Pros and cons of Hollow grind?

[FortyTwoBlades]

Personally I absolutely use thickness at different points back in the blade as a consideration when deciding on a grind. Even when designing the knife in the first place. And thickness at different points totally matters when you're talking about different sorts of cuts with different depths to them.

 

[marthinus]

I've always thought in the back of my mind that a hollow grind could be a self jigging knife for sharpening. Though I have never tried it. Picture how a razor is like this.

In theory one can plunk the knife down flat on the stone with the spine riding on one side and the sharpening bevel riding on the other side and just run the knife on the stone until it is apexed. Now a razor gets more complicated (as I understand it I have never sharpened a razor) in that one only uses the stone so far on a razor and stops short of apexing or a bur in any case and then go to the strop for the final edge.

Anybody sharpen their robust hollow ground EDC this way or is this pure fantasy on my part ? ? ? ?

I have for some time. Not as of late.

Here is a thread as example.

https://www.bladeforums.com/threads/cpm-m4-at-low-angles-my-experience-recently.1086828/

 

[marrenmiller]

Personally I absolutely use thickness at different points back in the blade as a consideration when deciding on a grind. Even when designing the knife in the first place. And thickness at different points totally matters when you're talking about different sorts of cuts with different depths to them.

Fair enough. BTW I don't mean people don't make any reference whatsoever to blade thicknesses in their grinds, but only that it seems common to design a blade starting with the bevel height/stock thickness/blank profile and work from there. If I'm going to make a knife, I model it entirely in CAD before doing anything else, just to figure out my plan of attack and handle designs before committing to the work. Maybe you do something differently.

I would love to see someone demonstrate whether a moderate hollow grind (relatively large radius and low concavity, like on a CRK) of a given height/stock width/stick thickness/edge thickness would cut better or worse than a comparable* flat grind.

 

[FortyTwoBlades]

Depends on what you're cutting and at what depth.

As far as design goes, I start with a context of use and let that determine the parameters that make sense. All of the features are to provide benefits. The context of use determines what's beneficial. Then it's a matter of balancing those features in ways that maximize performance features while minimizing sacrifices.

 

[Conner Michaux]

Thanks guys

 

[pinnah]

A full hollow is thinner at all points than a full flat, and a saber hollow of the same height is thinner than a saber flat at all points. I'm talking about equivalent grinds, not a full flat vs saber hollow. Otherwise the comparison would be apples to oranges. Your description of flattening out a hollow grind serves to compare two dissimilar grinds, not equivalent ones.

Ah. Clarity on the terms is helpful.

I am very familiar with the confusion of a full flat grind vs a saber flat grind. Most knife manufacturers I'm aware of use the terms "flat" and "full flat" as equivalent terms but not all do. Buck is a notable exception. When they say "flat" they mean saber flat, not full flat.

I admit to not encountering many people using the term "hollow grind" to mean a full height hollow grind as opposed to what you are referring to as a saber hollow grind. I'm not saying you're wrong. Just noting that I've not encountered that much before and I think this explains our confusion, so there's progress.

Speaking of terms as used by manufacturers in their literature, can you think of any manufacturers who use the term "hollow grind" to refer to a full-height hollow grind? As I go through my mental Rolodex, each and every maker I know uses the term to refer to what you are calling a saber hollow grind. Not challenging you on this. I'm honestly curious to know if there are manufacturers who use the term in that manner. I would find that interesting and helpful.

As for the shoulder of a hollow being sharp: yes, it is more acute of an angle. My question is, does that oppose displacement more than the entire primary bevel of a flat grind, which is thicker the whole time between the edge and the shoulder? I've never seen any wedging like you are describing.

Opposed displacement isn't the entire story with wedging. The other issue is concentrated friction. The sharp shoulder of the modern hollow grind produces friction in ways that a more convexed shoulder does not, which explains why the older Buck grind doesn't bind as much as the modern grind despite using the same thickness stock and very similar grinds otherwise (both saber hollow grinds of similar height). One way you can "see" the concentrated friction is to buy an inexpensive coated (saber) hollow grind fixed blade and use for battoning. You will wear off the coating at the shoulder in very short order and this is happening because this is where the friction is occurring.

