Sometimes we can miss the obvious

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Gary W. Graley

Gary W. Graley

“Imagination is more important than knowledge"
Knifemaker / Craftsman / Service Provider
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Mar 2, 1999
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Sharpening, I've sharpened I don't know how many knives over the past decades, but it's a sizeable amount to be sure. And while they are sharp, I only recently 'discovered' about what a toothy edge is and one way to create it. A few years back I had a neck knife made by Alex Horn, apprentice to Murray Carter. It was a very well made knife and one of the keenest edges that's arrived from a maker that I've seen in a while. Quite toothy/bitey kind of edge, really cut quite well. Drift forward a couple of years and the other day I saw a youtube video showing some comparisons between toothy and polished edges and my take away from that was what the title of the thread is hinting at.

The closeup look at the edge grind, the striations were perpendicular to the edge, so all the scratch pattern would create straight up and down micro grooves along the edge, which leaves a very toothy edge.

I had always swooped along in order to get all of the blade sharpened on the stone, but I tried to keep the edge going perpendicular to the side of the stone so I would make straight scratches along the edge. As a result I liked how the blades edge felt and cut after a short time on the stones. And I did not bother trying to fully strop the edge, but just lightly stropped and kept it at the same perpendicular position as I had when sharpening. In other words, I wasn't smooshing the edge in an arc, but kept the scratch pattern as in tact as I could and finally strop on some denim to remove any stropping compound.

The results were great, the edge sliced through paper towels cleanly, would shave hair easily and slice paper but with a little more noise than a mirror polished edge bevel.

Now, mirror polished edge bevels are neat and probably have their place, such as wood cutting/wood carving you need a very sharp polished edge bevel to produce good results on your wood project, talking knives/plane blades and chisels. But for an EDC type blade, the toothy edge I think certainly has some great benefits, no skating across the material you want to cut, it just starts digging in right from the get go. One 'Test' is on some foam, letting the weight of the blade slice across the foam, if it's not toothy it will just glide and not cut in, but a toothy edge will sink in and start cutting, especially helpful in the kitchen of course.

So, while this I'm sure is old news for a lot of you died in the wool sharpeners, there may be some that struggle and this might be of help.

Ok, enough, now to see what knives in the kitchen need touched up ;)
G2
 
Appreciate the post. Different perspectives on sharpening always help add to the arsenal of techniques.

I need my blades to cut. I’ve modified my sharpening methods over the years. Focusing more on keeping my sharpening time more efficient and effective. I rarely use anything past a medium grit stone anymore when sharpening. My fine stones are for that quick touch up or quick micro beveling.

I’m definitely going to try what you mentioned next time I sharpen. Sounds like an edge I’m looking for.
 
Thanks, one thing that I have is the Worksharp guided field sharpener, set at 20 degrees so it's you keep that angle when you start out, and I tried my 'new' style using that and it worked well, as with any diamond plates, you really have to remind yourself to let the diamonds do the work, don't apply a lot of pressure or you will end up with a shiny metal plate ;)

See details here at the Knife Center site for this one


G2
 
You might want to read The Razor Edge book of Sharpening by John Juranitch. It's now free online. He argues that toothy edges do not perform as well as smooth edges. He did a lot of electron microscope work and A/B comparisons to prove it.

I've always liked a clean, smooth, polished edge, but I've never tried any kind of reasonable comparisons. Lots of people like toothy edges, though. I'm still thinking this through.
 
Thanks I’ll check into that book
G2
 
Hello G2. Thank you for your posts and info.
Maybe like you, I've had knives and sharpened them adequately for many years. However, for the last 2+ years I've been trying to learn about steels, their composition, blades and their geometry, etc... and how to sharpen/hone them using different abrasives and learning about the resulting differences in the edge/apex.
I've enjoyed this and find it very interesting.
I'm beginning to have a better appreciation for knives and their intended uses and what types of sharpening/honing are better suited for each.
I've been trying to do this somewhat systematically using low alloy, high carbon steels and various types of abrasives.
Thank you for sharing!
Best regards and God bless.
 
