Sebenza 21 Edge Deformation, Second Time!

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oXObsidianXo

Joined
Dec 30, 2013
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390
So today I was doing some work outside, and I needed to cut some tar paper. I decided that this would be a good task for my Large 21. I measured the tar paper, placed the area that needed to be cut, on a piece of plywood. I made sure there was no nails or anything in the wood before cutting on it. I cut 3 lengths of tar paper, and went inside. When I got inside, I cleaned the tar residue off my Sebenza, and that when I noticed the edge had deformed at the spot that did the cutting.

I when and gave it a few swipes on the .6 micron ceramic, and then some passes on the .5 micron strop. Here's what it looks like now.

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I wasn't applying any unnecessary force on the blade, nor was I torquing the blade side ways. If you look carefully it's almost as if the apex of the edge has a slight flat spot. This is the second time something like this has happened however. I used to work in a warehouse, and part of my job involved cutting cardboard boxes. After a few weeks of work, I ended up with a Large roll in my blade. So much so, that I had to take the knife to a store to have it re-profiled. The roll ran roughly 3/4" to 1" of the blade, and was located right near the same spot this most recent deformation occurred. The first roll occurred with the factory convex edge, and the second deformation occurred with a 40 Degree inclusive bevel with a 34 Degree micro-bevel.

I am not trying to bash CRK, I love their knives. I just want to know why this is happening to my Sebenza doing what I consider to be light cutting tasks.

Lastly, my Sebenza is a Large 21. Birthday: November 27, 2013. In case anyone else has had similar issues with Sebenzas from this time of production.

EDIT: Upon further examination, I think Unit may have been correct, I think the abrasiveness of the tar paper wore a slight flat spot on the edge. As if I was cutting sand paper.
 
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First off, what you describe is not much of a surprise. Tar paper (as I have experienced) often contains abrasive particles, and this sort of edge deformation is what I might expect after such duties. I'd recommend sharpening it. I'm not trying to be a jerk, knives get dull when you use them.

Second, it's not possible to have a micro bevel that is more acute than the primary edge bevel. Perhaps you mixed up the 34 and 40?

Finally, and this is pure conjecture based on the images you provided but it appears that your bevel widens at the belly and near the tip. This leads me to speculate that your edge bevel may be a bit more acute that you think. If this presumption is correct, I would certainly expect your edge to deform more easily in this area given the duties you describe.

If you are legitimately concerned, call CRK and tell them about it politely. I'm sure they will ask you to send it in, and they will fix it up.
 
oXObsidianXo said:
So today I was doing some work outside, and I needed to cut some tar paper. I decided that this would be a good task for my Large 21. I measured the tar paper, placed the area that needed to be cut, on a piece of plywood. I made sure there was no nails or anything in the wood before cutting on it. I cut 3 lengths of tar paper, and went inside. When I got inside, I cleaned the tar residue off my Sebenza, and that when I noticed the edge had deformed at the spot that did the cutting.

I when and gave it a few swipes on the .6 micron ceramic, and then some passes on the .5 micron strop. Here's what it looks like now.

m1yN4m4Be9jf3YMU


d9f8Rv7pJ3maAddF


I wasn't applying any unnecessary force on the blade, nor was I torquing the blade side ways. If you look carefully it's almost as if the apex of the edge has a slight flat spot. This is the second time something like this has happened however. I used to work in a warehouse, and part of my job involved cutting cardboard boxes. After a few weeks of work, I ended up with a Large roll in my blade. So much so, that I had to take the knife to a store to have it re-profiled. The roll ran roughly 3/4" to 1" of the blade, and was located right near the same spot this most recent deformation occurred. The first roll occurred with the factory convex edge, and the second deformation occurred with a 40 Degree inclusive bevel with a 34 Degree micro-bevel.

I am not trying to bash CRK, I love their knives. I just want to know why this is happening to my Sebenza doing what I consider to be light cutting tasks.

Lastly, my Sebenza is a Large 21. Birthday: November 27, 2013. In case anyone else has had similar issues with Sebenzas from this time of production.
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Wait what? How can you have a micro bevel that is less obtuse than the primary?:confused:
 
Sorry, what I meant was that the bevel was 40 degrees, and I used ceramics and a leather strop at 34 degrees to remove the shoulder. Similar to what a sharpmaker does with its 40/30 sharpening.

@Unit, the bevel is actually thicker at the tip. I didn't want to remove too much material from the blade, so I left the last 1/4" of the blade the way it was from the last sharpening. SEE EDIT at bottom of original post.
 
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I agree with Unit also, it just looks like a worn area from cutting a pretty nasty material. If you use your knife you will get things like this happening, CRK are great knives but they're not magic. :p
 
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Yeah, cardboard is notoriously contaminated with abrasive fines also. In the real world, you rarely cut only what you *think* you are cutting, and in this virtual world we obsess over the conditions of our edges.