 

[pinnah]

Nobody grinds a blade with consideration to thicknesses at given points, but instead as a function of blade stock, blank profile, and bevel height (at least, that's what I do and what it seems most people do when physically making a knife). The theoretical question is: all other blade features being identical, does a hollow grind cut better than a flat grind? Or, if I take a given blade blank and do a comparable height grind with hollow or flat, then which cuts better? That question only makes sense if all other components are identical, and thus comparing with the bevel height is totally fine in this theoretical case.

I'm pretty certain this is not true.

Buck's old semi-hollow grind is interesting and worth studying, IMO. It actually flares out and gets thicker just above the edge to make the edge stronger. Hence the old Al Buck trick of battoning a Buck knife through a bolt on an anvil. Virtuovice (YouTuber) discusses the virtues of low convex vs high convex for bushcraft and deer processing respectively.

Regarding a full height hollow grind, I'm not sure many (any?) makers seek this as a design goal. JackBlack has discussed this off and on over the years in the traditional forum based on his interest in documenting the history of the early Sheffield (England) knife factories. His point (iirc) is that in earlier knife making, the distinction between what we are calling "full flat" and "full height hollow" would have just been chalked up to who was doing the grinding that day. He describes the typical grinding as very large radius grinding stones driven by water power and grinders who laid flat on a platform above the wheels as they worked.

This confusion continues to this day. The Case Sodbuster is often mentioned as an example of a "full height hollow grind" but when I asked the question 4 years ago, some people asserted that a straight edge showed their to be full flat and others slightly hollow. To this day, I don't think Case says which the consider it and it appears that whether a Sodbuster is flat or slightly hollow depends again on who was doing the grinding.

https://www.bladeforums.com/threads/case-large-sodbuster-grind.1235763/

I think an interesting historical question to think about is when the (saber) hollow grind became common. Based on my (modest) collection of vintage Schrades, I would think the roll-over would be in the late 60s. Buck also transitioned away from their early saber flat grinds to hollow (or semi-hollow) grinds. My hunch is that the availability of high speed, small radius grinders combined with crude process automation made the (saber) hollow grind possible during that time period as a mass produced item.

And it is at this point that I can suggest 2 more benefits of the (saber) hollow grind.
1) They look cool. Buck, following the inspiration of Leroy Remer, certainly has used sharply defined and often curving hollow grind shoulders as an aesthetic feature on their knives. Ditto false edges too. The Buck Reaper looks more cool than the full flat and squared spine Buck/Ron Hood Thug. Hood designed a better survival knife but Buck makes a better seller because huge numbers of people buy on looks.

2) Hollow grinds are easier for people with poor sharpening skills to keep sharp. As I understand it, this is one reason why Buck gave up on the semi-hollow grind. People had a hard time sharpening them because the blades were actually pretty thick behind the edge.

 

[Lapedog]

I would like to add that David Boye claims most hollow grinds, unlike his, are ground as the diagram on the left. The blade gets thicker just before the edge because the edge is not where the two convexes of the hollow grind are at their closest, rather it is below it.

You can actually feel it on most hollow ground knives if you pinch the blade on either side in the hollow and drag your fingers downwards past the edge.

 

[miso2]

This confusion continues to this day. The Case Sodbuster is often mentioned as an example of a "full height hollow grind" but when I asked the question 4 years ago, some people asserted that a straight edge showed their to be full flat and others slightly hollow. To this day, I don't think Case says which the consider it and it appears that whether a Sodbuster is flat or slightly hollow depends again on who was doing the grinding.

https://www.bladeforums.com/threads/case-large-sodbuster-grind.1235763/

Interesting.
Thanks for the info.

Mine is quite hollow.

 

[katanas]

Thanks to a number of you, especially FortyTwo's latest posts, I need a drink. I'm sure the posts are quite informative, but they make my head hurt.

 

[marrenmiller]

Ah. Clarity on the terms is helpful.

I am very familiar with the confusion of a full flat grind vs a saber flat grind. Most knife manufacturers I'm aware of use the terms "flat" and "full flat" as equivalent terms but not all do. Buck is a notable exception. When they say "flat" they mean saber flat, not full flat.

I admit to not encountering many people using the term "hollow grind" to mean a full height hollow grind as opposed to what you are referring to as a saber hollow grind. I'm not saying you're wrong. Just noting that I've not encountered that much before and I think this explains our confusion, so there's progress.

