Insane performance boost in cutting ability!

[FTR-14c]

Here is one that I just finished that cuts like a laser. I took it from .22 to about .188 at the spine and thinned behind the edge considerably. The difference is night and day. This was delivered with an edge that would shave but between the heavy coating and thick grind it did not work very well as a cutting tool.




I used this jig I modified to keep everything even and strait. You are supposed to use it to sharpen like this:



It works horribly and the blade is all over the place so I went a little out side of the box. I added this 1"x 1" square on the inside to rest the spine on as a guide:



Now I can sharpen and remove material evenly with very little margin for error. The angle is adjusted by sliding it in or out.

 

[Spey]

Creative jigged sharpening, melding tool and mind through the hand ... I like it! ;-)

Does the jig hinge at the bottom allowing you to gradually introduce the blade to belt?

 

[FTR-14c]

Creative jigged sharpening, melding tool and mind through the hand ... I like it! ;-)

Does the jig hinge at the bottom allowing you to gradually introduce the blade to belt?

Yes, the wing nut on the lower right tightens the hinge and the whole thing slides in and out as well for lots of adjustment. In the photo its set up for flat removal as the edge is away from the belt. To set up for sharpening, it would slide out to desired angle with the edge in contact with the belt. Then I rest the spine on the jig strait up and down parallel with the belt and slowly introduce the edge to the belt. It is about as fool proof as it could get. The blade is locked in and can only go one way all the way around the belly to the tip, completely even on both sides. After the initial edge is set I blend it in free hand with a slack belt.

 

[REK Knives]

Here is one that I just finished that cuts like a laser. I took it from .22 to about .188 at the spine and thinned behind the edge considerably. The difference is night and day. This was delivered with an edge that would shave but between the heavy coating and thick grind it did not work very well as a cutting tool.




I used this jig I modified to keep everything even and strait. You are supposed to use it to sharpen like this:



It works horribly and the blade is all over the place so I went a little out side of the box. I added this 1"x 1" square on the inside to rest the spine on as a guide:



Now I can sharpen and remove material evenly with very little margin for error. The angle is adjusted by sliding it in or out.

Very ingenuous man!! That's awesome!

I love the viel... Wanted one for a whole but now I have my 2x72 water cooled set up 😊

 

[FTR-14c]

Very ingenuous man!! That's awesome!

I love the viel... Wanted one for a whole but now I have my 2x72 water cooled set up 😊

Thanks, Its amazing what a 5 cent piece of aluminum will do with a little thought.

I've had the Viel for about two weeks and absolutely love it. Its perfect for sharpening and light modification but I would think one would want something more for making knives.

 

[Gaston444]

Historical examples of utility knives generally are all quite thin stock. The overbuilt knife seems to have come into vogue as knife work diminished in daily use for most people so they lost the ability to assess tool geometry, and as a cosmetic selling point.

When in doubt, thin it out!

Very true, but very thin bladed, and consequently lighter knives, are no longer considered very attractive for people who are interested in cosmetic/collector value, or using knives for heavier tasks that were usually left for hatchets in the old days, where "knife work" meant strictly slicing... To me the more fundamental problem is a wrong standard for edge grind angles, rather than just blade thinness or thickness.

The edge angle has for a long time been tolerated as much more open than it needs to be in knives intended for "general" use...: Randall says in their litterature (which I am guessing hasn't changed since the 50s) that 20° per side is the recommended edge angle for sharpening all-around outdoor knives: That is 40° inclusive... I think this performs poorly even if, like Randalls, the "back bevel", or secondary grind, is quite thin at the edge because of a hollow grind (at least on a thin-edged Randall, putting in your own tighter sharpening angle is still an option, unlike some thicker edged blades)... A thin blade with a 40° inclusive edge is still underperforming in my view, and can still be hard to re-profile properly.

Despite this, most factory knives are delivered with far worse than 20° per side, often they claim 25° but in fact they are around 30° or even up to 35° per side, especially if the knife has any kind or "emergency/survival" application: 70° inclusive!!!! This includes a high end survival knife by a custom maker like Vaugh Neeley, showing how universal the high edge angle "precaution" has become...

