Chisel Edge Blades

[SIFU1A]

today i accomplished, w/many hours work, what was imho impossible - to get a chisel edge hair poppin razor sharp - well w/the assistance of a spyderco ceramic stone, a good strop and steel,and a lot of time my BM975SBT is now hair poppin sharp!!!!!!!w/my old emerson CQC7 ya could only get it so sharp, but w/the BM ya can, eventually, get a good edge - even though it is a left hand grind, lol - i swear ya could hone on that emerson till gabriel blows his horn and it wouldnt shave........and i thought it was ME11111


sifu

 

[RJ Martin]

Gents: Well, there are some interesting statements here, but, I have to say that some of them seem like they are oversimplifying the issue.
Comparing chisel grinds to double grinds is very difficult, and, without actually measuring the thickness of each, say, .06 behind the cutting edge, you are likely to get inconclusive data. Generally, double ground knives will have substantially more material behind the cutting edge, particularly if there is an edge bevel.
Cliff-your statement that a chisel ground knife's cutting ability depends solely on the grind angle is surprising. What about heat treatment? Also, how do you consider rotating the handle approximately 9 degrees to orient a chisel ground edge symmetrically something that is going to put your hand in an uncomfortable position. Try it-you'll barely be able to feel the difference.
Hollow chisel grinding a knife produces a knife that is certainly WEAKER than a straight chisel grind, because the cross section behind the edge is less. Besides, it's totally non traditional, and is absolutely the fastest way to grind a blade of this type.
Anyway, as I said, the discussion over chisel ground knives is largely based on personal preference. I've made hundreds, if not more than a thousand of them, and, have never received one back because it didn't hold up in service. No, they are not indestructible-you can ding them and chip them if you cut materials like bone. This is why meat cleavers have a convex grind.

Just thought I'd stir the pot...

 

[Cliff Stamp]

R.J. :

Generally, double ground knives will have substantially more material behind the cutting edge, particularly if there is an edge bevel.

Yes, but that is not necessary. For example most hollow ground production knives cut very poorly. This has nothing to do with the inherent abilities of a hollow grind, but simply because it is common to put sallow sabre hollow grinds on production knives. It is the same thing with chisel vs dual flat. The difference in cutting ability (gross blade strength etc.) is due to the choice of knifemaker in the blade stock and grind height. If both are done full height on the same stock thickness and width the resulting edge profile is identical in cross section, just aligned differently.

Cliff-your statement that a chisel ground knife's cutting ability depends solely on the grind angle is surprising. What about heat treatment?

I have never found heat treatement nor steel for that part to play a significant role in the cutting ability of a blade. What steel choice and heat treatment control are aspects like edge retention, edge durability etc. . Now you could bring up the argument that these aspects are all integral parts of a whole design and cannot be considered independently. For example a more durable steel allows a thinner edge and thus a higher performance cutting tool. However the fact remains that the cutting ability is reduced because the geometry is changed.

I know that you have stated in the past that you have found that you can get certain steels sharper than others, specifically you mentioned that you could not get CPM-3V to take the edge that you were able to obtain with A2. Now if this is the case, then the steel and heat treatment will effect the cutting ability as it is strongly dependent on the sharpness. However personally it is not something that I have ever seen. But then again I don't claim to have your level of skill in sharpening.

The only real difference I have seen is that when you take steels to a really high polish so that the cutting edge irregularities are determined by the inherent characteristics of the steel (grain size, carbide formation), rather than being products of the abrasive size (micro-teeth), there will often be a difference in the slicing ability as some steels are more agressive. However this can easily be compensated for by leaving the other steel at a slightly lower finish.

Also, how do you consider rotating the handle approximately 9 degrees to orient a chisel ground edge symmetrically something that is going to put your hand in an uncomfortable position.

There are two basic methods, the first would be to rotate the knife in your hand. This puts the handle in an odd position assuming it is not circular in corss section. If it was comfortable when properly aligned it won't be when rotated. The second would be to rotate your wrist, this lowers the amount of force that can be applied to the blade as thus reduces the cutting ability. And yes, I have done both.

Hollow chisel grinding a knife produces a knife that is certainly WEAKER than a straight chisel grind

Well yes, but the type of chisel grinds we were talking about (very high and acute grinds) are blades that are easily damaged anyway.

-Cliff

 

[Burke]

I'm not sure if this is what you're referring to, RJ, but do you mean rotating the relationship between the handle and the blade, by putting, say, a 9 degree twist in between handle and blade? Or simply holding the knife at an angle to cut?