Taking sharpness to another level.

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Depending on what you're cutting, there's also such a thing as "too sharp."

What happens, when the surfaces adjacent to the cutting edge are too smooth and polished, is that you get a "vacuum" between the mirror-smooth surface of the cutting tool, and the mirror-smooth surface of the workpiece. This causes the cutting tool to become "sticky" due to the vacuum and braking effect of friction. (This vacuum is also how insects can land on glass ceilings and "stick" to them.) It's also why some wood planes have soles that are grooved (although the conventional wisdom now is that grooved sole planes are unnecessary) and why knives for cutting roast beef have divots cut out of them.

The "stickyness" caused by this vacuum can be amazingly strong. If you got two 12" x 12" plates of rigid steel and were able to put a perfectly smooth and planar surface on both of them, and then stacked them on top of each other, so that all the air was squeezed out from between them, the only way you could get them apart is by sliding them, one over the other, and even this would be very difficult due to braking friction. And the 14.7 psi of atmospheric pressure pushing them together from both sides (12" x 12" x 14.7 psi = over a ton of force on each side) would make them impossible to pry apart by hand.
 
Most wood is porous. Think it might make a difference with wet wood?
Don't know, but with a chainsaw, I doubt it. On the other hand, I do know that a hand plane is "stickier" on green wood than dry.

I was commenting only on a "general" level. Some people go overboard on the sharpening thing, and seem to think that "sharper is better" under every conceivable circumstance, which I contend isn't always necessarily true. I also disagree that "a finer edge lasts longer than a coarser edge." Seems to me that's pretty obviously untrue. Otherwise jackhammer bits and the teeth on bulldozer blades would be sharpened to a razor's edge.

That said, I am a woodworker and am well aware of the advantages of, and very much a proponent of, sharp cutting tools. There comes a time, though, when it's time to put away the sharpening equipment and the scanning tunnelling electron microscope and actually cut some freakin wood. I would argue that this time comes long before sharpening a chainsaw chain to 10k grit. Thirty hours spent sharpening one chain that'll be wiped as soon as it hits a few grains of sand ain't my idea of "fun," but hey, whatever floats yer boat...
 
The 'micro-bevel' thing, however, may have merit. For those not familiar, many woodworking chisels, gouges, and plane blades ('irons') are sharpened at a primary angle / bevel, then finished with a slightly steeper 'micro-bevel'. When maintenance sharpening is done, only the micro-bevel is touched up, instead of taking off all the steel required to bring the primary bevel to a fine edge.

I have often wondered if this could be applied to saw chains, especially square filed cutters, possibly by using different files than those used to shape the cutters: perhaps something like a feather file, warding file, the back of a single bevel file, etc. Clearly, this would take a bit more skill than running a '2-in-1' guide past the tooth, or maybe it just requires running a file one size larger past for a stroke or two on round filed chains?

In addition to being faster, due to removing less material, it would present a stronger cutting edge, and perhaps make the cutters last longer?

Anyway, just an idea to keep @Gaudaost from sleeping tonight!


Screen shot 2021-02-15 at 1.48.09 PM.png

Phlbert
 
So....microbevels actually decrease edge-holding ability? That's a new one on me. Maybe we should be using razor blades on our lawnmowers and axes. Even microtome blades -- used for cutting microscopically-thin slices of animal tissue for histology -- have secondary bevels.

I guess the "finest" edge you can get is the wire edge that forms when two planes intersect in steel ... but the wire edge doesn't last very well at all. You can break it off with your finger. I'd rather knock it off with a microbevel (jeweller's rouge on a piece of MDF) than let it break off on its own, since the microbevel will be more durable and will be sharper than the jagged edge that's left when the wire edge is broken off the first time you use the tool.
Hi, I never said micro bevels decrease edge holding? I think you are getting confused.

A wire edge is a misnomer - it isn’t an edge at all, it’s a wire burr, which forms when you apex two bevels giving an indication of a primary bevel - here is a coarse burr just formed hanging off the apex on one of my carving knives.

5FB17FE8-216E-42B2-89DF-AF5E7B79D5E9.jpeg

I agree - breaking off any burr is a bad idea, it should be taken up through the grits until it’s much thinner than a human hair and finally polished away. Breaking off a coarse burr will leave a serrated edge decreasing sharpness and cutting ability.

It’s worth mentioning in reply to your other post. morakniv lamanited knives have relatively poor edge holding ability’s and aren’t even close to 65 hrc - they are a 58-60 HRC insert. They are great for the fact that they are nicely profiled, have nice shaped wooden handles and are accessible, but leave much to be desired in terms of edge retention. As a reference, the z-wear carving knife in developing holds an edge over 24x the length of a morakniv laminated blade, it’s still a carbon steel, but with the addition of vanadium and a few other elements.

