Lowest practical inclusive angle for edges on various steels?

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gomipile

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We've seen a lot of comparison of various blade steels' edge retention at different Rc values. Well, some steels are able to remain tough enough to use for normal tasks at higher Rc hardnesses, such as ZDP-189, Elmax, S90V, etc.

What I'd like to see is a list of steel+hardness listed in order of edge angle, where all of the (steel,angle) pairs have roughly equivalent edge durability(resistance to chipping/rolling, not edge retention.)

I don't know if anyone can really answer this, but it's something I've been thinking about for a while, and maybe someone will come up with something like this in the next few months.
 
Ankerson said:
Too many variables to make a list like that.
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As simply as I stated it, you are right. I'm sure that one could come up with a reasonably scientific way to define a set of tests to get it reasonably precise though. As precise as things like Rc values anyway, which aren't very precise anyway.

However, what I'd really like is an imprecise "real world" list. Just a list of the lowest angles that are really practical for a given type of task. Say, a list for cutting nothing tougher than 3 ply corrugated cardboard, and another list for cutting nothing tougher than sushi.
 
gomipile said:
However, what I'd really like is an imprecise "real world" list. Just a list of the lowest angles that are really practical for a given type of task. Say, a list for cutting nothing tougher than 3 ply corrugated cardboard, and another list for cutting nothing tougher than sushi.
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Besides alloy, hardness, geometry, it also depends on the user's skill. I can tell form my own experience, as I got more experienced with knives, I was able to grind lower and lower angles w/o damaging them during the same use. So, the angles will be very approximate, or wide ranges, but that isn't really that much valuable, because the difference in cutting performance between 15 per side and 10 per side is really huge.
E.g. I can say for Aogami 1 at 65 hrc, 270mm long gyuto, 5 per side works just about perfect for me. On the other hand, 90% of the folks easily deform twice as thick edge, or even thicker... Another example, I got Aritsugu chef's knife, Gokinko steel, ~61hrc, for now the lowest I can do is 15 deg edge(inclusive, it's a single grind knife), but I know couple other guys who use the same knife a lot more than I do, with the edge between 8-10, they're fine... And all that with quite well defined use - soft food.
Now, imagine something as vague as "field use" or hunting or combat use.
 
i think you just have to settle for generalizations. harder tougher steels can go to lower edge angles than softer alloys generally speaking. ive found some blade grinds are hard to do a real low angle due to the width of the blade above the edge and the fact the stones will hit well above the edge to be practical to do. talking practicalities the actual need to go with a super low angle edge is imo overrated as no matter how sharp it is and what ever steel is used the edge will wear and chip out faster than with a more moderate angle. best bet imo is to find an angle that your happy with for a particular knife and stick with it, unless you just like grinding out expensive blades down to dust. lol
 
The practical angle for any blade steel is likely much more acute than you may believe. I have an Ontario economy machete. 1095 steel, about .080" thick, came with a wide, slightly hollow grind single bevel of 10 degrees inclusive. For a machete! And it works. I've come to the conclusion that factory edge bevels are almost always too thick and obtuse to allow a knife to be as good as it can be.

That being said, there is no hard number that can apply to any particular steel. So much depends on the intended application, hardness, tempering, actual use, and so on. Actual double edged razor blades are usually cheap stainless about .004" thick. They simply don't fail in any way that we'd associate failure with, say, a pocket knife. Obviously, a knife used to pry stuff apart would benefit from thicker, less acute grinds than razor blades.
 
Factory edges very often come well above 20 per side. And usually that's the lowest common denominator, since they(factories) have to deal with abusive users, warranty, etc...
 
gomipile said:
As simply as I stated it, you are right. I'm sure that one could come up with a reasonably scientific way to define a set of tests to get it reasonably precise though. As precise as things like Rc values anyway, which aren't very precise anyway.

However, what I'd really like is an imprecise "real world" list. Just a list of the lowest angles that are really practical for a given type of task. Say, a list for cutting nothing tougher than 3 ply corrugated cardboard, and another list for cutting nothing tougher than sushi.
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Too many variables, way too many...

All of it would depend on the knife, the steel, how it's HT and tempered and the user and all those variables that go a long with it and a ton of others.

The best thing you can do is go to a good Custom maker and talk to them and have a knife made based on what you want and what they recommend.

Other than that..... well.... It's a crap shoot....
 
gomipile said:
Just a list of the lowest angles that are really practical for a given type of task. Say, a list for cutting nothing tougher than 3 ply corrugated cardboard
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Cardboard can be some of toughest edge killing stuff there is depending on the cardboard being cut, it can and does vary a lot from really easy cut all day to extremely tough tearing up edges in a few cuts.

I have killed a lot of edges on more knives than I can remember over the past 25+ years cutting cardboard, that's both at work and in testing.

And it doesn't have to really thick either to do the damage.

And that's not even getting into all the other variables...
 
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I sharpen on a slack belt at a 10 degree angle and it works out fine due to the slack belt always creating a mild convex of sorts. With a clean v grind secondary angle it would not be as advisable.

;)
 
I have tried a lot of angles and a lot of steels. I have a folder at home ground at 7 degrees inclusive, and I arrived at 7 after several intermediate steps (20, 15, 13, and finally 7). As much fun as it is to play with bevel angles, I have come to find that a 30 degree inclusive is common for a reason.

The thickness of the edge behind that bevel....now there is a place to find performance!
 
unit said:
... I have come to find that a 30 degree inclusive is common for a reason.

The thickness of the edge behind that bevel....now there is a place to find performance!
Click to expand...


That's where my head is at, too. Any good steel should be able to hold a 15/15 edge for EDC purposes. If it can't, I'd switch to a steel that can.

I have issues with some design elements of the Gayle Bradley, but one thing about that knife that is just about perfect is the blade. M4 steel is tough and holds a good edge. So the designer took advantage of that and designed a blade with a thin, hollow grind and an edge with a thin shoulder width. Spyderco's heat treat, which I think is about 62 HRc, is close to perfect, too.

Benchmade's huge Onslaught comes in 154 cm. It came extremely sharp from the factory with an even, 15/15 edge. It's a flat grind on a wide edge, with the swedge sharply tapered. Its edge shoulder is even thinner than the Gayle Bradley. I don't know what the hardness is, but 154 cm steel is no stranger to Benchmade.

My Sebenza is S30V that is soft, maybe 57 HRc, if I remember correctly, but that's not too bad for a more brittle steel like S30V, especially with a convex edge. It picks up slicing ability with a very thin edge shoulder.

So, as has been mentioned, there are lots of variables, but I use the same 15/15 edge on all these quite different knives. For me any good steel will hold a 15/15 edge. If I need more slicing performance, I can go to a thinner grind. But the 15/15 is nice because it's the lowest edge my Wicked Edge will sharpen to, and it works perfectly with the Sharpmaker, which I use for quick tune-ups between major sharpenings.

In addition, I strop between sharpenings manually on a strip of leather glued to a block of wood. Stropping requires the correct angle. If I use the same 15/15 edge on all my knives, my muscle memory makes things easy. Too many different angles becomes a nightmare to keep track of.
 
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