Speaking of terms as used by manufacturers in their literature, can you think of any manufacturers who use the term "hollow grind" to refer to a full-height hollow grind? As I go through my mental Rolodex, each and every maker I know uses the term to refer to what you are calling a saber hollow grind. Not challenging you on this. I'm honestly curious to know if there are manufacturers who use the term in that manner. I would find that interesting and helpful.



Opposed displacement isn't the entire story with wedging. The other issue is concentrated friction. The sharp shoulder of the modern hollow grind produces friction in ways that a more convexed shoulder does not, which explains why the older Buck grind doesn't bind as much as the modern grind despite using the same thickness stock and very similar grinds otherwise (both saber hollow grinds of similar height). One way you can "see" the concentrated friction is to buy an inexpensive coated (saber) hollow grind fixed blade and use for battoning. You will wear off the coating at the shoulder in very short order and this is happening because this is where the friction is occurring.

I don't doubt that the friction occurs at the shoulder. However, with an equivalently dimensioned full flat grind, friction would occur over the entire primary bevel. As far as I can tell, the overall displacement of an elastic material from a cutting wedge would be similar for a hollow-ground blade or a flat ground one, provided that the relevant dimensions are the same. This would indicate to me that there's similar normal forces on the blade bevels, and therefore similar friction loads. Unless that shoulder is acute enough to act as a mechanical stop, or it digs into the material, then I can't see why it would cause undue resistance. And those shoulders really are not that much more acute than a flat ground knife.

 

[marrenmiller]

I'm pretty certain this is not true.

Buck's old semi-hollow grind is interesting and worth studying, IMO. It actually flares out and gets thicker just above the edge to make the edge stronger. Hence the old Al Buck trick of battoning a Buck knife through a bolt on an anvil. Virtuovice (YouTuber) discusses the virtues of low convex vs high convex for bushcraft and deer processing respectively.

Regarding a full height hollow grind, I'm not sure many (any?) makers seek this as a design goal. JackBlack has discussed this off and on over the years in the traditional forum based on his interest in documenting the history of the early Sheffield (England) knife factories. His point (iirc) is that in earlier knife making, the distinction between what we are calling "full flat" and "full height hollow" would have just been chalked up to who was doing the grinding that day. He describes the typical grinding as very large radius grinding stones driven by water power and grinders who laid flat on a platform above the wheels as they worked.

This confusion continues to this day. The Case Sodbuster is often mentioned as an example of a "full height hollow grind" but when I asked the question 4 years ago, some people asserted that a straight edge showed their to be full flat and others slightly hollow. To this day, I don't think Case says which the consider it and it appears that whether a Sodbuster is flat or slightly hollow depends again on who was doing the grinding.

https://www.bladeforums.com/threads/case-large-sodbuster-grind.1235763/

I think an interesting historical question to think about is when the (saber) hollow grind became common. Based on my (modest) collection of vintage Schrades, I would think the roll-over would be in the late 60s. Buck also transitioned away from their early saber flat grinds to hollow (or semi-hollow) grinds. My hunch is that the availability of high speed, small radius grinders combined with crude process automation made the (saber) hollow grind possible during that time period as a mass produced item.

And it is at this point that I can suggest 2 more benefits of the (saber) hollow grind.
1) They look cool. Buck, following the inspiration of Leroy Remer, certainly has used sharply defined and often curving hollow grind shoulders as an aesthetic feature on their knives. Ditto false edges too. The Buck Reaper looks more cool than the full flat and squared spine Buck/Ron Hood Thug. Hood designed a better survival knife but Buck makes a better seller because huge numbers of people buy on looks.

2) Hollow grinds are easier for people with poor sharpening skills to keep sharp. As I understand it, this is one reason why Buck gave up on the semi-hollow grind. People had a hard time sharpening them because the blades were actually pretty thick behind the edge.

For the record, I'm not even saying full height hollow grinds are common. I've personally never owned one. Then again, most flat ground knives I own are saber flats, as only Spyderco and traditionals are ones I've owned that were fully flat. Some knives come very close to a "full" hollow, though (Exskelibur, Koenig Arius). For the sake of discussion on which cuts better, that fact doesn't really matter here. Nothing above that shoulder should be doing anything anyway in the context of resisting cutting. I just want to see some evidence of hollow grinds requiring more force to cut with, because I hear that all the time and have never observed it to be true. If all else is held equivalent, which cuts better?

