sebenza lock bar and tang coverage

J

JohnM

Joined
Oct 22, 2005
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I got my first chance to handle a Sebenza this afternoon. Three actually, a large Regular, a large Classic Micarta, and a small Classic Micarta with partial serrations. The large Regular felt great in my fairly small hands. The large Classic felt a touch long overall, though I can imagine it being just right for someone with large hands. The small Classic was a perfect fit.

One thing I noticed about the three knives is that, when the knives were locked open, the lock bar covered varying percentages of the tang. One covered about 30 percent of the tang, the next 45 percent, and the third 65 percent.

I would think that a higher percentage is better in terms of protecting against lock failure, but I'm not sure what the "ideal" percentage or CRK spec is. I also read somewhere on this site that, on some knives, the percentage of tang coverage will increase somewhat with use/break-in. In other words, if it starts out at about 30 percent, it may go to 50 percent after the knife is broken in.

As much as I loved the knives, I hesitated for this reason. Any input is appreciated.
 
i am assuming you are referring to the lateral coverage preventing the blade from closing. mine covers about 40%. it is about two years old and has been handled a lot. i dont recall if the coverage has increased, but metal on metal will inherently produce wear. although very minimal since it is titanium on s30v.

i would bet if you carried and used a sebenza for the rest of your life you would never experience lock failure. it would take quite extreme conditions to produce this.

and the large classic and large regular have the same overall dimensions. the blades are profiled a little differently and the scales slightly different, but length should be identical between large reg/classic, and small reg/classic.
 
My brand new regular was around 30% now probably 50% but you can always apply pressure with your fingers if you feel that its not enough. I was doing some spine whacks with moderate force that would make dents on wood, and at 30% the knife was solid. But is different story if its at ~10% the blade will actually close on you.
I agree with your if you put both regular and classic side by side the classic is couple mm longer both the blade and handle. I use a regular for EDC. And a classic with wood inlays for weekends :D
 
MORIMOTOM said:
although very minimal since it is titanium on s30v.
Click to expand...

Well, BECAUSE it is titanium vs S30V there is big difference in hardness.
Also Ti is quite soft and scratches easily. So you can experience bigger amount of wear than in steel framelocks.
 
huugh said:
Well, BECAUSE it is titanium vs S30V there is big difference in hardness.
Also Ti is quite soft and scratches easily. So you can experience bigger amount of wear than in steel framelocks.
Click to expand...

Excepted if the lockbar is heat treated, see hereafter an interesting thread on this topic http://www.bladeforums.com/forums/showthread.php?t=441016&highlight=lockbar
and for the lockbar engagement look at this : http://www.bladeforums.com/forums/showthread.php?t=128855

Good reading
 
Two points:

1) CRK inspects all (100%) of the knives (at least based on the info in their DVD) and all knives must be between 50% and 75 % or the knife is rejected. They have gauges that they test this with.

2) As stated above, the lock bar is heat treated and is harder than the blade tang steel. I have this straight from CRK's factory. While they don't RC the TI lock bar (like they do the blade), I was told that the lock bar could reach as much as 90RC...the blade is, if I remember correctly, around 57 - 59.


So, there can be wear over time...but it seems that it will be the tang that wears and not the lock bar.

My small regular Sebenza in relatively new and the lock bar moves in about 60% of the tang...I hope that wear is slow. I suspect it will be...just think about how long you can rub a hard piece of wood against steel (moving it only approximately 2mm) before the wood wears substantially. The s30v blade is harder than the wood and has much larger carbides that will resist wear.

I try to worry about wear, but then I come to my senses and realize it will likely be very slow.
:)
 
Thanks for your input. My assumption initially was that a higher percentage of coverage (e.g., 70-80 percent) was better than lower. But I've learned two things since then. First, Sebenza locks don't fail (even at 20-30 percent) and the percentage of coverage will increase with time and use.

Enough research! I'm ready to purchase my first Sebenza! Thanks to you and Neil Ostroff at True North for input on this question.
 
JohnM said:
Thanks for your input. My assumption initially was that a higher percentage of coverage (e.g., 70-80 percent) was better than lower. But I've learned two things since then. First, Sebenza locks don't fail (even at 20-30 percent) and the percentage of coverage will increase with time and use.

Enough research! I'm ready to purchase my first Sebenza! Thanks to you and Neil Ostroff at True North for input on this question.
Click to expand...

you will love it!! and yes neil is awesome.
 
Garonne said:
Excepted if the lockbar is heat treated, see hereafter an interesting thread on this topic http://www.bladeforums.com/forums/showthread.php?t=441016&highlight=lockbar
and for the lockbar engagement look at this : http://www.bladeforums.com/forums/showthread.php?t=128855

Good reading
Click to expand...

Hmm, interesting.
[urlhttp://www.chrisreeve.com/sebenza.htm]CRK[/url] states use of 6AL4V Titanium for handle.
As you probably know, this grade of Ti has Rc hardness in mid 30s.
(see reference).

