optimum bevel for sebenza

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possumman

Joined
Feb 28, 2007
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i've got a sebenza s30v which is an outstanding knife. it appears to have come with a 40 degree inclusive bevel. would it be wise to thin it out to 30degrees or not? possumman
 
When I sharpen my Seb for the first time I am going to stick with the 40° (20° per side) that CRK suggests. If 40° inclusive looks good I might try 30° the next time. I have three pocket knives with thin blades that I ground to 30° and the side of the edge is rather wide.
 
If you want better sharpness and edge retention thin it out to 30 inclusive or less. I run my Manix at 10 per side with a 15 degree microbevel with no durability issues, unless you hit metal. You are leaving a lot of cutting ability, sharpness and ease of sharpening in the bag if you leave your knife at 40 inclusive.

Mike
 
For my large classic, anything under 10 degrees per side began to engage the top of the tip and the cut bevel.

If stock looks are important, this is a consideration.

MAT
 
i guess part of me wants to maintain stock looks. i'm not sure i want to go to shallow a bevel but maybe 30 degrees (inclusive) would be a good compromise?
 
Steven Andrews said:
I don't understand how a shallower angle can increase edge retention .. :confused:
Click to expand...

Read up on it, and check out some of Cliff Stamp's testing. Joe Talmadge I belive also talks about this, so check out the steel FAQ at the top of the page. Another good example that Cliff stamp used to show the difference an angle makes is using Buck's CATRA results when they went from a more obtuse convex edge to a more acute flat edge. Then, 420 HC was outlasting BG-42 in edge retention. See here: http://www.bladeforums.com/forums/showthread.php?t=421313

It kind of opens your eyes to see a "super steel" outperformed by a "junk" steel just because of superior edge geometry.

My own experiences have shown me that I get better sharpness, ease of sharpening, and edge retention by going thinner and more acute.

Mike
 
Thanks for the link.. I'm still not convinced though. I can see that whether an edge is convex or flat effects edge retention - but not the angle of that edge.

Two blades - identical steel, identical edge grinds, identical "sharpness". A shallower angle will stay sharper for longer? I don't see it.

Yes, shallower angle are easier to get sharp and easier to sharpen when they get dull, but in my experience they don't stay sharper for longer.
 
I don't believe there's an optimum edge angle for a Sebenza, or any other knife per se - it depends on the type of work to be done and materials being cut, as well as the steel and heat treatment, and other qualities of the knife itself.

Under some conditions reducing edge angle will result in lower edge retention, e.g. too acute for the properties and inherent edge stability of the steel. But this also depends on the kind of edge you choose to run (coarseness or fineness of finish) and the type of cutting involved.

Now that the issue is sufficiently confused :) ... my "default standard" is to sharpen nearly all knives that are going to see general utility use to about 12 degrees per side primary angle, and apply a microbevel of about 17 deg/side. You may be more skillful with a knife than I am, or cut mostly lighter materials, or even have found a blade from some maker or mfgr. that allows you to run your primary edge more acute. However I kind of doubt with an S30V Sebenza that that would work out.

If it turns out that 12 deg/side is too acute - and it might with a high carbide alloy like this - it's very easy to apply a light secondary bevel of say 15 deg/side, then microbevel at 20 deg/side (the work reprofiling to 12 deg. really wasn't wasted, because now it's much easier to add a secondary bevel.) If the edge doesn't hold up to most use at those angles, something is probably wrong with the blade.
 
I sent a small Classic Sebenza back to CRK to have the edge thinned out. The knife was sharp but because of the thickness of the edge it was not as good a cutter as it could be. I think thin will always out cut thick blades and that is what I want on a knife. Also, I use a knife to cut with and not pry with and I have older Sebenzas with thinner edges that have performed great.Oh, by the way I have broken blades on knives in my younger days by prying or doing things with a knife that I know now was abuse.
RKH
 
Both Reeve and Strider folders come with edge bevels of 40 degrees or greater included, which I assume is intended to enforce their reputation for offering tough blades. Some portions of the edge of my Strider SMF approached 50 degrees included.

Most of my folders are S30V, VG10, D2, BG42 and ATS34. Primary applications are slicing (no impacts) of materials up to hardwoods.

