What determines the smoothness of a folder?

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kkim0229

Joined
Dec 6, 2006
Messages
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Hi folks!

I own a small classic Sebbie and a Benchmade Axis folder. Here I'm going to compare those two in my perspective. I'd love to see a lot of feedback on my analysis!

So, recently I read about Axis lock mechanism and saw how smooth it can be. I got hooked and had to check it out. Axis lock is great. Let me just lay it out there. Wow smooth, fast, and a lot of fun factors (plain joy to flick open and close). Then I hold the Sebbie, and it almost feels rough. Talking about smoothness; I believe its major source of friction is NOT the pivot (handle-washer-blade tang interaction), but the lock bar (detent ball-tang interaction). I wrote about this previously. Just hold the lock bar so it doesn't touch the blade, and your Sebbie's blade will drop like guillotin on your thumb. In other words, lock bar tension is the inherent variable of the action of Sebenza. Well, some folks prefer the "molasses" feel of the Sebenza as opposed to almost slippery action of, say, an Axis folder (I am putting Benchmade's Axis, Spyderco's ball bearing lock, and SOG's Arc lock in the same category here because they work similarly) due to weaker spring(s) pressing parts against the blade tang. Lock bar is certainly stronger than the omega spring in Axis or the coil spring in ball bearing lock. I will not consider other types of locks such as lockback which are not meant to be operated one handed.

Maybe you noticed by now, but I enjoy opening and closing knives (a habit from flipping balis). So any folder I acquire, I quickly understand how the knife holds up to repetitive opening and closing. Has anyone noticed that after several cycles (I'm talking around 50 minimum) of opening and closing a Sebbie, it suddenly becomes really rough? Strangely, if you put it down for an hour or two and open it later, it's smooth once again. No, lubing the pivot is not the answer, because if you hold the lock bar open the blade still moves free. My take on this is that the detent ball has become hot from constant rubbing against the tang and expanded to make the action rough. Once it cools down, everything's back to normal.

So in my case, constant smoothness is a major deal maker/breaker. I appreciate the simplicity and reliability of Sebenza, but I also appreciate the mechanical ingenuity of Axis that makes cycling it so enjoyable. After all, I perceive my folders as more than simple cutting tools. I take them as toys.

So my search goes on: thrust washers are used by Larry Chew and RJ Martin. Sealed bearing is employed by Brad Duncan. IKBS is used by Korth, DDR, Les Voorhies, Todd Begg, and probably more I don't know of. However, these are all remedies for pivot friction. More friction is due to the liner/lock bar detent ball scraping against the blade tang, and if the particular folder is a framelock folder like Sebbie, I can't see its action being smooth after hundreds of cycles. Maybe I'm clinging to the theoretical assumptions, since I, for sure, have not opened and closed folders made by the custom makers mentioned above hundreds of times back to back.

And recently I stumbled upon G&G Hawk's lock design. No part scrapes against the blade tang while opening/closing. Basically the blade opens like it's floating in the air. Ingenious! Naturally the lock is very wear resistant. Simplicity/reliability issue aside, I view this lock as the best lock design ever developed so far. Well, their knives are priced accordingly high too. And the styling is just not my cup of tea.

Back to comparing Sebenza and Axis. While I really liked the action of Axis, I feel compelled to say the precision machining of Sebenza is yet not matched. For example, Sebbie's blade is so perfectly centered with tight tolerances, you can't get it to even touch the handle scales with reasonable force. With any Benchmade folder? Just give it a little nudge, it will scrape against the scales right away. I guess that's where a part of the price difference comes from. You might be nitpicky like me, or you might be not. That's a whole different issue.

Well, to sum up this meander, I guess I'm yet to find my dream knife.
What do y'all think?

Edited to add: by the way, what about button locks, what part touches the blade tang?
 
A major part of the force on the Sebbie 'ball' is the clip. Since I like my knives clipless, removing the clip has left my Sebenza much smoother and easier to work.
I hadn't thought about heat from continued opening causing an expansion pressure, that sounds reasonable.
My smoothest, easiest folder is a 'flipper' that has a very light detent in the closed position. It also has ?nylon? washers on the pivot.
Greg
 
I'll have to disagree with you Greg. I had to bend out the lock bar a little to adjust the lock strength. Simply removing the clip might have helped but not by much.
 
Cool post, kkim. It does seem like bearings rather than washers are the way to go, but it looks like even high-end folders use nylon washers. Do these hold up?
 
