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Hollow Grind vs. Flat Grind...
- Thread starter sturluson
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What I was getting at is this: what's the difference in performance between the hollow grind and the flat grind? Many people seem to prefer the flat grind, but why? And is the flat grind harder to produce than the hollow grind?
I've seen bits and pieces of these questions addressed in other threads, but never all in one place.
How about it, Sebenzaholics?
I've seen bits and pieces of these questions addressed in other threads, but never all in one place.
How about it, Sebenzaholics?
I have both hollow and flat ground Sebenzas and my preference is for the flat ground blade. First, it gives the knives a nice heft and improves the balance. Second, and more importantly the blade profile improves cutting IMHO as the spine doesn't get stuck on deeper cuts as it does on the hollow-grounds.
Don't get me wrong, both are great working knives but the flat ground has the edge over the regular style.
Don't get me wrong, both are great working knives but the flat ground has the edge over the regular style.
I read an article a ways back that interviewed butchers as to their preferences in knife grinds. The flat grind was preferred over the hollow grind among those interviewed for the article for its cutting performance.
In the new issue of Blade Magazine, there is an article on the knives of Dan Farr used in cutting contests. The use of flat or convex grinds are considered the appropriate blade design for a competitive knife. Interestingly, a profiled blade spine is also considered important in reducing friction in certain cuts, as well as a convex edge grind. Both of these are features of all Sebenzas.
My opinion is that edge grind and geometry are more important for cutting performance than primary bevel, for most small cutting tasks. For larger and longer cutting chores, the parasitic drag on the cut material favors the flat grind over the hollow grind. This is what the butchers said, and they should know!
The flat grind should also be advantageous in chopping, as it provides more mass behind the edge. The additional weight of a large, flat ground blade could be mitigated with a distal taper.
Over many years of use and sharpening, a flat grind becomes more and more difficult to maintain because it continues to get thicker as the blade edge is reprofiled. This is one advantage of the hollow grind.
Finally, there is a certain aesthetic beauty to a nicely polished and hand ground hollow grind, and an appreciation for the high level of skill necessary to apply it symmetrically to the blade. This is something I truly appreciate and value in the knives of CRK.
I don't know if it is more difficult or not to handgrind[[/I] a flat grind vs. hollow grind to a blade. The Sebenza flat grinds were CNC'd and not hand ground. The problem that Chris had was getting an acceptable yield of CNC flat ground blades that met his quality standards.
My opinion is that for most cutting chores for which you would use a small knife, there is no significant performance difference between a flat grind and a hollow grind. But choice is always good! By the way, my flat grind Sebbies are not for sale!
In the new issue of Blade Magazine, there is an article on the knives of Dan Farr used in cutting contests. The use of flat or convex grinds are considered the appropriate blade design for a competitive knife. Interestingly, a profiled blade spine is also considered important in reducing friction in certain cuts, as well as a convex edge grind. Both of these are features of all Sebenzas.
My opinion is that edge grind and geometry are more important for cutting performance than primary bevel, for most small cutting tasks. For larger and longer cutting chores, the parasitic drag on the cut material favors the flat grind over the hollow grind. This is what the butchers said, and they should know!
The flat grind should also be advantageous in chopping, as it provides more mass behind the edge. The additional weight of a large, flat ground blade could be mitigated with a distal taper.
Over many years of use and sharpening, a flat grind becomes more and more difficult to maintain because it continues to get thicker as the blade edge is reprofiled. This is one advantage of the hollow grind.
Finally, there is a certain aesthetic beauty to a nicely polished and hand ground hollow grind, and an appreciation for the high level of skill necessary to apply it symmetrically to the blade. This is something I truly appreciate and value in the knives of CRK.
I don't know if it is more difficult or not to handgrind[[/I] a flat grind vs. hollow grind to a blade. The Sebenza flat grinds were CNC'd and not hand ground. The problem that Chris had was getting an acceptable yield of CNC flat ground blades that met his quality standards.
My opinion is that for most cutting chores for which you would use a small knife, there is no significant performance difference between a flat grind and a hollow grind. But choice is always good! By the way, my flat grind Sebbies are not for sale!
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jki,
NIce writeup on hollow versus flat grinds. I didn't realize that CRK was using CNC for putting the flat ground edges on the limited run of knives. I had always thought that he and his staff were having difficulty getting the edge quality they wanted, but done by hand. I guess I was wrong. Anyway, getting back to hollow versus flat grind, I do believe it is more difficult for a custom maker to put a flat grind on than that of a hollow grind. I have a few of Bob Dozier's knives. He primarily uses a hollow grind on his knives, but will put a flat or convex grind on a knife if requested, but he charges quite a premium for doing so. Pretty much all of your run of the mill kitchen cutlery use a flat grind, but since the grind is done by machine, costs are kept low.
I have a flat grind Sebenza, but have not used it as yet since I have so many other knives, but have been considering putting it to use. I have a Spyderco Sharpmaker. Can anyone tell me if there is any differences to consider in using the Sharpmaker with a flat grind versus the hollow grind blade?