As for the Buck grinds: I've never heard of that before, but my 110 didn't appear to get thicker right at the edge. Nor have any of the other hollow-ground knives I've owned. I'll go check my Recon 1 and see if that's the case. I would think you would notice on a 110, especially when I put a 10 dps edge on it, that all of the sudden the bevel drops away from the edge. Instead, mine behaved like I would expect a hollow to behave (drawing on the right above from Lapedog). I would think that the grind being thinner above the edge is a result of sloppy production and grinding rather than being intentional.

I might just grind a couple test blanks out and see which ones take more force to displace cutting mediums on a scale.

 

[GatorFlash1]

Although I EDC a hollow grind Spyderco Gayle Bradley 1, I have a CRKT Hi Jinx which is an awesome great hollow grind, knife of the year by Blade Magazine. If you are a fan of hollow grinds check out these videos of two great knives. What do you think of these grinds?

 

[pinnah]

I don't doubt that the friction occurs at the shoulder. However, with an equivalently dimensioned full flat grind, friction would occur over the entire primary bevel. As far as I can tell, the overall displacement of an elastic material from a cutting wedge would be similar for a hollow-ground blade or a flat ground one, provided that the relevant dimensions are the same. This would indicate to me that there's similar normal forces on the blade bevels, and therefore similar friction loads. Unless that shoulder is acute enough to act as a mechanical stop, or it digs into the material, then I can't see why it would cause undue resistance. And those shoulders really are not that much more acute than a flat ground knife.

Hey Marley,

I don't think the issue is friction strictly defined. It is more about a mechanical force of resistance.

Two thought experiments to illustrate the point. First, consider a hiker attempting to walk in waist deep snow. Two things to note. First, the weight of the hiker is concentrated on a small area of their boot sole and as a result, they "post hole", or sink up to their waist. Second, because their legs are deep in the snow, they encounter the strong resistance force of the snow against the front of their legs. In contrast, consider the XC skier traveling on the same snow with suitably long and wide skis. Due to the large surface area of the skis, the weight of the skier is distributed across a greater surface area and as a result, the skier only sinks into the snow a matter of a few inches. And because the skier is only a few inches down in the snow, they experience no meaningful resistance to their forward movement.

Second analogy... Imagine dragging your finger tip across loose sand. Now trace the same arc in the sand by pushing your finger in to increasing depths. The deeper you push your finger into the sand, the more frontal area you have and the greater mechanical resistance to forward movement.

The same thing is happening on hollow grind and the problem is worse the tighter the radius is as is approaches the shoulder. The shoulder localizes and concentrates the force of the knife against the medium being cut, just like hiking boots concentrate the force of the hiker pressing on the snow. The should is thus pushed down into the medium locally (as much as the medium can deflect) and this creates mechanical drag.

Another way to think about it is that the sharp should is like a flap on an airplane wing.

Hope this helps.

 

[pinnah]

For the sake of discussion on which cuts better, that fact doesn't really matter here. Nothing above that shoulder should be doing anything anyway in the context of resisting cutting. I just want to see some evidence of hollow grinds requiring more force to cut with, because I hear that all the time and have never observed it to be true. If all else is held equivalent, which cuts better?

Hey Marley,

You are right to point out that on a (saber) hollow grind, the flat above the shoulder isn't doing anything. This is particularly true with stiff, difficult to separate materials like potatoes.

But don't forget that the power needed to drive a wedge through a hard material increases with the effective angle of the wedge. That is, if you take 2 wedges of equal width but different heights (from apex to spine), the shorter one a) will create a larger overall wedging angle and b) will take more force to drive through the material.

Given 2 blade blanks of equal width and equal height (apex to spine), a (saber) hollow grind will act as a shorter wedge with a larger wedging angle.

As for the Buck grinds: I've never heard of that before, but my 110 didn't appear to get thicker right at the edge. Nor have any of the other hollow-ground knives I've owned. I'll go check my Recon 1 and see if that's the case. I would think you would notice on a 110, especially when I put a 10 dps edge on it, that all of the sudden the bevel drops away from the edge. Instead, mine behaved like I would expect a hollow to behave (drawing on the right above from Lapedog). I would think that the grind being thinner above the edge is a result of sloppy production and grinding rather than being intentional.