Randall goes on to say that smaller edge angles are possible, but lead to deformations or edge failures under "hard" use. But what no maker seems to take into account is a vital fact, which is that a sharper edge angles reduce stresses on the edge, even under hard impacts. Cliff Stamp has said, correctly in my view, that he encountered no problems with large knives while chopping even hard wood, or at least softer woods, with edge profiles all the way down to 10° per side, 20° inclusive... This is in part because a sharper edge "relieves" its own stresses if the hit is square enough. But it does open a potential can of worms for makers dealing with careless or incompetent users... And so knife edges are compromised to a very low standard for a perceived "Joe Public"...

Maker reputation is probably why the 20°/40° standard is invoked, but the reality is that actual in-box fixed blade edges are far more open than that, often grossly so, and to me the thick secondary grinds and blades follow from this overbuilt edge angle "standard", not the other way around. Blades would naturally be made thinner if 10/20 was a more universally accepted edge angle (maybe with more use of deep hollow grinds for the more popular thicker blades): If 10°/20° became the industry standard, makers would have to thin the blades at the edge at least, or they would get these huge tall primary bevels, which would expose what they are doing wrong because it would look silly...

Gaston

 

[chiral.grolim]

Randall goes on to say that smaller edge angles are possible, but lead to deformations or edge failures under "hard" use. But what no maker seems to take into account is a vital fact, which is that a sharper edge angles reduce stresses on the edge, even under hard impacts. Cliff Stamp has said, correctly in my view, that he encountered no problems with large knives while chopping even hard wood, or at least softer woods, with edge profiles all the way down to 10° per side, 20° inclusive... This is in part because a sharper edge "relieves" its own stresses if the hit is square enough. But it does open a potential can of worms for makers dealing with careless or incompetent users... And so knife edges are compromised to a very low standard for a perceived "Joe Public"...

Maker reputation is probably why the 20°/40° standard is invoked, but the reality is that actual in-box fixed blade edges are far more open than that, often grossly so, and to me the thick secondary grinds and blades follow from this overbuilt edge angle "standard", not the other way around. Blades would naturally be made thinner if 10/20 was a more universally accepted edge angle (maybe with more use of deep hollow grinds for the more popular thicker blades): If 10°/20° became the industry standard, makers would have to thin the blades at the edge at least, or they would get these huge tall primary bevels, which would expose what they are doing wrong because it would look silly...

Gaston

Cliff stamp is wrong, and numerous users as well as makers have pointed out that going below 30-inclusive can be devastating on steels over a certain hardness and in other than very specific tasks, in other words Cliff's claims are irrelevant.
Here is Steve Elliot's tests for wood-planer blades, cutting very thin curls of wood with highly refined edges on A2 and CPM-3V and M2 blades, etc., blades featuring some of the highest edge-stability: http://bladetest.infillplane.com/html/summary_of_results.html

At this time I’m using a bevel with a total included angle of 34º, formed by a 31½º primary bevel and a back bevel of 2½º. The A2 blades show minor chips after planing cherry, so for harder woods a larger bevel angle may be needed.

The Academy Saws M2 blade and the CPM 3V blade resisted chipping at an angle of 32º and showed only the smallest amount of microchipping at 30º when planing cherry. The Hock A2 blade showed significant chipping at 32º and the other blades have not yet been tested at the more acute angles.

There is a recent thread here showing SEMs of straight-razor blades (good hardness, high stability) sharpened at ~10-dps and how much damage they sustain merely cutting through a sheet of paper, NOT ideal for work other than shaving or cutting soft materials. I can post images of my messed-up utility blades (box cutters) at 10-dps. It is a poor-performing angle for most tasks.

Edge "angle" is NOT the most important factor, it is edge thickness that matters most, as angle is merely a description of thickness. Thickness determines edge strength and stability through its cubic relation to stiffness - for every 2x increase in thickness the edge gets 8x stronger! In contrast, a 2x increase in thickness results in only ~4x decrease in cutting efficiency (depending on type of material being cut).

Most knives are ground at <5 dps for the primary bevel, thinner if given a hollow-grind, and have very tall primary grinds, that is normal. It is the secondary bevel where edge-angle comes into play. Using 30-degrees inclusive gives a height:width ratio of 2:1, lots of strength/stiffness. If you are experiencing poor cutting efficiency, lowering the edge-angle will produce a somewhat thinner edge but a dramatically lower strength at the edge, resulting in the common complaint of edge failure and the need for more sharpening. In contrast, if you lower the edge thickness instead of the angle, you gain dramatically in cutting performance without sacrificing edge-strength, because you aren't weakening the edge, only the blade itself, and most damage happens in the edge, not the blade.