Since the hardest material I intend to cut are hardwoods, I experimented a bit with edge profiles. Tests consisted of multiple pointings of a hardwood rake handle.

All blades chipped to some degree under hard-pressure locked-wrist pointings with final edge bevels less than 30 degrees included.

All of my folders perform very well with main bevels of 10 degrees and edge micro-bevels of 15 degrees per bevel.
 
As someone said earlier if you thin the edge to 10 -12 degrees it will definitely alter the look of the blade, but boy will it cut!
 
Are you wanting to use a Sharpmaker or another fixed angle system? IF not. You could always just convex the edge and you can easily ajust the thickness or thinness of your edge. They are by far my favorite type of edge, easy to maintain, and look great. They are also just as sharp and strong as any other edges. Truthfully the angle that is best for you depends alot on what and how you use your knife. As you can see 10 degrees can work for one person and 15 works best for another. Same goes for coarse vs polished edges. :) With that said convex edges rule. :)
 
Steven Andrews said:
Thanks for the link.. I'm still not convinced though. I can see that whether an edge is convex or flat effects edge retention - but not the angle of that edge.

Two blades - identical steel, identical edge grinds, identical "sharpness". A shallower angle will stay sharper for longer? I don't see it.

Yes, shallower angle are easier to get sharp and easier to sharpen when they get dull, but in my experience they don't stay sharper for longer.
Click to expand...

The very edge is all that is doing the cutting, so the convex vs. flat doesn't hold water when you are talking just the edge angle. The convex vs. flat will affect cutting ability depending on the cross section behind the very edge, but the steel at the very edge is all that is doing the cutting, and those CATRA results speak for themselves, as the 420 HC at a more acute angle had better edge reteention than BG-42 at a more obtuse angle. Also check out this link: http://www.bladeforums.com/forums/showthread.php?t=420917

Notice the angle on the Fallkniven U2 is 4 degrees per side with a 15 degree microbevel, and it out performs ZDP 189 at 8 degrees per side with a 15 degree microbevel significantly in edge retention. At those angles you have to be careful about proper technique and definately have a more limited scope of work than a more obtuse edge, but a knife with a supposedly much lower wear resistance beat the ZDP-189 knife in slicing edge retention, possibly due to the thinner angle. I have both knives in my possession now, and have had the ZDP 189 knife reground so it can be brought down to the 4-5 per side range and I plan to re test them to see if the results change. If you do more research you will find that it just isn't true that thicker angles mean better edge retention. Like was said previously, things like the steels ability to hold a thin angle without crumbling, what you are cutting, how you are cutting it, ect., all play a major role, but many tests have shown that thinner edges generally have better edge retention, assuming the steel won't roll or chip at the thinner angle. I think it would be safe to say you can go to 15 per side on a Sebenza without affecting the looks significantly, but you will notice a nice gain in edge retention and sharpness if the steel is properly heat treated.
 
gunmike1 said:
The very edge is all that is doing the cutting, so the convex vs. flat doesn't hold water when you are talking just the edge angle.
The convex vs. flat will affect cutting ability depending on the cross section behind the very edge, but the steel at the very edge is all that is doing
the cutting,
.. .
Notice the angle on the Fallkniven U2 is 4 degrees per side with a 15 degree microbevel, and it out performs ZDP 189 at 8 degrees per side with a 15 degree
microbevel significantly in edge retention. At those angles you have to be careful about proper technique and definately have a more limited scope of
work than a more obtuse edge, but a knife with a supposedly much lower wear resistance beat the ZDP-189 knife in slicing edge retention, possibly due to
the thinner angle.
Click to expand...
I know I’m on his ignore list but I’m confused. 15 degrees and 15 degrees are the same edge angle. Also, sure if you have no edge damage neither the thin or thick edge dulls, and yeah thinner cuts better. However, in real life finding the balance between sharpness and edge damage greatly relies on what type of work and how you use your knife. So to say thinner edges last longer just isn’t so. You could sharpen like HoB does and go thinner and thinner slowly each time you sharpen until you are happy with what you have or see damage. You don’t need to jump down to 10 degrees all at once.
 
