Temper said:
Exactly. I have tested a Hollow grind, full flat utility and a full convex, all with similar stock and blade sizes and the full convex in my experience out cut them all.
What were the respective edge geometries? In general, those grinding convex blades tend to leave the edges far more acute, it isn't uncommon to have them be 8/12, and they sweep back fast into the primary of 3/5. In constrast most flat ground knives have edges at 15/20 and the primary grind leaves the edge much thicker, again not by some forces property of the grind, just a choice of the maker. Wilson for example grinds his flat ground blades to edges 0.005" thick and very acute, no problems with cutting ability there.
pict said:
I've noticed on the Mora SWAK's that I loan to my students that the edges will slightly ripple under impacts with hard woods.
The initial bevel on those knives is usually hollow ground, I have measured the edge at 1-2 mm back to be ground to 5 degrees and under per side, plus the hollow nature means it tends to focus lateral loads and induce twisting. Just grind the bevel off flat, it takes about 5-10 minutes with a really coarse stone on a small knife.
Paul Davidson said:
The skill of the user will change that performance as well as personal preferences, and that leads to bias.
No, bias can't be concluded so trivially, if this was the case for example you would call every experimental paper every published biased. All experimental data is always subject to user influence, in high school you are taught "ideal" principles and abstracts such as everyone should be able to repeat an experiment and get the same results if done "scientifically". In reality this means making statistical arguements and they are nontrivial because the user does always influence the results and same actually means something like "low probability of signficant statistical difference", and even then there are user choices in what the tolerance is for low and significant. However none of this means you simply throw up your hands and say everything is just opinion and it is all subjective. Well you can, but you don't have to, Mike Swaim and Joe Talmadge didn't and they had a massive influence because of it, as did countless other people like Alvin Johnston, Phil Wilson, Wayne Goddard, etc. .
Better is a matter of performance, but also preference, fashion, and opinion.
If you want to discuss aesthetics then that is all personal opinion, but performance isn't. Yes it will be influenced by personal characteristics and skill, but these won't have the types of influences which would favor that grind. It isn't a subjective issue, and isn't even a complicated one. Consider a 1/8" scandinavian blade with a typical 10 degree bevel on a one inch wide stock to a 3/16" fully flat ground blade on the same stock.
The flat ground blade is far stiffer and stronger, is actually lighter, and the edge is actually thinner and more acute up until you are way past halfway on the blade. Thus it cuts better, the edge is more durable, the blade is more capable of prying, it is lighter in hand and to carry, and sharpens far easier. None of this is subjective, they are all basic facts of mechanical principles and if you removed them from the hype of the scandinavian bevel and discussed them in general they would not be debated.
The single bevel has one advantage, it is cheaper to make. It is inferior in all other aspects. Even if you do for some reason actually like the wide bevels, for sharpening as is often noted for example, you can keep this and increase the perforamnce signfiicantly by using hollow relief grinds such as used by the Japanese to evolve the design, another culture of knife users, of which there are many.
-Cliff
(usually the learning cycle includes some broken blades).