I might just grind a couple test blanks out and see which ones take more force to displace cutting mediums on a scale.

Lapedog's pictures are perfect. I think Boye is incorrect though and I think most hollow grinds are like the picture on the right, not on the left. Modern Bucks are like the picture on the right. If you want to see a semi-hollow grind (like Lapedog's left most picture), you will need to find Buck hunting knives from the 70s or 60s. Here is a mid-70s vintage "2 dot" 110.
Buck 110 by Pinnah, on Flickr

Please observe the glare lines along the very near the blade tang. Between the glare in the deep recess of the hollow and the glare of the edge bevel, you will the satin finish where the blade thickens up before dropping to the bevel.

My understanding is that Buck used to do this prevent against edge breaking. Al Buck was known to demonstrate the strength of his fixed blades at fairs by hammering the knife through steel bolts - hence the Buck anvil logo.

As an interesting side-effect, that older 110 throws feathers and curls on wood shavings like a nicely convexed Mora. Much better at making shavings than current Bucks, which are ground like Lapedog's right most picture. Buck calls it their "Edge 2000" profile and it does better on CARTA tests (it's thinner behind the edge), is easier to sharpen, and (I think) is better at cutting meat (as hollow grinds do).

 

[marrenmiller]

Hey Marley,

You are right to point out that on a (saber) hollow grind, the flat above the shoulder isn't doing anything. This is particularly true with stiff, difficult to separate materials like potatoes.

But don't forget that the power needed to drive a wedge through a hard material increases with the effective angle of the wedge. That is, if you take 2 wedges of equal width but different heights (from apex to spine), the shorter one a) will create a larger overall wedging angle and b) will take more force to drive through the material.

Given 2 blade blanks of equal width and equal height (apex to spine), a (saber) hollow grind will act as a shorter wedge with a larger wedging angle.



Lapedog's pictures are perfect. I think Boye is incorrect though and I think most hollow grinds are like the picture on the right, not on the left. Modern Bucks are like the picture on the right. If you want to see a semi-hollow grind (like Lapedog's left most picture), you will need to find Buck hunting knives from the 70s or 60s. Here is a mid-70s vintage "2 dot" 110.
Buck 110 by Pinnah, on Flickr

Please observe the glare lines along the very near the blade tang. Between the glare in the deep recess of the hollow and the glare of the edge bevel, you will the satin finish where the blade thickens up before dropping to the bevel.

My understanding is that Buck used to do this prevent against edge breaking. Al Buck was known to demonstrate the strength of his fixed blades at fairs by hammering the knife through steel bolts - hence the Buck anvil logo.

As an interesting side-effect, that older 110 throws feathers and curls on wood shavings like a nicely convexed Mora. Much better at making shavings than current Bucks, which are ground like Lapedog's right most picture. Buck calls it their "Edge 2000" profile and it does better on CARTA tests (it's thinner behind the edge), is easier to sharpen, and (I think) is better at cutting meat (as hollow grinds do).

Wow, you're right, that's very obvious. I think most hollow grinds are not like that, but this one clearly appears to thicken before the edge.

For the wedging effect, I don't agree that a hollow acts as a greater wedge. The wedge dimensions are from tip to shoulder, so it should be identical to a comparable flat grind with the same height to shoulder. Material would deflect the same way and would come off the sides of the grind at a comparable angle. Stiff materials do not need to follow the concave surface of a hollow grind when displaced, and might only contact at the edge bevel and at the shoulder. I would agree that the rate that displacement force develops increases faster than with a flat grind as you move up the bevel, but I don't think the displacement force would increase above that of a comparable flat at a given height up the bevel. That might make it feel to a person as though it requires more force to cut with, but I think a careful measurement would likely disabuse such notions.

Otherwise, maybe I'm not understanding what you're trying to say about comparable grinds.

 

[marrenmiller]

Hey Marley,

I don't think the issue is friction strictly defined. It is more about a mechanical force of resistance.

Two thought experiments to illustrate the point. First, consider a hiker attempting to walk in waist deep snow. Two things to note. First, the weight of the hiker is concentrated on a small area of their boot sole and as a result, they "post hole", or sink up to their waist. Second, because their legs are deep in the snow, they encounter the strong resistance force of the snow against the front of their legs. In contrast, consider the XC skier traveling on the same snow with suitably long and wide skis. Due to the large surface area of the skis, the weight of the skier is distributed across a greater surface area and as a result, the skier only sinks into the snow a matter of a few inches. And because the skier is only a few inches down in the snow, they experience no meaningful resistance to their forward movement.