Axes are sharpened to ~30 inclusive, chipper and chainsaw and chisel and planer blades are all 30-inclusive or greater, kitchen and hunting knives the same. What varies among these different cutting tools is not edge-angle, it is edge-thickness to provide more or less blade strength as needed for the application. Axes get thicker behind the edge because they need it. But your skinning knife doesn't need to. How many folk claim to sharpen below 30-inclusive but then add a microbevel ~40-inclusive? The edge performs better with that stronger geometry, not worse.

 

[sodak]

Edge "angle" is NOT the most important factor, it is edge thickness that matters most, as angle is merely a description of thickness.

I think this is a good point that might even warrant it's own thread. I have long had the view that thinning out the primary grind, then using a fairly large edge angle/microbevel works very, very well. Dozier does this with his knives, his high hollow grind is thin, but the edge angle is fairly large.

I used to say "obtuse" to describe the edge angle, but that's not right either.

 

[Gaston444]

Cliff stamp is wrong, and numerous users as well as makers have pointed out that going below 30-inclusive can be devastating on steels over a certain hardness and in other than very specific tasks, in other words Cliff's claims are irrelevant.

------------------------------------------

In contrast, if you lower the edge thickness instead of the angle, you gain dramatically in cutting performance without sacrificing edge-strength, because you aren't weakening the edge, only the blade itself, and most damage happens in the edge, not the blade.

----------------------------------------------

Axes are sharpened to ~30 inclusive, chipper and chainsaw and chisel and planer blades are all 30-dps or greater, kitchen and hunting knives the same. What varies among these different cutting tools is not edge-angle, it is edge-thickness to provide more or less blade strength as needed for the application. Axes get thicker behind the edge because they need it. But your skinning knife doesn't need to. How many folk claim to sharpen below 30-inclusive but then add a microbevel ~40-inclusive? The edge performs better with that stronger geometry, not worse.

I don't necessarily agree with everything Cliff Stamp says (I think he may, for instance, take steel manufacturing specifications as too closely relevant to knife use), but if someone has made more effort to be rigorous and scientific about edge testing, I sure would like to hear about this unknown person... This isn't exactly a highly complex and hugely competitive "scientific" area where knife-making credentials carry a lot of weight... Probably the contrary, as knife-making likely implies stronger emotions about the subject...

Believe me, I was not happy to hear my $420 Chris Reeves Jereboam (now going for around $1000) in A-2 had much poorer edge holding than some dime store cheapo blade, but if Cliff Stamp says so, I have enough sense to know there is a good chance it is so...

I take my knives down to around 20-25° incusive, and I find this holds up fine in chopping wood: I will do more extensive testing later, but in my opinion a 30° inclusive (15 dps) is only barely acceptable, for no gain at all, except, maybe, a bit of very long-term edge-holding (I'll test that later).

Note I never include any possible microbevel figure, but I try as much as I can to avoid micro bevels when sharpening, since they sometimes kill edge aggression: I like edge aggression above all, because I know useage will make me put a microbevel later anyway...

Any angle over 30° inclusive loses aggression fast with every additional degree. Most factory outdoor edges are at a true 50° to 70°: This is obviously complete nonsense, and people who find this acceptable either have never experienced better edges, or only use very thin-edged folders... My Al Mar "Special Warfare" has a very thin Randall-like 0.4 mm thick edge, and was brand-new at around 50° inclusive: This factory-new performance was utterly miserable... Until, that is, I spent two days to halve this angle...

The testing you quote from Steve Elliot is for wood planer blades that are mostly ground on one side: Even then, the quoted 32° inclusive edge is much sharper than most factory outdoor knife edges are, as delivered... Even taking into account the greater microchipping he observes below 32° inclusive, it is easy to overlook the fact that micro-chipping on a 20° inclusive edge may still retain a lot of edge aggression when using a sawing motion (which the wood chiseling example ignores, because it cannot use a sawing motion)... By comparison, a more open edge angle will result in the edge just getting rounder and rounder: The chips, being smaller, will not have a much taller and sharper surface in between them to maintain aggression when sawing...

Yes in the long run, with no sharpening, the 30° or 40° inclusive edge will be in much better shape, but for all that poor initial use it seems a high price to pay...

Thin edges are of little help if the edge angle is open, and you can see that for yourself by simply cutting a tomato... Most high-end outdoor knives crush or depress the surface of a tomato before slicing through the outer skin, and this has nothing to do with their 1/4" stock: I consider this miserable performance, even if the knife will mostly not be used for that kind of use...