Twindog,

Nylon washers are less durable than phosphorous bronze washers from what I hear, which is reasonable. One is polymer, the other is metal. However, nylon washers are known to provide more slippery surface interaction.

You might be missing my point though. I own a nylon washer folder, and yes it's smooth, but only for first several cycles. Guess what! It happens to be a liner lock folder with a damascus blade. The detent ball gains heat from friction, expands, then scrapes against the UNEVEN damascus blade tang. Oh boy, it can't get any rougher than that. However, I leave it alone for an hour or two, the ball cools down and shrinks. The action is once again smooth.

Bearings, thrust washers, IKBS, you name whatever mechanism developed to reduce pivot drag. As long as the folder is a liner/frame lock, its action is bound to temporarily roughen after numerous cycles somehow proportional to the lock strength. The stronger the detent is pushed against the tang, the more friction.

Although I bet the extent differs significantly by maker/brands, I view the roughness as an inherent limitation of all frame/liner locks.

Please don't think I'm advocating against these locks though. Folders are primarily meant to lock securely and cut, not to be opened and closed over and over again which is what I do to my knives.
 
I own a nylon washer folder, and yes it's smooth, but only for first several cycles. Guess what! It happens to be a liner lock folder with a damascus blade.
Click to expand...

Would thiis happen to be a mcusta, because i noticed the same thing.
 
I kind of almost reached the same conclusion on my own. I, too, remember my last Sebenza getting 'rough' after some handling. I would get concerned, then it would be gone the next time I picked it up. I never verified the connection between the heated ball bearing and the roughness, but I suspected it.
I'm interested to hear others' thoughts on this phenomenon.

I agree about the Axis locks, as well..."Like Butta!"

A button lock has no contact with the blade, when it is depressed. For Switcblades with a button lock, this means that the action is very fast. You may want to look into button locks, for smoothness. The only problem you may encounter, personally, is that with constant opening and closing of a coil-springed auto, the heat build up will weaken the firing spring, and shorten it's life considerably. I speak from direct experience. I wore out 2 springs in 2 years, then learned my mistake, and that knife has had the same spring for 5 years, now.
 
Sebenzas come with a very strong lock bar.What I did is the sme as Kkim did..Bend the lock bar very very carefully.Do'nt over bend it cause then you will have problems.I've done this with 2 Sebenzas I have and their as smooth as any older I have except a few customs.BTW I'm sure Chris Reeve will not advise this.
 
A
button lock has no contact with the blade, when it is depressed. For Switcblades with a button lock, this means that the action is very fast. You may want to look into button locks, for smoothness. The only problem you may encounter, personally, is that with constant opening and closing of a coil-springed auto, the heat build up will weaken the firing spring, and shorten it's life considerably. I speak from direct experience. I wore out 2 springs in 2 years, then learned my mistake, and that knife has had the same spring for 5 years, now
Click to expand...
There are also button locks without the coil spring like William Henry makes.I'm sure there are others.SpeedTech made them-too bad their out of buisness.
 
Not to nit pick too much but it sounds like you guys are using the term "smooth" in the wrong way.

When you guys are saying "smooth" do you really mean less effort to push the blade around the poivot?

A knife can open smoothly but still require quite a bit of effort to push the blade open.

To me, a non-smooth opening folder would be one where the effort to push the blade around the
pivot changes, sticking a bit in places.

What determines the ease of opening a folder is how I would put the question.
 
Rich357,

You are correct in that smooth may mean the "uniformity" of friction not ease of opening. However, let me point out that the folders we typically call "smooth," let's say Sebenza for an example but any frame/liner lock folder, really don't open and close all that "smooth" by your definition. In fact, they become non-smooth opening folders exactly as you describe: "one where the effort to push the blade around the pivot changes, sticking a bit in places." My Sebenza is so smooth for a minute or two of opening and closing. Then it becomes rough and sticky. I observed this from cheaper folders to Sebenza.
 
My contribution to the "smooth" conversation involves my -$20 Cara Cara. Upon purchase I disassembled it and mirror polished all the contact points, lightly lubed with Tetra Lube and it is amazingly smooth now. Not loose at all, as a matter of fact the polish job allows me to run the knife a bit tighter without any roughness or binding, and eliminates any lateral blade play. This is of course a lockback not a liner.
On my Camillus Heat & Blaze I did the same, but really worked the detent contact area on the tang section really well with a hard felt wheel on my Dremel and now have PB washers instead of the nylon, and they are noticeably slicker. They don't however respond well at all to a tight pivot screw, as the AO just doesn't have the same follow through stroke as a thumb.

