer to crk action as smooth, it is so much more unique than that......everything it seems is referred to as super smooth. "Hydraulic" is great description for a sebenza just based on the fact that you feel this amazing fluid like resistance, consistently and evenly. I feel "smooth and effortless" is good description for bearings as the action proves to have next to zero resistance, like a blade moving on a pivot you cannot feel. I'm not saying that either or is superior but I love the hydraulic feel of a crk forcing me to open and close them endlessly! My .02
 
my broken in Umnumzaan is smooth, but not Sebenza smooth ;) and the Umnumzaan is already smoother than a lot of other knives out there.
 
I really can't answers the questions. My large reg. from 97 and my small from 2000 both have the old flat washers and sooooo smooth. It is hard to describe, I can not feel anything or hear a sound. My Umnumzaan is smooth but not like the two old regulars. And both of them have very little CR grease in them. If I had to guess I would say it is the tolerances, sometimes it takes a while to get them reassembeled just right, everything has to be just right. You gotta love that.
 
My small is my smoothest. Could be the washer polish I did long ago.

Most people can barely tell how smooth it is, maybe something only knife hobbyists can tell. Most guys just want a fast opening blade.
 
I believe the detent on the regular, classic and 21 are all steel detent balls, explaining why Ive seen some replaced over time. the only ones using ceramic are the ti-lock, umnum and 25.
 
JPR984 said:
I believe the detent on the regular, classic and 21 are all steel detent balls, explaining why Ive seen some replaced over time. the only ones using ceramic are the ti-lock, umnum and 25.
Click to expand...

I have 4 21s and they all have ceramic detent balls, not steel. It is much smaller than the 25/umnum, which also use the ball as a lock, but are ceramic nonetheless.

The Ti-Lock does not have a detention ball. It uses a different system. Maybe you mean the pivot ball bearing system?
 
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If you watch the exquisite blade vids it discusses the detent ball on the 21s being ceramic, and they are dark Gray in colour, as all ceramic balls I have seen are.
 
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