As for chopping wood, I agree this is where thin edges do shine on knives more than edge angle, because in soft wood edge thickness does actually matters more than edge angle. This is why I think the much maligned hollow grind is better for wood chopping knives, because knives below 9" are always weak choppers, and they can hardly bind their hollow grind into wood with a half-inch to an inch bite on a diameter of 5"... On smaller diameter branches, the binding hardly matters... I won't even go into why I think hollow grinds decelerate more gradually, and are thus much more confortable on wood, but I think they are...

Maybe in rough "survival use" a 20° inclusive edge will show a lot of small chips, after days of abuse, where the ridiculous factory edge would still be whole... But if my life depends on it, I'd still rather have the sharper blade between the chips...

Gaston

 

[chiral.grolim]

I take my knives down to around 20-25° incusive, and I find this holds up fine in chopping wood: I will do more extensive testing later, but in my opinion a 30° inclusive (15 dps) is only barely acceptable, for no gain at all, except, maybe, a bit of very long-term edge-holding (I'll test that later).

Again, what thickness??

THICKNESS is what determines edge-strength as well as resistance to cutting, NOT angle. When you reduce your sharpening angle, you reduce the thickness. For penetration into a cutting medium, you need a certain low level of thickness maintained back from the apex to minimize wedging/tugging resistance. That resistance is what gives force to abrasion of the bevel. To minimize abrasion and also tugging (e.g. when shaving or performing surgery), you must minimize thickness. HOWEVER that reduction in thickness impacts the the strength of the edge much more dramatically then it impacts edge-retention, and if you try to cut something which exceeds the threshold (yield point) of your thin blade, be it impact or lateral flex, the blade deforms and fractures/tears more easily and to a far greater extent up the bevel than would have occurred using a slightly thicker geometry. And note well that if the edge folds/compresses because it is too thin, the edge-thickness that results is MUCH thicker than the more durable edge achieved by sharpening at a higher angle, i.e. the thicker angle gives the thinner edge Amazing? Controversial? No, Verhoeven's experiments showed just that thing quite some time ago.

And not only is the thinner angle harder to sustain, it is harder to achieve in the first place due to irregularities in a honing surface and ability to maintain a consistent angle.

The thinnest geometry you can achieve is a "wire edge". How stable/durable is that? What happens when it folds over?

Here is a schematic of a few knives, only one of which is NOT sharpened to 15-dps. Can you tell, just from the schematic of the edges, which cuts with the greatest ease, has the highest edge-retention, and which has the lowest durability?

The utility blade has the lowest apex angle ~15-20 inclusive... and is the least durable blade while also NOT the most efficient cutter. Why is it weak? Too thin at the edge. Why is in not that efficient? Too thick behind the edge

Note I never include any possible microbevel figure, but I try as much as I can to avoid micro bevels when sharpening, since they sometimes kill edge aggression: I like edge aggression above all, because I know useage will make me put a microbevel later anyway...

Any angle over 30° inclusive loses aggression fast with every additional degree. Most factory outdoor edges are at a true 50° to 70°: This is obviously complete nonsense, and people who find this acceptable either have never experienced better edges, or only use very thin-edged folders... My Al Mar "Special Warfare" has a very thin Randall-like 0.4 mm thick edge, and was brand-new at around 50° inclusive: This factory-new performance was utterly miserable... Until, that is, I spent two days to halve this angle...

The testing you quote from Steve Elliot is for wood planer blades that are mostly ground on one side: Even then, the quoted 32° inclusive edge is much sharper than most factory outdoor knife edges are, as delivered... Even taking into account the greater microchipping he observes below 32° inclusive, it is easy to overlook the fact that micro-chipping on a 20° inclusive edge may still retain a lot of edge aggression when using a sawing motion (which the wood chiseling example ignores, because it cannot use a sawing motion)... By comparison, a more open edge angle will result in the edge just getting rounder and rounder: The chips, being smaller, will not have a much taller and sharper surface in between them to maintain aggression when sawing...

Yes in the long run, with no sharpening, the 30° or 40° inclusive edge will be in much better shape, but for all that poor initial use it seems a high price to pay...

Thin edges are of little help if the edge angle is open, and you can see that for yourself by simply cutting a tomato... Most high-end outdoor knives crush or depress the surface of a tomato before slicing through the outer skin, and this has nothing to do with their 1/4" stock: I consider this miserable performance, even if the knife will mostly not be used for that kind of use...

