how do you get a toothy edge?

For machetes, I use a Hand-file. Form burr with coarse side and remove/sharpen with the fine side. For knives I stop as low as a Norton Coarse India or Coarse Economy stone. These edges are somewhere in the 100 grit range, give or take.
 
Yup. A smooth cut Swiss file and a little skill will give a great working edge and is easy to touch up.
 
a toothy edge is not as sharp as a smooth edge. depending on the definition of "bite" a toothy edge has also less bite.
see for example scalpels, disposable shaving razor blades.
also true for cutting tomato skin, best done with a smooth edge!

there are socalled tomato knives on the market; they have mini serrations (or mini teeth) which bite like any serrated edge and stay longer "sharp". but micro teeth, nano teeth, they reduce the sharpness and cutting performance in every respect!

you can test by trying to cut into your finger skin. a toothy edge will just fail to do it. compare with the cutting performance of the smooth edge.
 
kreisler said:
a toothy edge is not as sharp as a smooth edge. depending on the definition of "bite" a toothy edge has also less bite.
see for example scalpels, disposable shaving razor blades.
also true for cutting tomato skin, best done with a smooth edge!

there are socalled tomato knives on the market; they have mini serrations (or mini teeth) which bite like any serrated edge and stay longer "sharp". but micro teeth, nano teeth, they reduce the sharpness and cutting performance in every respect!

you can test by trying to cut into your finger skin. a toothy edge will just fail to do it. compare with the cutting performance of the smooth edge.
Click to expand...

I am not sure how seriously (or not) to take your post.

1. I understand a toothy edge is not as sharp in relative terms as a smooth edge. I did not ask in my post which one was sharper. I asked how to achieve a toothy edge.
2. I have always found a toothy edge gets through tomato skin easier than a smooth edge. It may not cut thin slices as well, but I don't understand your claim here, when you go on to use a serrated blade as an example. What is a serrated blade if not just a very large tooth?
3. "Test by trying to cut into your finger skin..." Now you are just talking crazy. What on earth do you mean by this? You cannot seriously be suggesting to cut yourself as a test of knife sharpness, so what are you saying.

Your link to the other thread simply goes to a post about a disposable razor blade holder that you made and claim to actually use. For one thing, that modified disposable razor looks genuinely unsafe to handle. I am somewhat shocked that you are actually proposing in that thread that other people attempt this.

Nevertheless, I made no statements about, or comparison to a smooth edge, but your post is a very limited description of a disposable blade and how it is very sharp. What is your point?
 
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The point of my post is to question why one would want a toothy edge in the first place, i.e. an apexed edge with micro or nano teeth. I've seen several claims on the inet, even by the Edge Pro Apex maker claiming that for certain cutting tasks like cutting a tomato skin, a toothy edge would cut or bite better. In my experience the opposite is true, namely the less toothy the apexed edge the bitier the apex becomes (as witnessed by commercial examples a scalpel or a disposable shaver)! Never mind then.

If your experience is that a toothy edge cuts better for your tasks, then okay. There are conflicting or contrary experience reports then. Yes a serrated blade is comparable to a macro toothy edge (well, the difference is that the former is sharp along the entire edge whereas the latter isn't sharp between the teeth) and a knife with commercial mini serrations will have extraordinary bite because of them.

How to create a toothy edge? Apex the knife edge with a low grit stone (180#), then break off the burr. To make sure that the finest microscopic burr bits are gone, remove them with a leather strop (the leather strop doesn't even need to be loaded with compound). Done. Since the edge has been apexed, it will be nice cutter in practice no matter what.
 
I will take a toothy edge (325 or so) in the kitchen all day long. I guess the only way to see what you like is to try both and see which you prefer. That's exactly what I did.
 
In the kitchen I want my Chef's knife with a pretty polished edge since it mostly is sued for chopping, dicing etc. My utility and paring knives are toothy - it works better with offhand cutting.
 
For kitchen use, I've liked thin & polished edge geometry best. For tomatos & such, the thinner geometry and a fully-apexed edge make most of the difference, regardless of chosen edge finish. The toothy edge can help 'bite' the tomato though, if the edge geometry is thicker / more obtuse, or somewhat short of a complete apex. But with a very acute edge, like sub-30° inclusive, the narrow geometry and a crisp apex will render the finish choice almost moot in kitchen use. Use what you're comfortable with, in that case.
 
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^^^More importantly, it looks like you can crack open a cold one with that serrated blade. Puts me in the mood for one right about now...
 
I guess a little more detail is needed. I typically make a light cut into the fine side of my Norton Economy stone to remove damaged metal and establish a tiny flat I can barely see as an even starting point. If the edge just needs sharpening, I do 10 to 20 passes per side and check for either the tiny flat to be gone or a burr. When checking for a burr, one needs to check from the other side to be sure its smooth. Cutting into the stone like I do will leave what feels like a burr on both sides at once, and that can fool you.

The next step is removing the burr. I elevate the angle and make very light alternating passes on the coarse or fine side of the Norton stone. 10 to 20 passes per side will usually do it. After this treatment, my kitchen knives will treetop arm hair and whittle beard hair, and will level off the fingerprints on my thumb, taking down just the apex of the ridge.
 
Try using a scythe and the toothy vs. polished dynamic becomes VERY obvious. But you can also test it very easily. Polished edges yield longer edge retention and higher overall performance in pushing cuts. Crisply-apexed coarse edges yield longer edge retention and noticeably more bite in slicing cuts, and the bias of the scratch pattern affects the aggression in a readily observed manner. It's about striking the balance along the toothy/polished spectrum for your range of tasks.
 
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