You also asked about compounds and grits.

I sharpen up to 10,000 grit with SiC papers and then with carving tools use a 0.5 micron / 60,000 grit diamond stropping compound on my own kangaroo leather and suede strops.

Here is a batch of sharpening systems about to be wrapped and sent around the world.

8D75D43E-C33F-4BBD-A800-0465AC9E58E5.jpeg
 
The 'micro-bevel' thing, however, may have merit. For those not familiar, many woodworking chisels, gouges, and plane blades ('irons') are sharpened at a primary angle / bevel, then finished with a slightly steeper 'micro-bevel'. When maintenance sharpening is done, only the micro-bevel is touched up, instead of taking off all the steel required to bring the primary bevel to a fine edge.

I have often wondered if this could be applied to saw chains, especially square filed cutters, possibly by using different files than those used to shape the cutters: perhaps something like a feather file, warding file, the back of a single bevel file, etc. Clearly, this would take a bit more skill than running a '2-in-1' guide past the tooth, or maybe it just requires running a file one size larger past for a stroke or two on round filed chains?

In addition to being faster, due to removing less material, it would present a stronger cutting edge, and perhaps make the cutters last longer?

Anyway, just an idea to keep @Gaudaost from sleeping tonight!


View attachment 889907

Phlber

haha all good mate :) I got this in the morning :laughing:

Just to clarify, though I like the picture it’s actually the other way around, woodworkers tend to add an optional relief bevel after sharpening a tool, rarather than an optional micro bevels of which would increase the primary angle (not ideal)

it’s done for the one and only benefit of only having to remove less steel for the next sharpen, it’s not for edge stability or strength.

In fact I use a similar technique I call flat over hollow. Essentially creating a hollow grind in a tool followed by sharpening it on a flat surface gives two things, more positive engagement of the bevel and less steel in which to have to remove, essentially the same as relief bevels :)

Here is a picture of my carving knife with the same concept applied in a different technique:

Note the hollow ground finish on the inside compared to the highly refined and polished “tram line” style flats

A0BB96B8-4D08-4B67-BF60-36075FB426FA.jpeg
 
So, how about micro-bevels (or relief bevels) on these edges?

View attachment 889978

Philbert
Firstly, that’s absolutely stunning, is it yours and was that ground or freehand filed?!?

As for relief bevel, I’m intrigued by the idea and concept for sure! Though I wonder how difficult
It would be to get under the tooth to add one vs the benefit in speed to resharpen as we only use one file rather than multiple grits to form the edge.

i’d love to see someone attempt it for sure!
 
smaller wood chippers use a bevelled edge on their blades for edge retention, learned this hand sharpening them..45 as the main angle hollow ground then approx 35 as the bevel. hand sharpened one on a stone to 45 degrees removing the bevel(took tons of work being hardened steel) and ran it..edge lasted a hour then was useless dull...resharpened to 45 then beveled the edge to 35 and it stayed sharp for over 6 hrs. I could see it being applied to a chains chisels but the drawback is added time spent doing it and likely needing a jig or angled template to check your work.
 
Whose knive sharpening machine are you using. Looks a lot like an edge pro.
These edge pros are kinda cheaply made. I'm now on my third, but no longer use edge pros or clones of the same. I found a good one that clamps onto the blade and then spins for doing the other side. Simpler and faster with more angle consistency.
 
Hi, I never said micro bevels decrease edge holding? I think you are getting confused.
Here's exactly what you said:

for typical high carbon steels a fine edge lasts longer than a coarse edge

Please explain exactly how "a fine edge lasts longer than a coarse edge."
Feel free to use drawings, geometry and metallic grain structure diagrams if you want.


It’s worth mentioning in reply to your other post. morakniv lamanited knives have relatively poor edge holding ability’s and aren’t even close to 65 hrc - they are a 58-60 HRC insert. They are great for the fact that they are nicely profiled, have nice shaped wooden handles and are accessible, but leave much to be desired in terms of edge retention. As a reference, the z-wear carving knife in developing holds an edge over 24x the length of a morakniv laminated blade, it’s still a carbon steel, but with the addition of vanadium and a few other elements.

"Holds an edge 24X as long as a laminated Mora" LOL, that's pretty funny. All I can say is that I've used some good steels (including top-shelf high-dollar Japanese chisels, as well as ceramic knives) along with the Mora, and the Mora held an edge longer than anything I've ever used. Do you own a Mora laminated knife? Do you skin many animals with it? I've used many, many different steels in both woodworking and "animal carving" ... and sorry ... but your claim of "lasts 24X as long" sounds like a whopper, In my experience, there simply aren't differences that big, even if you compare "middle of the road consumer grade" with "best steel in the world" grade. It sounds like you're selling snake oil with some of these fantastic claims, TBH.