As for chopping wood, I agree this is where thin edges do shine on knives more than edge angle, because in soft wood edge thickness does actually matters more than edge angle. This is why I think the much maligned hollow grind is better for wood chopping knives, because knives below 9" are always weak choppers, and they can hardly bind their hollow grind into wood with a half-inch to an inch bite on a diameter of 5"... On smaller diameter branches, the binding hardly matters... I won't even go into why I think hollow grinds decelerate more gradually, and are thus much more confortable on wood, but I think they are...

Maybe in rough "survival use" a 20° inclusive edge will show a lot of small chips, after days of abuse, where the ridiculous factory edge would still be whole... But if my life depends on it, I'd still rather have the sharper blade between the chips...

The only knives I've received from production companies with angles greater than 40-inclusive were Bussekin, all of which I brought down immediately. My standard are Buck knives all sharpened (in my experience) at 20-dps form the factory and my recent Buck 110 was 0.015" behind that edge. Another recent purchase, the Gerber Order, was 0.020 and 15-dps. We are not discussing spine thickness, just edge-thickness. Both of those knives slice a tomato fine, the Gerber better than the buck, because both were fully sharpened to an apex able to penetrate through the skin and both are thin enough to cause very little wedging as they proceed. Would they slice better if taken thinner? Of course, but I don't use them just for kitchen tasks and i need greater strength elsewhere. The thin AEB-L knife in the schematic above does not get abused the way these other knives do, but they can take MUCH more abuse while still able to perform reasonably well in lighter tasks.

By sharpening at a lower angle without reprofiling the entire blade as described in the OP you gain a) short term increase in cutting performance, b) substantial decrease in edge durability c) minimal increase in edge-retention. If instead you do as described in the OP and reduce the edge thickness you gain a) long term increase in cutting performance, b) no reduction in edge durability, c) long-term increase in edge-retention, as well as benefits like ease of maintenance/resharpening.

Time for some reality: (images taken from scienceofsharp.wordpress.com, ToddS here on the forums)

What is the apex angle in this SEM of a honed razor-blade (note the scale) sharpened at ~15 inclusive? Is it 15 or higher?

Durability: here is the straight razor having cut through a few centimeters of printer paper:

What about a pocket-knife (Spyderco Delica) sharpened to 40-inclusive (normal)?

Here is that pocket-knife after cutting 20 linear feet of double-layered cardboard:

Which blade is more durable, which loses its edge / increase edge-thickness faster? Which has the highest "edge retention"?

 

[Mike157]

Thank you Josh for starting this thread. I love this stuff...I find it very interesting and educational. I checked out your "service" thread. You do some very fine work. I have no doubt that I'll contact you about working on one or more of my blades some day.

Thanks to all others who have contributed to this thread. It is appreciated.

chiral.grolim, some questions concerning your last post if I may....mostly to make sure I understand what's being said: (I apologize if the questions/answers seem too obvious. Sometimes I need to restate things in my own terms for them to stick.)

1) Concerning the utility knife failure and other knives that have what would be considered too thin of an edge. By too thin an edge, you mean too small an edge angle. Yes? The 10 DPS on the utility knife for example.

When you talk about the failure of knives like this, you're saying that the resulting thickness at a failure/tear-out for too thin (shallow edge angle) an edge would be greater than the resulting thickness of a a failure with a comparatively larger edge angle - which implies that the edge stays sharper longer and more easily. Yes?

Staying with the utility blade, I would now guess that reprofiling just the edge bevel to 15 DPS would significantly increase its edge holding/durability quite a bit? Would you still consider the edge thickness (measurement behind the edge where the secondary or edge bevel ends and the primary bevel starts) too thin even for the larger edge angle? If so, what thickness would you prefer to see?

2) Scandi Grinds. I've never actually measured the grind angle, but I'm guessing, for a true zero grind, that they fall somewhere between a "normal" primary grind angle, a bit larger, but substantially less than say a 15 DPS grind that would get way too thick too quickly?

3) Busse. I guess it depends on what model you're talking about, but, and if you don't mind, to what thickness (and angle) are you taking your Busse edges where they give you better performance but are not significantly compromised? I'd love to try (or have Josh) try the same for some of mine.

4) Edge Thickness Measurements. I use a decent set of calipers and a loupe, but don't have a lot of confidence in the precision of my measurements. Any wisdom for taking this type of measurement?

