.....

Go with the majority use, if it's primary function is for defence, go double edge.

If the primary function is utility go with the single edge.

If you have to have both, get one with a swedge.
 
I would favor the single-edge, since some localities have made double-edged knives illegal. Yes, I know it's stupid -- are they trying to say that double-edge knives are sooo much more lethal that they have to be banned? -- but that's the fact of the matter. Does a double edge mean so much to you that if you were to have to use the knife defensively, you would not mind answering charges for having done so with an illegal-to-possess knife? You may say that you are glad to simply be alive after fending off the attack, but then what? The difference between freedom and jail may hinge on whether you opted for a single- or double-edged blade.

I don't know if this has any basis in fact or physics, but it seems to me that a single-edged blade will be stronger than a similar double-edged one since it has a nice sturdy spine. Less wafer-y than a double-edged knife. I had a Tekna Boot Knife that was double-edged. It had to be so thick in the center, for strength, that the result was such a high grind angle as to be virtually crap for cutting. You just couldn't put an edge on the thing that would cut worth anything. Seemed like it must've had a 50-60 degree total angle! On the other hand, you can have a really thick spine on a single-edged knife and still manage to get a slender edge that will cut like crazy.
 
Let me start with a disclaimer: Any weapon is useful. A piece of hard material with a sharp edge can be dangerous. Plenty of people have been injured or even killed with nothing more than kitchen knives, broken bottles or a pointed stick. Any statements I make below pertain to optimal tool design for a task. The added advantages of a certain blade geometry may not add up to much in the grand scheme of things.

That having been said, I believe that the optimal knife for fighting/self-defence is double edged. For fighting, knives have to be able to stab, slice and (if large enough) chop. Long standing common knowledge is that the point on a double edged blade penetrates much easier than a single edge because it is thinner. Double edges also allow you to cut with both the inside and outside of the knife without indexing the blade, which I have found handy especially in reverse grip. The sharp second edge also makes it more difficult to disarm you by manipulating the knife itself (i.e. disarm techniques that put pressure on the unsharpened edge).

The double edged blade is not as good for utility. The thinner tip is more fragile. As has been said earlier, you cannot put finger pressure on the back of the blade if it is double edged (well maybe you could, but it would be messy:p ). Also, you cannot use as shallow an angle for the bevels if they have to meet at the center of the blade, so a sturdy double edged blade is not as good for deep cuts.

If I personally had to choose one knife to do both self defence and heavy duty utility, I would pick a single edged drop point or clip point blade design. I base this decision on the idea that the blade would see more duty as a utility knife than as a defensive knife (hopefully). The drop or clip would still give enough of a point for stabbing if needed but would not be as fragile as a double edged point for it's main intended function. A penetrator tip like the one used on Busse/Swamprat knives might also be a good compromise.

The most important aspect of weapons self defense is mentality. It don't matter what kind of self defense tool you use if you do not have the resolve to use it.
 
Greg Walker, in his Battle Blades book, recommends a combat bowie!

But if you don't want something liek that, he recommends something with a sharpened false edge. Look at the Camillus CQB fixed blades- you have a single edge and a long swedge that could be sharpened with a bit of work. Something like that with the swedge not going so far back would leave a lot of spine area for pounding on, while letting you sharpen plenty of both sides of the tip for easy penetration.

I think for the $65 1sks is charging for the Camillus CUDA CQB-3, you really can't go wrong.

Good luck finding a Kathaku, they look awesome!
 
If you study defensive tactics with a knife in reverse grip you might want to try a blade that has the false edge sharpened only a third of the way from the tip. When (not if) the blade gets pushed up against your forearm when you meet any kind of resistance on a forward cut your arm will get "bitten" by a fully sharpened top edge. This way you can still get some of the benefits of a double edge while keeping yourself a little less sliced up. (No sense doing the job for your opponent.;) )

BTW I agree, the Camillus CQB is a fantastic knife for the price.

-Arnold
 
The main advantage for me of my double edged keychain knife is that it's easier to get into the sheath. The knife is straight and symetrical, so when I had it in a single edged model, figuring out which way it goes in was a hassle.
 
I was wondering also what type of guard is preferred on a fixed blade? Single, double or no guard at all?
 
There are a LOT of disadvantages to the double-edge knife. Especially for utility use. Never underestimate the ability to beat on the spine of a knife to drive it through material (like splitting a log or something) or to apply pressure to the spine for stronger cutting.

Also, single-edge knives generally have better cutting geometry. A DE knife has to be thicker - say if a knife is 2" wide the spine has to taper down to the edge within only an inch on either side, while a nice single edge knife can be flat ground for the entire 2" and have a nice flat profile without NEAR the friction or binding of the steep angle common in DE knives.

DE knives are harder to sharpen. Consider some of the great clamp sharpeners like Gatco, Lansky and another one that I can't remember that's supposed to be REALLY good - they wouldn't work at all on a DE knife. You'd have to sharpen it on a stone with no angle guide unless you used a pole system like the Spyderco Sharpmaker. Just something to think about.

Generally, in my opinion, I think all double-edge knives are a compromise. I think I would ALWAYS lean toward a properly designed single-edge than sacrifice some good design principals and geometry to get two edges.

Hey, how many custom knife makers are making double-edge knives? Not many. I would always trust a good knife maker to make a single edge very well and leave it at that.
 
a compelling reason why not to put your knife on the end of a stick to make a spear. If the pole breaks you have just lost your knife. But a good hard wood, when sharpened and fire hardened is almost as dealy, plus you still have your knife on you if it breaks. But if you really want a knife/spear blade have you looked at the Cold Steel Bushman? It's said to be pretty tough and it's fairly cheap in case you lose it. Just food for thought.

Frank
 
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