This is something I'm currently exploring. I bought Mrs. McGee a small 5" high carbon steel kitchen knife. It was built by (IMHO) a fairly reputable mass-production company, and was on sale dirt cheap. I figured I had nothing to lose. Mrs. McGee chopped about 1 potato with it, handed it over and declared, "this needs a new edge." (I think she's decided that she likes having sharp knives in the kitchen....) Anyway, I put it on the Hapstone and ran it through 200, 600, and 1000 grit diamond plates. Seemed plenty sharp, sliced paper like butter. But when I put it to work on a tomato, it wanted to slide across the skin. Once the skin was broken, it sliced very cleanly. All I could figure was that I needed the edge to be toothier, so I put it back on a coarse stone over the weekend to make that correction. It seemed to do much better with the tomato skin after that.
 
You’re most welcome and I find your post interesting and I’ll bet it is enlightening to try out various steels
That plus how different companies do their heat treatments would be key as well.
I remember Jimmy Fikes telling me that sometimes people use round ceramic rods to sharpen with and it can end up fracturing the very edge and producing small chips in the edge. He said that it was not unlike how the flint knapping is sharpened by pressure to break the edge to reveal a new sharp section. So some steels if they are at a high hardness could experience chipping, something to keep in mind
Thanks
G2
 
Twindog said:
You might want to read The Razor Edge book of Sharpening by John Juranitch. It's now free online. He argues that toothy edges do not perform as well as smooth edges. He did a lot of electron microscope work and A/B comparisons to prove it.

I've always liked a clean, smooth, polished edge, but I've never tried any kind of reasonable comparisons. Lots of people like toothy edges, though. I'm still thinking this through.
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Polished edges are superior for pushing cuts, such as those used for chisels, axes, many wood carving knives, razors, and so on. Toothy edges are MUCH preferred in tools used for slicing work such as meat-cutting knives, scythes, utility knives used for cutting cardboard or rope, etc.

It's worth noting that the bias of the scratch pattern affects its slicing aggression. It's much like the rake angle on saw teeth. This is why scythers are taught to work their strokes from heel to toe, so they slant forward into the cut for maximum effect.
 
Thanks and I can see how that affect the cutting action
I checked on line but didn’t locate the book but I’ll see if my local library might have it
G2
 
FortyTwoBlades said:
Polished edges are superior for pushing cuts, such as those used for chisels, axes, many wood carving knives, razors, and so on. Toothy edges are MUCH preferred in tools used for slicing work such as meat-cutting knives, scythes, utility knives used for cutting cardboard or rope, etc.

It's worth noting that the bias of the scratch pattern affects its slicing aggression. It's much like the rake angle on saw teeth. This is why scythers are taught to work their strokes from heel to toe, so they slant forward into the cut for maximum effect.
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Yes, I know that's the conventional wisdom, and you have lots of really smart knife people who think like that. If I remember correctly, Ankerson stopped at 400 grit. And he got great results.

Juranitch was also a really, really smart knife person who calls that conventional wisdom nonsense. And he was serving meat cutters as a major, if not the major, part of his sharpening business.

From his book: "...because everything we had ever read on sharpening told us about these little teeth on our edge. As we got into our research, though, that idea of teeth turned into nonsense. Why were the dull edges the only ones you could feel these so-called teeth on? When the edge really cut slick, why did it feel smooth? How come you don't have to 'saw' the whiskers off your chin?"

After much study and examinations with a 10,000-power magnification electron microscope, he found that sharp edges cut the best and the sharpest edges had no teeth. None.

But as I said to Gary, I'm still sorting this issue out in my own head. I don't use a bread knife on my homemade bread. Never needed one. I do use a bread knife to cut insulation.
 
I've been aware for awhile, of the effects of my own diagonally-sweeping habits on stones, and how the resulting raked scratch pattern on the edge affects some of the cutting chores I do everyday. Most everyday, for myself and for family members, I chop or slice some veggies on a cutting board to be added to our lunch. I've noticed the difference in seeing the bias in the edge for a sort of 'push-slicing' cut, i.e., it's more aggressive if I subtly push the tip of the blade away from me, while chopping. If I do a draw slice, i.e., pulling slightly toward myself in the cut, I notice a subtle loss of aggression in the cut. So, doing this nearly everyday, it's frequently on my mind and gives me some motivation to experiement with my sharpening a bit, when touching up the kitchen knives.