Beckerhead
 
kkim0229 said:
Rich357,

You are correct in that smooth may mean the "uniformity" of friction not ease of opening. However, let me point out that the folders we typically call "smooth," let's say Sebenza for an example but any frame/liner lock folder, really don't open and close all that "smooth" by your definition. In fact, they become non-smooth opening folders exactly as you describe: "one where the effort to push the blade around the pivot changes, sticking a bit in places." My Sebenza is so smooth for a minute or two of opening and closing. Then it becomes rough and sticky. I observed this from cheaper folders to Sebenza.
Click to expand...

I have several Sebenzas and after the initial effort to get the ball out of the detent the blade requires virtually the same effort as it moves around the pivot until it locks. However, movement is stiffer. It takes a bit more effort that most of my Benchmades. I'm sure with the right lube and plenty of opening and closing the amount of effort to move the Sebenzas blade would be reduced.

Have you taken your Sebenza apart? Are you sure you followed the right sequence when putting it back together?

The only time I've had a problem with the movement of a Sebenza blade is when I've taken apart the Sebenza and didn't put it back together per CRK's instructions.
 
Rich357 said:
I have several Sebenzas and after the initial effort to get the ball out of the detent the blade requires virtually the same effort as it moves around the pivot until it locks. However, movement is stiffer. It takes a bit more effort that most of my Benchmades. I'm sure with the right lube and plenty of opening and closing the amount of effort to move the Sebenzas blade would be reduced.

Have you taken your Sebenza apart? Are you sure you followed the right sequence when putting it back together?

The only time I've had a problem with the movement of a Sebenza blade is when I've taken apart the Sebenza and didn't put it back together per CRK's instructions.
Click to expand...


Rich,

My Sebenza is smooth. No doubt there. And I believe all the non-defective Sebenzas that make into the market are. And yes, I have taken Sebenza apart and put it together per CRK's instruction and I trust my ability to follow the instructions carefully.

Now, my point is that even the smoothest frame/liner lock folder like Sebenza, IF you open it many many times, more like a hundred+ back to back, it will become TEMPORARILY rough. I leave it alone for an hour to cool down, it's back to super smooth. Lubing, polishing or wearing in is not the issue here. This phenomena, as posted above, has been observed by other users as well. But since a knife is NOT designed to be opened and closed repetitively while you're watching TV, I wouldn't necessarily call this a defect in design. It's just a characteristic of framelocks. However, people like me who enjoy cycling their folders might as well take a note of this.
 
kkim0229 said:
Rich,

My Sebenza is smooth. No doubt there. And I believe all the non-defective Sebenzas that make into the market are. And yes, I have taken Sebenza apart and put it together per CRK's instruction and I trust my ability to follow the instructions carefully.

Now, my point is that even the smoothest frame/liner lock folder like Sebenza, IF you open it many many times, more like a hundred+ back to back, it will become TEMPORARILY rough. I leave it alone for an hour to cool down, it's back to super smooth. Lubing, polishing or wearing in is not the issue here. This phenomena, as posted above, has been observed by other users as well. But since a knife is NOT designed to be opened and closed repetitively while you're watching TV, I wouldn't necessarily call this a defect in design. It's just a characteristic of framelocks. However, people like me who enjoy cycling their folders might as well take a note of this.
Click to expand...

Ok. But, in your earlier post you didn't mention that you were opening and closing it 100+ times within a short period of time. I don't think I've ever opened and closed one of my Sebenzas that many times over a short period of time.
 
kkim0229 said:
Maybe you noticed by now, but I enjoy opening and closing knives (a habit from flipping balis). So any folder I acquire, I quickly understand how the knife holds up to repetitive opening and closing. Has anyone noticed that after several cycles (I'm talking around 50 minimum) of opening and closing a Sebbie, it suddenly becomes really rough? Strangely, if you put it down for an hour or two and open it later, it's smooth once again. No, lubing the pivot is not the answer, because if you hold the lock bar open the blade still moves free. My take on this is that the detent ball has become hot from constant rubbing against the tang and expanded to make the action rough. Once it cools down, everything's back to normal.
Click to expand...

This is a quote from my first post. I'm sorry if it wasn't clear to you. The numbers are arbitrary, I just meant a lot of cycles back to back. I never counted exactly when the action becomes rough.
 
"Well, to sum up this meander, I guess I'm yet to find my dream knife.
What do y'all think?"
------------------------------------------------------------------

Nothing like a good bali for fun opening and closing. :-)
 
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