5) Edge Profile Example Recap. It looks like the AEB-L profile would be a great slicer in the kitchen as long as it was treated properly. The Spyderco might be the best all around performer. It looks like it is thinner behind the edge than the utility blade but has the higher edge angle. The Izula, is probably the most stout, but not the cutter/slicer that the other's are. The Izula might be a good smaller all around do everything camp/heavy use knife?

chiral.grolim, if this is too much to deal with, no problem, but it seems you're not adverse to some thorough explanations:thumbup:

Josh, this kind of a large detour, if this is too much, I can delete it. Thanks. Mike

 

[chiral.grolim]

1) Concerning the utility knife failure and other knives that have what would be considered too thin of an edge. By too thin an edge, you mean too small an edge angle. Yes? The 10 DPS on the utility knife for example.

When you talk about the failure of knives like this, you're saying that the resulting thickness at a failure/tear-out for too thin (shallow edge angle) an edge would be greater than the resulting thickness of a a failure with a comparatively larger edge angle - which implies that the edge stays sharper longer and more easily. Yes?

Staying with the utility blade, I would now guess that reprofiling just the edge bevel to 15 DPS would significantly increase its edge holding/durability quite a bit? Would you still consider the edge thickness (measurement behind the edge where the secondary or edge bevel ends and the primary bevel starts) too thin even for the larger edge angle? If so, what thickness would you prefer to see?

:thumbup:
A low angle reduces thickness of the edge at the same distance back from the apex. By reducing thickness, you reduce strength substantially, allowing the edge to deform and then fracture in ways which a slightly thicker edge would not under the same stress due to its higher threshold of strain prior to deformation/fracture. **EDIT** Important note: this only matters IF you achieve that threshold! If you don't, then your edge is sufficiently durable for the task at hand and, as always, thinner cuts better. Don't go making your straightrazors and sushi knives thicker for no reason ** In addition, when the level of stress required to induce fracture in the thicker edge is achieved, the amount of deformation will be far more limited than would be the case for the thinner edge subjected to the same stress as it is WAY above its threshold. Obviously there is a limit to this, namely when durability is at/above the threshold such that increased thickness only detracts from cutting performance.
In the SEMs posted above, note the scale of the images and also the amount of stress applied and then the damage sustained. The edge of the razor, honed at 15-20 inclusive, folds to an apex-width ~4 microns after a few centimeters of paper. The pocket-knife, honed at 40-inclusive, is squashed to an apex width of ~6 microns after 20 feet of doubled cardboard - that's ~500X more cutting through MUCH stiffer material. Neither knife would be suitable for shaving now, but imagine the damage that the razor would have suffered in the cardboard! And the pocket-knife will be easy to restore by grinding away the "cheeks" of squashed material, the razor lost much more bevel-height due to its deformation cutting through much less and less harsh material. The pocket-knife held a narrower apex (i.e. stayed sharper) longer and will be easier to restore.

Regarding resharpening the utility blade to 15-dps, that is exactly what i do after wearing down my edges on them, and I'm happy with it, but most people simply replace the blade. This gives you a stronger edge. If you need a stronger blade then you need something thicker in the primary, and utility blades come is 0.017, 0.025, and even 0.035 stock thickness.

Here is a schematic of edge angles superimposed at the apex and superimposed at the bevel:

2) Scandi Grinds. I've never actually measured the grind angle, but I'm guessing, for a true zero grind, that they fall somewhere between a "normal" primary grind angle, a bit larger, but substantially less than say a 15 DPS grind that would get way too thick too quickly?

I have a Mora "Heavy Duty" (1/8" thick model), the edge-angle is ~14-dps and YES, being a Scandi i.e. low saber and no microbevel, it achieves full thickness VERY fast, sucks at most cutting chores in comparison to knives with a proper 3-5 dps primary bevel and a 15-20 dps microbevel. I also have a Jarvenpaa Aito that is ground to ~9-dps but needs a microbevel due to fragility issues like the utility knife. Because of the thick Scandi design, the blades, while strong back from the edge, are fragile at the apex and begin to wedge very quickly on deeper cuts :thumbdn: Add to that how much material needs to be removed from a scandi-grind in order to maintain that "zero" grind ... I just don't get it.

3) Busse. I guess it depends on what model you're talking about, but, and if you don't mind, to what thickness (and angle) are you taking your Busse edges where they give you better performance but are not significantly compromised? I'd love to try (or have Josh) try the same for some of mine.