Second analogy... Imagine dragging your finger tip across loose sand. Now trace the same arc in the sand by pushing your finger in to increasing depths. The deeper you push your finger into the sand, the more frontal area you have and the greater mechanical resistance to forward movement.

The same thing is happening on hollow grind and the problem is worse the tighter the radius is as is approaches the shoulder. The shoulder localizes and concentrates the force of the knife against the medium being cut, just like hiking boots concentrate the force of the hiker pressing on the snow. The should is thus pushed down into the medium locally (as much as the medium can deflect) and this creates mechanical drag.

Another way to think about it is that the sharp should is like a flap on an airplane wing.

Hope this helps.

I'm sorry, but I simply don't buy that. The difference in angle at that shoulder is a few degrees, at best. I understand the point you're trying to make but I think you're vastly overstating any potential effect that a slightly sharper shoulder could have. It's not like a mechanical lock develops all of the sudden once you pass a few degrees in shoulder angle. If anything, any slight affects as such are likely encountered by both sorts of grinds. I could see that, given a tiny grinding radius and a deep hollow grind, that might start to outweigh benefits of the hollow grind, but most production knives seem to be ground with a fairly large wheel.

As for frontal area example, they are the same for the different grinds. It's not like sticking your finger in further, but closer to sticking it in wider but shallower, or deeper but narrower.

Again, you need to weigh the localized force at the shoulder and any tiny increase in mechanical lock, if any, against a stiff material applying a more distributed load against the primary bevel on a flat grind, and possibly greater local displacement of material at that primary bevel, where there is no displacement or less displacement on a hollow grind. After all, it's not like that flat grind just gives you strength for free with no consequences.

 

[Lapedog]

For the record, I'm not even saying full height hollow grinds are common. I've personally never owned one. Then again, most flat ground knives I own are saber flats, as only Spyderco and traditionals are ones I've owned that were fully flat. Some knives come very close to a "full" hollow, though (Exskelibur, Koenig Arius). For the sake of discussion on which cuts better, that fact doesn't really matter here. Nothing above that shoulder should be doing anything anyway in the context of resisting cutting. I just want to see some evidence of hollow grinds requiring more force to cut with, because I hear that all the time and have never observed it to be true. If all else is held equivalent, which cuts better?

As for the Buck grinds: I've never heard of that before, but my 110 didn't appear to get thicker right at the edge. Nor have any of the other hollow-ground knives I've owned. I'll go check my Recon 1 and see if that's the case. I would think you would notice on a 110, especially when I put a 10 dps edge on it, that all of the sudden the bevel drops away from the edge. Instead, mine behaved like I would expect a hollow to behave (drawing on the right above from Lapedog). I would think that the grind being thinner above the edge is a result of sloppy production and grinding rather than being intentional.

I might just grind a couple test blanks out and see which ones take more force to displace cutting mediums on a scale.

No it’s not a sloppy production error. It is by design so that way once the material “jumps” over the thicker edge it is no longer in contact with the sides of the blade. The David Boye hollow grind will have the material always be in contact.

You can test it yourself. Pinch the blade on either side and pull your fingers down past the edge until the blade slips out of your pinched fingers. You will feel that little “speed bump” yiur fingers go over right before they pass over thr edge. So basically you are pinching in the hollows on either side of the blade and slowly pulling your knife upwards out of the pinch.

 

[pinnah]

No it’s not a sloppy production error. It is by design so that way once the material “jumps” over the thicker edge it is no longer in contact with the sides of the blade. The David Boye hollow grind will have the material always be in contact.

You can test it yourself. Pinch the blade on either side and pull your fingers down past the edge until the blade slips out of your pinched fingers. You will feel that little “speed bump” yiur fingers go over right before they pass over thr edge. So basically you are pinching in the hollows on either side of the blade and slowly pulling your knife upwards out of the pinch.

Lapedog, can you name some brands (other than old bucks) that have this thickening above the edge?

 

[Lapedog]

Lapedog, can you name some brands (other than old bucks) that have this thickening above the edge?

My CRKs do. Virtually every hollow ground knife I’ve tested does.