Erik :
How efficient is the 50 degree BM edge?
Much more than you seem to imply. Changing the edge angle won't change the chopping performance even close to linear because as noted in the above the performance depends on many other characteristics even beyond geometry such as mass and balance. So when you reduce the edge angle, you are altering just one small part of performance, the total effect thus induced will be much reduced over just the edge angle ratio. I have for example taken knives to belt sanders and cut the edge angles down to half as well as radically increased the shoulder, effectively reducing the edge thickness, and seen a chopping performance of ~50%. Large indeed, but this is at the extreme range where the knives are no longer durable enough for the harder wood working. Bevels which are slimmer than perferred by the people you are referencing.
Lets say for example you changed the edge angle from 25 to 15. This would put the edge on a large bowie at the same angle as on the best of the folding knives you mention (Buck and Spyderco), this is a rather extreme change obviously. The cutting performance for most push cutting would scale as the angle, so you would get about a 75% gain, huge indeed (it depends exactly on how you are looking at it but somewhere in that class). However for chopping it would be far less, in the realm of about half of that. It depends on the penetration depth, so the wood type and user characteristics. If the wood is very soft the gain will be less, if it is very hard it will be more and the more skilled and stronger the user the more of a gain they will see, but in any case far less than for whittling or anything similar. So we are talking about a ~35% change (as an extreme remember), this is hardly enough to change you from being an efficient cutter to "beating" the wood apart. If you went down to around 18-19 degrees, the changes would be close to 40 and 20% respectively. Significant - of course, however not nearly the extreme you are describing which you have described with terms like "useless".
[golok]
... if you bent it, you were using it wrong
The back of the first one I used wasn't spring tempered, it is pretty much annealed hardness. I would agree if it was spring hardened (45+ RC), you would not be likely bend it on any wood working.
I was limbing dead hemlocks, a far more stressful task, and the edge had no damage.
The edge on mine was also very soft towards the tip and took damage readily during any limbing, even on fresh soft woods, it even got visible rolled on just dead stalky weeds. In the middle of the blade where it was much harder, the damage during limbing was only induced during work I would normally not do, sweeping dead limbs, and even then it was light denting. However there is harder woodworking possible such as frozen knotty wood and of course I don't think I am the most unskilled wood worker around, thus user durability requirements can be much higher (and of course lower for the same reason in the opposite direction). I have to repeat this cutting with the other one I have to see if the hardness is consistent, however based on my conversation with the manufacturer mine was the norm. They will also get hardness tested as I am curious just how hard the edge is where it was the most durable.
Try filleting a fish with a 50 degree edge on a 1/4" thick knife, you are not gonna have fillets, you are gonna have mush. You libve in NF, lots of fishermen there, go down to the wharf, show them a NIB BM, and see the
response.
Most of the "fillet" knives used here are actually ground down chef's knives from 20+ years of heavy steeling, a half an inch wide or less. You have usually a blade of 1/8" to 3/16" stock, which is basically just that thick behind the edge (and thus far beyond the Busse blades), and the edge is actually quite obtuse as well. Fish, like most meats is very easy to cut, and induces little binding on a blade as it is easily compressed (compared to something like wood for example). As long as the edge is very sharp it will cut it well. Yes I have done it. The BM doesn't make a great fillet knife though because it is far heavier than needed, but you can get around that with use of the index finger cutout, but mainly because it isn't flexible, and is too wide so turning it is a problem, which is also why it doesn't make a great potato peeler.
... you change the edge grind angle and finish and can get many to one increases in performance.
In slicing performance, you can get a many to one increase by just changing the edge finish alone. This is just a few seconds work, add a micro-bevel along the edge at the finish you want. However, this doesn't carry over into push cutting, and the rougher finish will in fact degrade it many times to one.
Rob Simonich :
... a while back it seems to me you stated that blade materials have very little effect on cutting ability
With equal geometries yes. There are small effects but you need extreme geometries to see them as basically you have to see the effect of the grain size, or have very high standards for sharpness, far beyond normal "shaving sharpness". Not this isn't the entire perspective of course, the material used defines the functional cutting ability as it is dependent on the inherent durablity of the steel.
Eric :
[22 degree edges on folders]
Which companies did you mean
Benchmade was what I was thinking on, if they have altered the profile to ~15 degrees per side that is good to hear indeed. However the 22 degrees thing is common. It is pretty much the most recommend sharpening angle, JJ for example of razors edge, and most sharpening information that comes with knives says it as well, basically cut a 90 in half twice is the common directive. V-rod sharpeners for example, which are commonly used on light knives are most often set to 22 degrees. Note for the companies you mention which are at the extreme (Buck and Spyderco), you are comparing a light use folder to a 10" utility bowie. It is hardly the case that you would expect both to have similar edge profiles. If you would describe the BM as being so unusable, the folders would be even more so.
You give a number for edge angles, which is rather meaningless unless you look at the thickness of the metal directly behind the edge, and this is determined by the primary grind of the knife.
The edge angle alone isn't meaningless and for some cutting it is in fact the dominant factor over the edge thickness, it basically depends on how constrictive the material is on the blade. For some materials this isn't anything at all, whittling hard plastic for example. But yes, getting more specific about the edge geometry gives more information. However is you look at edge thickness, the difference between the BM and a highly optomized wood cutter would be even smaller than the change in edge angle. And the effect of changing the edge thickness is actually much smaller than changing the edge angle, as the constrictive force falls off much beyond linear in height. And this is for light cutting, for chopping it is even less again for reasons stated in the above.
Next, you make these assertions about what it takes to stand up to bone contacts, look at the work that has been done with Hossom knives.
Such of his knives have ~22 degree edges according to him. The bone cutting is also done in the least stressful way in a very controlled manner. Simonichs Raven also has a ~22 degree edge, and a much more obtuse primary profile than on the Busse lines (sabre vs full flat), yet I don't see you jumping all over that knife.
Cliff has said these thick edges are needed to chop bone, a trait he seems to feel is essential in a "combat knife."
For bone contacts you need a steep angle more so than a thick edge, wood cutting is more thickness demanding as lateral loads are more likely whereas direct compression is the critical factor in bone chopping. As for what is essential for combat knives, that isn't my personal perspective, just a common one.
[Ron's bone cutting]
A number of the knives Hood has used have very thick and obtuse edges, the large TOPS knives for one have much thicker and more obtuse edges than the Busse ones from what I have seen and read. The primary grinds are also *much* steeper and far more shallow (though a number of full flat ground ones have come out as of late). The cutting ability in general thus lower. See for example Davenports comparions of an Anaconada (9") to a Steel Heart (7") in which the SH is able to out chop the much longer Anadonada because of the slimmer overall geometry. Same with my personal experience with the Steel Eagle (7"). I have not seen any descriptions of the edge geometries on many of the knives you quote which put them significantly less obtuse and/or thick than the Busse line.
-Cliff