There are many here who probably have more experience for a frame of reference, but for me "compromised" is how thin I can take them for the tasks I am putting to them. For "hard use" - may involve lateral prying, impacts with bone or rock or metal - I like them ~0.020 to 0.030" and 15-20 dps to the apex, that is where most of them are at. For general utility, carving, hunting/butchering, down to ~0.012". For lighter-use / slicing performance, down to 0.005 - my only Bussekin this thin is my Scrapmax at ~0.010".

4) Edge Thickness Measurements. I use a decent set of calipers and a loupe, but don't have a lot of confidence in the precision of my measurements. Any wisdom for taking this type of measurement?

Do your best, take multiple measurements at the same position and other positions along the edge. I use a digital micrometer accurate to 0.001", but being off my a few thousandths of an inch doesn't make much difference and honestly will change the next time you sharpen. We aren't working in the submicron scale in our efforts, the SEMs just help to clarify our understanding of reality

5) Edge Profile Example Recap. It looks like the AEB-L profile would be a great slicer in the kitchen as long as it was treated properly. The Spyderco might be the best all around performer. It looks like it is thinner behind the edge than the utility blade but has the higher edge angle. The Izula, is probably the most stout, but not the cutter/slicer that the other's are. The Izula might be a good smaller all around do everything camp/heavy use knife?

:thumbup: I thoroughly agree with your assessments.


And I too apologize if this is to much of a derailment, and also appreciate correction if anything I've posted here is totally wrong.


Also, that is a really nice finish on that Busse, FTR-14c!

 

[Mike157]

chiral.grolim - thanks so much for the excellent response.:thumbup: I don't think anyone, even in college (a number of decades ago), has ever offered more complete and informative answers to my questions. Much appreciated. The graphics with the super imposed apexes and thicknesses is a great visual help (as were the previous graphics and photos). You've helped me develop a more informed way of looking at my blades. And thanks to Josh for starting all of this and including such great information and visuals. Interesting information concerning the scandi grinds, Chiral. Now I have to go take a second look at my Scrapmax. Again, thanks for your time and efforts. Mike

 

[REK Knives]

Cliff stamp is wrong, and numerous users as well as makers have pointed out that going below 30-inclusive can be devastating on steels over a certain hardness and in other than very specific tasks, in other words Cliff's claims are irrelevant.

I normally refrain from posting his stuff here, given the past history, but I would hardly call his claims irrelevant as he does some of the most in depth, and careful, testing that I have seen and double blinds these tests. His video and thread on optimizing your edge for a specific purpose I found to be both helpful and legit. I realized he is either pretty much loved or hated but that aside his work and methods seem to be correct. And may I point out too that, although I don't have references, i have seen where he does not advocate going below 15 dps and .030" thick edges for choppers except for in very specific instances with controlled cuts.

And in step w/ what you pointed out Chiral, here Cliff compares two different blades/steels (vg10 vs s30v) and, to an extent, edge retention goes up as the edge angle decreases. Keep in mind this is just one test and is only slicing hemp, so it is very controlled (so you can't just deduct that a lower edge angle is always better). And he does point out 'At some point the apex will become so weak that it will just fold / collapse due to lack of strength. In order to find the point of optimal edge retention then the apex angle has to be set at the minimum angle which makes it just strong enough to resist deformation so it blunts by slow wear." I think the point is to maximize your blade geometry and edge angle for specific tasks... go as low as possible without causing failure.

Edge "angle" is NOT the most important factor, it is edge thickness that matters most, as angle is merely a description of thickness. Thickness determines edge strength and stability through its cubic relation to stiffness - for every 2x increase in thickness the edge gets 8x stronger! In contrast, a 2x increase in thickness results in only ~4x decrease in cutting efficiency (depending on type of material being cut).

I am glad you bring this point up Chiral... This is why I have made the argument that scandi ground knives have an extremely limited application and most of the time perform poorly compared to more of a conventional grind.

It seems to me that they lack cutting efficiency... which is interesting because many people seem to praise them for cutting efficiency. but they lack cutting efficiency while not being much tougher than a normal blade (ie. one with a primary and secondary bevel). Specifically, I mean toughness at the final/secondary bevel, if they are both at the same final angle (and everything else being equal - blade thickness, width, etc). See the pic below to illustrate... the one inside is conventional (secondary and primary bevel) and the outside thicker one is a scandi. such as this for a real life example.

