Cliff Stamp wrote: I just realized that I can do some sharpening experimenting, take pictures and record sharpness measurements a lot faster than doing the cut trials. It seems obvious in reflection that it might be worth while to look at a few over lays, see what tends to happen and do a select few trials. The behavior is also quite predictable as it follows the same equation every time, only the coefficients change, and thus even a short run of < 100 cuts can also be used to weed out various non-functional approaches. For example what are the properties of these finishes :
a) apex set with CBN rods and then, two passes with medium rods
b) apex set with CBN rods and then, ten passes with medium rods
c) apex set with CBN rods and then, two passes with fine rods
d) apex set with CBN rods and then, ten passes with fine rods
How do you think these would rank compared to :
-apex set with CBN rods
-apex set with medium rods
-apex set with fine rods
In regards to initial sharpness on both a slice and a push and edge retention on both?
Other than predicting the highest push cutting sharpness when the apex was set with the fine rods, I'd be hesitant to place bets. In a) to d) I guess you meant micro beveling as the jump in grids is so high the finer grids would probably not do much at the same apex angle with so few strokes? To get high push cutting sharpness I'd expect you'd need to be able to sharpen not only the tips of the coarse edge but also get into the valleys somehow, which is where the medium and fine rods will struggle, inflexible as they are, as long as you're not removing the coarseness altogether. In any case, I look forward to the results, should you test your new idea of faster data generation!
Cliff Stamp wrote:Here is the real danger though, which is the base concern in all measurement - are you measuring something which is relevant to the question you are trying to answer. Used carpet for example is very abrasive and in general will dull a knife edge far faster than hemp rope (by more than an order of magnitude) but it also does it by a different (but related) mechanism. It isn't then at all correct to argue that since performance was see on used carpet then that can be used to predict performance on hemp, or cardboard or to jump from hemp/cardboard to foods - aside from some carefully made generalizations.
Yes, I have run into the same problem with many different experiments I've run - doing them the hard way is too hard / expensive / slow and cutting the corners will make circles out of squares. Sometimes it's still useful, even if you can only conclude that the height of the square, if it was a square to begin with, couldn't have been smaller the the diameter of the circle. :)
Cliff Stamp wrote:I have tried at times to look at the trades as that is an obvious huge source of information, but the problem is that it is widely scattered and damage tends to be dominant over anything else. I still keep track of it, but it is very hard to draw conclusions from it. Just try sharpening knives for friends, change techniques and see how it influences how long it takes them to ask you to sharpen again. I find that this time can be influenced with things not at all related to what you might expect. Still though, it can be useful to get some perspective from people who really don't care about sharpening/abrasives/steels any more than you likely care about the type of paper you use to write down a phone number.
I've sharpened knives to my friends, but since I don't have any jig system at the moment, I don't do too much of it. As it is, the knives when I first get them have extremely thick edges and are dull as can be. Thinning the edges requires coarse stones and freehanding with them, scratches are hard to avoid. My old mother, on the other hand, has cheap old kitchen knives that I experiment with. Despite my advices she keeps on cutting against metal and ceramics and therefore there's always work waiting for me whenever I visit her. Once the knives are properly thinned, it doesn't take too long to fix the edges. If she were to cut on cutting board only, I'd have much less practice so I'm happy she does things the way she wants. :)
Considering data generation, my in-laws, who also benefit from my sharpening services, are a funny story. A reflection of times past, they each have a small paring knife sized thing, decades old, they use in the table to piece bread, peel apples, spread butter, a wide variety of things. I had sharpened their knives numerous times but always wondered how on earth they get so dull so fast. Then one of them revealed that after my sharpening they scrape the edge with a nail to dull it... The thing is, if your hands are a bit shaky and you use the knife to cut tough rye bread against your own palms, it can be too sharp.
I like these lessons as they remind me that the optimum and maximum are not the same thing, and that I cannot always predict all even the most important variables beforehand, even if I try my best. Therefore, what is left is the iterative process and lot of repetitions. Easy grindability is a friend here :)