I have a lightweight Buck 110 with a Zytel/FRN handle, that I picked up at Walmart for about $20 a while back. I've found that blade to be one of my favorites after setting the 25 - 30 inclusive bevels with a Coarse DMT hone and then adding a very minimal microbevel at the apex, using the 40-inclusive setting on the Sharpmaker, with either of the medium or fine ceramic rods. That thing has taken and held a wicked, zipper-like slicing edge better than any other blade I've tried that method with. So, I'm growing ever more fond of such wicked-toothy edges and interested in doing that with more blades that are suited to it.
 
Albert-Einstein.jpg


"It's all relative."
 
As it says under my avatar

“Imagination is more important than knowledge"
a quote from that guy
:)
G2
 
I think that this is a great discussion! The very cool thing about this topic is that everyone can go out and test which edge they prefer. Sharpen a knife to a polished or toothy edge and see how well it cuts for them and then try the other edge type and repeat.
That way an individual can decide for themselves if the conventional wisdom holds true or not.

Very cool topic.
 
Twindog said:
Yes, I know that's the conventional wisdom, and you have lots of really smart knife people who think like that. If I remember correctly, Ankerson stopped at 400 grit. And he got great results.

Juranitch was also a really, really smart knife person who calls that conventional wisdom nonsense. And he was serving meat cutters as a major, if not the major, part of his sharpening business.

From his book: "...because everything we had ever read on sharpening told us about these little teeth on our edge. As we got into our research, though, that idea of teeth turned into nonsense. Why were the dull edges the only ones you could feel these so-called teeth on? When the edge really cut slick, why did it feel smooth? How come you don't have to 'saw' the whiskers off your chin?"

After much study and examinations with a 10,000-power magnification electron microscope, he found that sharp edges cut the best and the sharpest edges had no teeth. None.

But as I said to Gary, I'm still sorting this issue out in my own head. I don't use a bread knife on my homemade bread. Never needed one. I do use a bread knife to cut insulation.
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The issue is that they aren't really teeth. It's just a method of conceptualizing it that's easier for folks to understand. However, the undulation of a "toothy" edge is predisposed to rolling when push-cutting materials (especially if they're resistant) while continuing to cut with less force than required of a highly polished edge that has performed a similar amount of work because the undulation reduce the initial contact surface area and present themselves at a slant to the cutting medium.

I can tell you firsthand that the use of the "toothy" edge makes a HUGE difference in the cutting efficacy of scythes, and allows them to cut hard, light, waxy grasses that will want to slip off a polished edge that has performed even a little work. A major factor, however, being that coarse edges should still be completely free of any burr or wire edge, and coarse stones are more prone to forming such faults. I looked into the quote and he provides no information about actually testing these edges nor how they were produced. Cliff Stamp, meanwhile, had done a decent amount of experimentation with coarse vs. polished edges and his findings were consistent with my statements.
 
FortyTwoBlades said:
Polished edges are superior for pushing cuts, such as those used for chisels, axes, many wood carving knives, razors, and so on. Toothy edges are MUCH preferred in tools used for slicing work such as meat-cutting knives, scythes, utility knives used for cutting cardboard or rope, etc.
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Generally agree ... but if your knife is really sharp, cutting cardboard is more of a push cut than a sawing motion.
 
3D Anvil said:
Generally agree ... but if your knife is really sharp, cutting cardboard is more of a push cut than a sawing motion.
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It is, indeed, but the edge does not hold as long when polished vs. when properly set as toothy. I believe this is because the undulations present themselves to the cellulose fibers in a similar manner to a hay knife. It prevents them from slipping off the edge and instead causes them to catch and consequently sever.

Toolad.jpg
 
I think the finer/smaller the teeth the keener it would be, I just got in a small Pena flipper, it's edge was ok, but I took it to a 1k diamond hone and did the straight down the line kind of light sharpening, didn't swoop across, and then a very light strop and then a strop on some denim, bluejean leg ;), and it brought the edge to a really nice fine sharp toothy edge. I like how it will slice down through soft paper towels easily and still push cut through paracord, which I was just doing with it.

I'll continue to try this 'system' some more using finer grit stones but too fine you start to lose the bite I think, but, I'll see
G2
 
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