Grade 19 (Beta titanium) is heat treatable, but in such case it would be necessary to heat treat whole handle, not just end of lockbar. Then it may get close to Rc 50

Also even Beta Ti isn't capable to reach hardness higher than (cutlery) steel :eek:


So I call this either misinterpreted or plain wrong.
 
huugh,

I'm not a steel expert but I'm pasting the exact email statement from CRK below:

"As for the heat treatment, the lock is harder than the blade and the blade is heat treated to 58-59 RC. We don’t actually test the hardness of the lock, but it could well be 90RC. I would be happy to have Tim phone you if you have any more questions regarding heat treating."

I'm making the assumption that CRK's folks know what they are talking about. At any rate, Sebenza owners, by and large, seem happy.
:)
 
It sounds like the lock bar may be harder than the blade steel. Either way, what are the implications of wear at either or both of these two points? Does anyone have any experience wearing the tang (or bar) to the point that the bar moves farther right and is almost lined up with the blade? How much use does this take? If this happens, is the lock bar then difficult to move back to the left to close the blade/knife? Or is this really a non-issue?!

Please forgive me if the answers to my questions are obvious. I'm new to the Sebenza world and am interested in how these knives wear in practical use.

In closing, what percentage of tang coverage would you like to see in a brand new Sebenza (e.g., 30, 50, 70 percent)? I'm now thinking that lower is better given the overall strength of the lock. Thanks.
 
I will say that my Large Reg. Sebenza locks at about 40-50%, but if I squeeze the handle as in a tight grip, the lock will go in further, although I try not to do that too much. However, doing that hasn't seemed to accelerate any wear when it locks open upon opening. I've had mine since October '02.

IMO, the CRK integral lock is the closest a folder comes to a fixed blade, though I do not do anything to abuse the lock.
Jim
 
plowboy said:
huugh,

I'm not a steel expert but I'm pasting the exact email statement from CRK below:

"As for the heat treatment, the lock is harder than the blade and the blade is heat treated to 58-59 RC. We don’t actually test the hardness of the lock, but it could well be 90RC. I would be happy to have Tim phone you if you have any more questions regarding heat treating."

I'm making the assumption that CRK's folks know what they are talking about. At any rate, Sebenza owners, by and large, seem happy.
:)
Click to expand...

Some coatings get close to 90 HRC, but AFAIK Sebenza's lockbar isn't coated with anything. And hardening 6AL4V grade Ti to 90 HRC isn't possible, not even for CRK :)
(just for reference, it would be around (rough approximate, as this isn't intended for metals) 9 on Mohs scale. Do you get a picture?


BTW you can perform "simple" test: first you can try to scratch glass with the blade (glass is usually around 60HRC). You will see if you succeed. Then you can try to scratch the glass with lockbar. If it is of 90HRC it should be very easy to do so :thumbup:
 
I`ve been working with different Ti allöys in the shop of my favourite knifemaker here in Germany.
Ti 6Al4V has a RC hardness of 25 to 30 and heattreating does not improve hardness more than 2 or 3 points. Beta Ti as used by Mission knives has an average of 35 to 37 RC and is heattreated to achieve this hardness.
If Ti 6Al4V could be heattreated to anywhere over 60RC while keeping its spring properties and flexibility it would easily outperform any currently available bladesteel on the market,which is not the case.
Ti nitride coatings though do offer a hardness of aver RC 80.
So any Ti liner will eventually wear rubbing on a 50+ RC blade.
Owning 5 CRK folders where the lockbars`tangcoverage vary from 30 to 60 percent without any significant change over thre last coupöe of years I have full confidence in the way Chris Reeve designs his line of folders.
 
I think the hardness of the titanium is due to formation of a layer of titanium oxide when the metal is heated and it is just on the surface. It does not change the crystaline structure of the metal in the same way as heat treating steel.
 
Shing, you hit it right on the head. It is a very hard thin layer on the surface. I thought it was in the 70's for some reason.
 
This is an interesting discussion. I can't really address the technical aspects of the TI heat treat and the resulting RC. I can, however, say that the folks at CRK's factory did specifically say that the lock face is harder than the blade tang.

Maybe Shing and proguide are correct and it is only a very thin surface that reaches RCs higher than the tang. I suspect this is sufficient to prevent wear to the lock face. I also suspect that any wear to the tang, assuming this is were the wear will occur, will be extremely slow. I base this assumption on the fact that s30v is suppose to have high wear resistance.

If the frame lock holds up as most of you and CRK suggests, then the Sebenza is, without doubt IMHO, the greatest folder currently being made as a production knife.
:)
 
The lockbar on mine moves over about 25% to 30%. I've found that you can take it apart and when putting it back together, move the stop pin collar and get either more coverage or less coverage. I also discovered that if you tighten the screws with the the blade open AND tighten the pivot first that this can increase the amount of coverage for the lockbar. Why..............not the foggiest!
 
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