Axes are sharpened to ~30 inclusive, chipper and chainsaw and chisel and planer blades are all 30-dps or greater, kitchen and hunting knives the same. What varies among these different cutting tools is not edge-angle, it is edge-thickness to provide more or less blade strength as needed for the application. Axes get thicker behind the edge because they need it. But your skinning knife doesn't need to. How many folk claim to sharpen below 30-inclusive but then add a microbevel ~40-inclusive? The edge performs better with that stronger geometry, not worse.

Another great point... which is why it astounds me why so many people are stuck on 20-25dps edges when even felling axes are 15dps! So then... as you point out the trick is to find out how thin you can go without causing edge fracture, blow out, or rippling =) Which is why regrinds need to be task specific and may not be for everyone.

 

[REK Knives]

Which blade is more durable, which loses its edge / increase edge-thickness faster? Which has the highest "edge retention"?

Thanks for posting pics up man... very helpful. I would love to see what would happen cutting the cardboard w/ the straight razor edge with a 25dps micro bevel put on it. Then it would have the strength to resist folding over and maybe even the strength to resist the blunting of the 20 dps edge, all the while being able to cut much better due to the thinner profile.

 

[REK Knives]

Josh, this kind of a large detour, if this is too much, I can delete it. Thanks. Mike

no worries man... i love this stuff as well

On, or off, topic as well (depending on how you look at it)... here is a pic of my Esee Junglas. I did not regrind this but instead back-beveled the edge, as Chiral advocated as a good "compromise" (in this case, this is no compromise at all but actually optimizing the blade for a specific task - chopping wood.) I back-beveled the edge to ~11 dps and then micro beveled at around 20 dps on my wicked edge. I chopped wood (hard, soft, etc) all weekend w/ no issues and with light honing on a diamond rod, still scrape shaving hair. I suffered no edge blow outs or large fracturing and it performed greatly. Keep in mind that this is 1095, not the optimum steel for chopping

 

[Mike157]

Thanks Josh, and great work on the Junglas. Now I have to go eyeball my Junglas too. Mike

 

[sodak]

Here is a schematic of a few knives, only one of which is NOT sharpened to 15-dps. Can you tell, just from the schematic of the edges, which cuts with the greatest ease, has the highest edge-retention, and which has the lowest durability?

Keep in mind that these sorts of results can be varied by using steels that are optimized for thin slicing performance. It all depends on the designed scope of work.

I normally refrain from posting his stuff here, given the past history, but I would hardly call his claims irrelevant as he does some of the most in depth, and careful, testing that I have seen and double blinds these tests.

I agree with you, the problem with him is that he also doesn't hesitate to jump into areas that he is not knowledgeable about without the proper disclaimers. He sometimes has some good tests, but some of his assertions have been debunked by metallurgists here. It would be nice if people would stick to what they know, or at least give the proper disclaimers.

 

[calc]

here is a pic of my Esee Junglas. I did not regrind this but instead back-beveled the edge, as Chiral advocated as a good "compromise" (in this case, this is no compromise at all but actually optimizing the blade for a specific task - chopping wood.) I back-beveled the edge to ~11 dps and then micro beveled at around 20 dps on my wicked edge. I chopped wood (hard, soft, etc) all weekend w/ no issues and with light honing on a diamond rod, still scrape shaving hair. I suffered no edge blow outs or large fracturing and it performed greatly. Keep in mind that this is 1095, not the optimum steel for chopping

Doesn't ESEE/Rowen specifically HT their 1095 for toughness with a slight decrease in edge retention? I wouldn't worry about chopping with it at all, it might not be the Mt. Everest of chopping steels but it's up there, especially when you consider the cost/warranty associated with it. It's been a few years since I've had a larger ESEE knife - right now I'm just down to a 3 and an Izula - but I never had any edge deformation issues, even through very hard wood.

 

[chiral.grolim]

I agree with sodak :thumbup:, and thank you, Josh, for posting another excellent diagram and photos. I have a few more knives waiting to be reprofiled - a newer Buck 301 and PakLite skinner built like axes - that I'll post pics of as soon as they're ready, and this thread is inspiring me to reprofile my Rodent 9 to be like worldwood's chopweiler that he started and Dan Keffeler finished:

I also recently came across GravityRoller's adjustments to a couple of Kershaw camp-knives - still a bit heavy behind the edge but a definite improvement:

[video=youtube;BBQVbxfIeK8]https://www.youtube.com/watch?v=BBQVbxfIeK8[/video]