Thinner edges don't 'last' longer, but for a given measure of force, lower edge grinds can/will continue to cut longer than more obtuse ones. Go to an extreme-a zero degree edge, no bevel applied. So, you've got your 1/8" piece of steel, and you have X amount of cutting ability (X is pretty crappy, given) Now, you cut a bunch of cardboard, split some hairs, slice newsprint, peel potatoes, whatever you can manage with a 1/8" edge. With whatever wear you have experienced through all this work, how has the edge thickness changed? And through the change in thickness, you have a change in cutting ability. But the thickness hasn't changed, because it is constant throughout the cross section of the 'knife' due to the zero degree bevel. Sure, 1/8" isn't going to cut anything, but what if it were 1/8 of a micron-wow, that's sharp, and it stays that sharp.

But, what about deformation of such a fine edge? Well, if I have a ball of play-doh the size of a marble, and another the size of a baseball-and I throw both against the wall-which one is going to make a larger diameter flattened disc? Similar with denting of edges, if you start with thinner metal, you end up with thinner flat spots.
 
When dealing with a fairly benign dulling, such as cardboard, thinner edges have better edge retention. This is barring impacts/cutting wire/chopping concrete/etc. where thicker edges have better edge retention.

Does this pretty much some it up?
 
FlyingMuskrat said:
When dealing with a fairly benign dulling, such as cardboard, thinner edges have better edge retention. This is barring impacts/cutting wire/chopping concrete/etc. where thicker edges have better edge retention.

Does this pretty much some it up?
Click to expand...


Pretty much, IMO. The really thin knives I've used are capable of much higher sharpness and edge retention with the same 15 degree microbevel I use on my thicker more obtuse knives, I don't know whether it's the thin edge, acute primary with barely there microbevel, or a combination of those that lead to the much better sharpness and edge retention on cardboard. For instance, on that U2, I can cut straight into the stone to completely dull it, and 5 strokes per side on Spyderco medium stones at 15 per side and it is tree topping hairs with ease. My flat to the stone Jess Horn (not Krein reground) can't get that sharp, but gets much sharper than it did with the factory edge angle. I have to bring my thicker knives up to the Spyderco Ultra Fine (using more strokes per stone) to approach (but not even equal) that level of sharpness at a much coarser finish on the U2, and lose a lot of the slicing aggression in the process. For whatever reason the ultrathin knives just get sharper and seem to hold it better on cardboard and other things like plastic packaging, food, ect. For me, the thinner and more acute, the sharper I can get it, still using my 15 degree microbevels. They aren't for everyone, though, as you do need to cut fairly straight with them (no heavy twisting cuts) to avoid chipping, and you definately don't want to hit metal with them. They aren't a do it all, take on any job type of knife, but I carry heavier duty knives along with the thin ones for different cutting situations.

That being said, I could see someone not wanting to mar the finish of their Sebenza, and wanting to have it be able to handle heavier duty work. At 15 per side with a 20 degree microbevel, as Sal Glesser recommends in his Sharpmaker video, the Sebbie would cut much better and still be very durable compared to a straight 20 degree per side edge. If that combination proved durable, you could always go thinner gradually until it takes damage (as Murray Carter suggests in his video) and then back off. You would then be getting the maximum performance for your uses. It all depends on what and how you are cutting. Or, you could just leave it as is if you are happy with the cutting ability at the current angle. It just so happens that for me 10/15 works well for my heavier uses (thicker plastics, heavy cuts on wood, ect.), but I would most likely suffer a decent chip if I hit a thick staple in a box I was breaking down. I am willing to live with that for the increased cutting ability for the other 99% of cutting I do, and I keep my eyes out for packing staples when I break down cardboard. Either way do what you want, it is your knife (and a nice one), enjoy it, and do what you feel is right for you.

Mike
 
Also, the thinner edge will start cutting LONG before a thicker edge, so at a given force, you're already well into the cut, as opposed to just getting started with a thicker one. Even when dullish, the thin edge has a better geometry than a thicker one (in general).

Here's what a Sebenza looks like when thinned out, I'm trying to remember how thin, not quite as thin a bbcmat's. His is a work of art, no kidding. Sorry for the other knives, I was inventorying my collection and have different ones in every shot.

http://i137.photobucket.com/albums/q203/sodak_photos/p1010005.jpg
 
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