So I am not the most experienced guy here and 100% NOT trying to start an argument. With dedicated choppers, what you are saying makes sense. However, when you do stuff other than just chopping, like carving or battoning, you inevitably "twist or roll" the edge and put lateral / torquing force on the edge. In that case, doesn't it make more sense to have a slightly more obtuse edge?
My sample size on this is pretty small. However, I put a 15 dps edge on my Condor Kephart. It promptly rolled in a few places from just basic carving. However, at 20 dps it held up fine. My BK9 is used only as a chopper. It has a 10 dps mirrored edge with a tiny 20 dps micro bevel (done by Josh at Razor Edge), and it has held up great... I am not sure what all that proves, but I know I am nervous about going below 18 dps on a user.
BTW, i like your collection of big knives. Nice pics!
Thanks!
Generally I find 12 degrees per side is still stiff enough to not roll under moderate use, and under chopping when keeping the pull-out effort straight: Remember 12 degrees per side is still a pretty stout 24 degrees inclusive v: Not that weak, but anything below 15 per side is where the steel begins to be a real factor under heavy tasks...
I have had work done by Josh (fantastic guy to deal with), and I do agree that 10 degree per side is borderline... I think 12 is ideal while what I saw of Josh at 15 degrees per side is good but on the high side... A polished 15 is still very impressive for slicing paper, but my philosophy is this: It is better to have a thinner angle to start with, because touch ups will open this up anyway...: That incredible "new" 15 per side performance will be utterly gone by the time it is touched up even just once...
What is important to remember is that going below 15 per side
will separate the knives quite starkly: Whereas gradual wear at 20 per side seems to make all steels more or less equal, and hard to differentiate, damage at borderline thinness separates the good steels from the bad
very quickly: Custom knives I have had by Neeley, Andrew Clifford and even RJ Martin showed signs of
not taking thinner angles: RJ Martin's S30V has micro-rolling even at near 20 per side(!), Neeley's 440C crumbled no matter what, and ACK rolled when very thin: Note that, all this while, doing more heavy work at thinner angles, Randall and Lile were like bullet-proof unkillable tanks in comparison...
Quite frankly I would
not expect a low-priced BK-9 to hold up at such low angles, even if it does well at the 17 per side it comes with.
A second factor for rolling edges, after edge angle, would be edge thinness: I find the 0.5 mm (0.020") that Randall uses ideal. Even 0.030" is borderline for slicing ability on big knives in my opinion, and I had to put a high bevel height on my Lile to make it acceptable.
0.5 mm is still the thickness of the skin throughout a WWII fighter aircraft... In steel, that is a
significantly stiff thickness, yet most big knife edges are
double that, some, like Neeley's SA survival knives and the Boker Apparo, are
triple that (which makes the knife practically useless for slicing)... The BK-9 is just under double the 0.020" value, if I remember, but 17 per side is actually better than most factory fixed blades angles, which are often a ridiculous 25 per side... I liked my Bk-9 but hated the careless heat warping looking down the spine... Compared to a Randall Model 12, the Bk-9 will perform just over half as well at chopping (compare the Model 12 to the Chris Reeve Jereboam in the pics above: The Jereboam was very close to a Bk-9), and this shows just how much the edge thickness affects chopping performance
far more than edge angle...
I think 12 degrees per side and thin 0.020" edges make sense on big knives, because on big knives the edge is further from the hand, so the slicing effort on small tasks is greatly increased: Although whittling is seen as a "light" task, in fact, above 12 degrees per side and 0.020" in thickness, whittling can become a major physical effort with a big knife...
I is true thin sharp edges of 0.020" and 12 per side, will yield almost no chopping benefits: A 0.040" and 20 per side edge will chop almost as well, and do as well or better at other heavy abusive tasks: But this is where I depart from that "safe" 20 per side angle: My interests is in "Survival Knives".
Whatever "those" may be, these knives by definition have to do
everything well in my book...: To me they are like the fighter pilot who has to be a navigator/radioman/bombardier/formation lead/commander all rolled into one guy: This means the guy in question is simply better and more extensively trained than each of the "specialists" in a bigger aircraft: Just because he has to do everything doesn't mean he can get away with doing anything badly...
So given the length of leverage a big knife has fighting against you on small tasks, and the fact that small tasks do require an underrated level of physical effort even for whittling, in my opinion the "Survival Knife" has to be thinner-edged than a "dedicated" chopper would feel safe being... The "Survival Knife" thus has to be of a superior quality steel at the edge to take on all tasks despite extreme thinness: I have found the differences in thin edge toughness quite stark, even on customs costing thousands, and generally my experience has been that paying through the nose has helped in getting a knife that does well on heavy tasks despite thin edges (Unfortunately)...: Randalls are actually the
cheapest I have found that will do this well, and so are really a bargain at $900 for a Model 12 (which is also better made and more symmetrical than a lot of their other knives for some reason, like their 18 style blades, which are way too light for chopping anyway)...
Other brands I can recommend are the 2 grands range(!) Liles and at least one near one grand Colin Cox model... I will soon try out a Steve Voorhies, but those are carbon steel mostly (Carbon steel is simply less able in
all categories than a top-end stainless like 440C -440/Aus-6/8 being still unmatched for versatility/performance in various materials imho-, except for the ease of sharpening with a stone)...
Unfortunately in the do-everything category, I don't think there are many thin-edged big knives that are bargains much cheapers than Randalls... Big Al Mar knives could be an alternative, but I only tested them lightly and they are all old and OOP, and not cheap when you find them...
At thin angles, it could be the maker's care for getting extra-clean steel billets makes all the difference in combining heavy tasks with thin edges...: I know Randall are really on top of this, and it could make all the difference...: Seki-City blades also seem very good on this: I always look for Seki-made over anything else from Asia... Also, heavy re-profiling by hand is awful and tiresome, but it always beats power tools to keep the temper at the edge apex the way it should be...
Gaston