For example, your claim that "After 30 hours of carving it still split an unsupported hair," sounds an AWFUL lot like the folklore in James Clavell's novel "Shogun" about the samurai sword that was supposedly so sharp that if a silk scarf was dropped on top of it, the sword would cleave the silk scarf in half without even disturbing the speed of its fall due to gravity...LOL

Tell us about your spoon carving knife that's sharp enough to carve telepathically... :laugh: "It scares the wood so much that the spoons carve themselves out of fear!"
 
Here's exactly what you said:



Please explain exactly how, and in what alternate universe, "a fine edge lasts longer than a coarse edge." Feel free to use drawings, geometry and metallic grain structure diagrams if you want.




"Holds an edge 24X as long as a laminated Mora" LOL, that's pretty funny. All I can say is that I've used some good steels (including top-shelf high-dollar Japanese chisels) along with the Mora, and the Mora held an edge longer than anything I've ever used. Do you own a Mora laminated knife? Do you skin many animals with it? I've used many, many different steels in both woodworking and "animal carving" ... and sorry ... but your claim of "lasts 24X as long" comes across as absurd. In my experience, there simply aren't differences that big, even if you compare "middle of the road consumer grade" with "best steel in the world" grade.

In fact, a lot of the stuff you're spouting here sounds a lot like folklore...Your claim that "After 30 hours of carving it still split an unsupported hair," for example, sounds an AWFUL lot like that fable in James Clavell's novel "Shogun" about the samurai sword that was supposedly so sharp that if a silk scarf was dropped on top of it, the sword would cleave the silk scarf in half without even disturbing the speed of its fall due to gravity...LOL
I’m not going to keep correcting you and having a pissing match on here. Do some research on me, my business, background, contact Tormek and Morakniv who have both sent me many products over the years for testing and follow my social media. I have around 42,000 people who follow what I do, thousands of customers world wide of my sharpening systems and a 15 week waiting list. I run my own sharpening and carving business and have customers all around the world sending me their wood carving tools to repair and sharpen. My social media has countless videos on the z-wear with many hours of live demos, information on the steel, it’s micro structure and elemental content, Romans process for treating, refining and processing it.

Ultimately you can believe whatever you wish, but I’m not going to spend time trying to convince you of something or justify anything to you. I go off facts through testing things myself, science and have built up a reputation based on honesty, skill and experience. With a little time and reasearch you’ll realise just how silly / ignorant what you’re writing is.

Here is that video -

https://www.instagram.com/tv/CAUdGY2j7ni/?igshid=482r6bpa4inj
https://www.instagram.com/p/CF7HcW6juak/?igshid=r337y7tk27e8
I’ll leave it there.
 
OK, fair enough. But one last time (I ask in all honesty as a woodworker who wishes to seize the grasshopper from your hand and thereby know more):

How can "a fine edge last longer than a coarse edge"? Serious question. Because if I could find a way to do this, I would be all in favor of doing it. It sounds like you know far more about it than I do, and I would like to benefit from your knowledge.

Even if you don't have the time or patience to explain, please just give me some clues on what to Google. Because your statement "a fine edge lasts longer than a coarse edge" contradicts everything I know about steel or, for that matter, physics.
 
OK, fair enough. But one last time (I ask in all honesty as a woodworker who wishes to seize the grasshopper from your hand and thereby know more):

How can "a fine edge last longer than a coarse edge"? Serious question. Because if I could find a way to do this, I would be all in favor of doing it. It sounds like you know far more about it than I do, and I would like to benefit from your knowledge.
When I say a fine edge it’s in reference to the amount of refinement it has gone through. For example, an edge sharpened to 10,000 grit is finer than 1,000 grit, not in relation to the bevel angle / apex being fine / thin / reduced.
 

That is an absurd price. Clones of the same cost $20 to $30 and work just as well, but they do fail fast (dozens of knives). Still it is far more economical to buy clones and replace them regularly if your sharpening pace keeps steady.

I swear by this now.

61JGauth8PL._AC_SL1200_.jpg


https://www.amazon.com/RUIXIN-PRO-P...jbGlja1JlZGlyZWN0JmRvTm90TG9nQ2xpY2s9dHJ1ZQ==
Which is now selling an almost 1/2 what I paid. The clamping once and being able to do both sides of the edge is all you need to know to realize that Edge-Pro is archaic.
 
When I say a fine edge it’s in reference to the amount of refinement it has gone through. For example, an edge sharpened to 10,000 grit is finer than 1,000 grit, not in relation to the bevel angle / apex being fine / thin / reduced.
OK, thanks. I thought you were referring to bevel angle, which is what led me to the microbevel/secondary bevel stuff.
 

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