You cannot use a knife AND have a pristine edge at all times (stuff happens). I'm GLAD you are using that knife and enjoying it! (For what that is worth to you;))
 
Edges do have the tendency to become dull after being used. :O
The solution is to sharpen your knife or... not use it.
 
Not to be rude, but I didn't ask for a smart ass comment. I originally thought the edge had become deformed. Then Unit informed me that tar paper was quite abrasive, and then I realized what had really caused this. If you had seen the edge before I stropped it, your opinion may have been different. It didn't look dull, it looked flat. And I didn't think cutting 3 pieces of tar paper would have been that abrasive. Add to that, what I mentioned about my edge rolling previously, and your comment has no place here.
 
Thanks Unit for clarifying everything for me.

@buckeyejake, as I said in the original post, the paper was cut on a piece of plywood.
 
I hate to say it but I would never use my Sebenza, somethings are better cut with a razor blade cutter. I cut roofing tile with Spyderco and it took 4 hrs to sharpen it back to shape.
 
sams said:
I hate to say it but I would never use my Sebenza, somethings are better cut with a razor blade cutter. I cut roofing tile with Spyderco and it took 4 hrs to sharpen it back to shape.
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Yup, it's a choice we all have to make.

My rule of thumb is, if it's a spur of the moment cut, I use my knife. If it is a planned work task that generally requires specific ergonomics, and a specialized blade (such as a hooked blade or a thin wharncliffe) I will use the knife a pro would use (generally a retractable utility knife).

Sure the Sebenza or Insingo could do these, but honestly they are not designed for all day use as a carpet removal tool, of a shingle cutter.

Just my modus operandi. YMMV;)
 
Happy to see you use your Sebenza. I should probably plan ahead more but it is usually grab my CRK and cut. One thing about edges they can always be restored. If it means resharpening or stroping is stead of using my CRK I will always go with using my knife. That is the fun in owning a CRK it can always be made to look new.
 
I used to think an edge rolling was a bad thing. I prefer an edge rolling to one chipping.

One of the things that I like about CRK is that they are easily serviced. All of these new super steels are great but I don't want to spend the time to sharpen S90v or 110v.
 
CPM S35VN Stainless Steel - currently it is in the Super Steel category. Unless it is changed when I was napping.

My other folders using CPM S35VN, S90v, 110v, ZDP 189 and .....having different scale HRCs, hold their edge well.

On the other hand, just feeling edge sharpness, prompt me to make a light touch up with the Sharp Maker UlterFine. My Insingo will rarely need to face my WEP, until it is for an inevitable conservative reprofile, resulted from all the frequent light touch ups. :)
 
I used to get this exact same deformation with my Sebs, the edge would just flatten or dent inward. No rolling or chipping, just denting or flattening it was weird. Never seen that deformation on any knife I've used in my lifetime. Got my sebs hardened and haven't seen the issue since. Would be cool if CRK ran some Sebs harder for those that prefer the higher HT.
 
TTTis said:
I used to get this exact same deformation with my Sebs, the edge would just flatten or dent inward. No rolling or chipping, just denting or flattening it was weird. Never seen that deformation on any knife I've used in my lifetime. Got my sebs hardened and haven't seen the issue since. Would be cool if CRK ran some Sebs harder for those that prefer the higher HT.
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What do you mean you "got your sebs hardened"? Did you send them to another maker to have your blade re-heat treated? Doesn't that mess with the tolerances?

As for the people saying they would normally use a specialized blade for the task I performed. The reason I used my sebby was because the last time it did some serious cutting the edge rolled on me. I had wanted to put it through its paces again to test the edge retention/stability since it had been re sharpened, normally I would have used a utility knife as well.
 
That's great and I'm not saying I wouldn't have perhaps done the same. Small jobs?...use what ya got. Big jobs will show you why a really thin blade (that might break and get replaced several times throughout the job because it's faster and easier than sharpening the last one) on a big ergonomic handle (that won't cary nicely in your pocket) is a better choice sometimes.

It's all good, but poor results with a Sebenza does not necessarily indicate a poor example of the knife...the fault could be the suitability of the job to the knife's design.
 
unit said:
That's great and I'm not saying I wouldn't have perhaps done the same. Small jobs?...use what ya got. Big jobs will show you why a really thin blade (that might break and get replaced several times throughout the job because it's faster and easier than sharpening the last one) on a big ergonomic handle (that won't cary nicely in your pocket) is a better choice sometimes.

It's all good, but poor results with a Sebenza does not necessarily indicate a poor example of the knife...the fault could be the suitability of the job to the knife's design.
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Ya, I realize now that I may have chosen a poor task to use my sebby for. But none the less, I enjoyed using it, and the actual damage to the edge is nothing I can't take out. This made me realize I need a wharncliff style blade for these types of tasks :)
 
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