NIce writeup on hollow versus flat grinds. I didn't realize that CRK was using CNC for putting the flat ground edges on the limited run of knives. I had always thought that he and his staff were having difficulty getting the edge quality they wanted, but done by hand. I guess I was wrong. Anyway, getting back to hollow versus flat grind, I do believe it is more difficult for a custom maker to put a flat grind on than that of a hollow grind. I have a few of Bob Dozier's knives. He primarily uses a hollow grind on his knives, but will put a flat or convex grind on a knife if requested, but he charges quite a premium for doing so. Pretty much all of your run of the mill kitchen cutlery use a flat grind, but since the grind is done by machine, costs are kept low.
I have a flat grind Sebenza, but have not used it as yet since I have so many other knives, but have been considering putting it to use. I have a Spyderco Sharpmaker. Can anyone tell me if there is any differences to consider in using the Sharpmaker with a flat grind versus the hollow grind blade?
Just a little more information on the CRK flat grinds. The actual blade grinding was done by an outside vendor. Chris was intimately involved in the tooling design and working closely with the vendor to get the production process set up. Apparently, despite the large effort expended on the project, the yield was just not sufficient to justify continuing into production, and the production was cancelled. I guess when your in-house machining tolerances are held to half a ten-thousandths, then everyone else's work just can't measure up. Kudos to Chris and CRK for failing to compromise on quality!
I had some further thoughts on the flat grind vs. hollow grind performance comparison. As a flat grind cuts into a material, the flat grind profile tends to cleave apart the material as it rides up the blade away from the edge. This cleaving helps to part the cut and improve the cutting efficiency. Though much less frequently encountered, the convex blade profile may be even better in this regard.
A hollow grind, however, allows the material to ride back along the hollow bevel, increasing friction (even moreso as it encounters the curvature of the grind) without the benefit of parting the material to aid in cutting efficiency.
Just my guess...
I had some further thoughts on the flat grind vs. hollow grind performance comparison. As a flat grind cuts into a material, the flat grind profile tends to cleave apart the material as it rides up the blade away from the edge. This cleaving helps to part the cut and improve the cutting efficiency. Though much less frequently encountered, the convex blade profile may be even better in this regard.
A hollow grind, however, allows the material to ride back along the hollow bevel, increasing friction (even moreso as it encounters the curvature of the grind) without the benefit of parting the material to aid in cutting efficiency.
Just my guess...
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jki,
Thanks for the followup information. I hope the 130 or so flat grind Sebenza's that were sold by CRK did meet his usual standard of excellence. Let me modify the above statement with, I'm sure that that the flat grind Sebenza's sold by CRK met his high standards.
I suppose that unless the material being cut is thick, thick enough to approach the spine of the blade, you wouldn't notice much difference between hollow cut and flat grind. I agree that the flat grind does seem to give the blade a little more strength even though most of us don't use our Sebenza's as a prybar, however I think the hollow grind acquires the sharpest edge due to less edge material, but also rolls the easiest in my opinion. Regardless, I'm a fan of both designs. I've also heard that the convex blade grind is the best of both worlds, but it is also the more difficult to sharpen for the average knife owner. You really need a belt grinder and a good strop to maintain the convex edge.
Thanks for the followup information. I hope the 130 or so flat grind Sebenza's that were sold by CRK did meet his usual standard of excellence. Let me modify the above statement with, I'm sure that that the flat grind Sebenza's sold by CRK met his high standards.
I suppose that unless the material being cut is thick, thick enough to approach the spine of the blade, you wouldn't notice much difference between hollow cut and flat grind. I agree that the flat grind does seem to give the blade a little more strength even though most of us don't use our Sebenza's as a prybar, however I think the hollow grind acquires the sharpest edge due to less edge material, but also rolls the easiest in my opinion. Regardless, I'm a fan of both designs. I've also heard that the convex blade grind is the best of both worlds, but it is also the more difficult to sharpen for the average knife owner. You really need a belt grinder and a good strop to maintain the convex edge.
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Figure also butchers use knives that are half as thin as the conventional Sebenza. Look at any of your normal kitchen knives and you will see that they are all flat ground due to the thickness(or should I say thinness).jki said:
On EDC folding knives the edge angle is the key, without the proper angle and heat treatment it won't cut, no matter what the grind.
I don't think many people using a large Sebenza can really tell the difference in cutting ability from flat to hollow. I have, and used both flat and hollow ground Sebs for field dressing whitetail deer and I couldn't tell any difference in cutting performance, even when skinning. I only perfer the looks and haft of the flat ground Sebenza blade. That, and all that were made were BG-42 steel.
Here is a piece of trivia regarding flat ground Sebenzas.
This is from an email I wrote Anne in 2004 inquiring about the possible availability of flat ground Sebenzas:
I am sorry to have to tell you that we don't have any flat ground blades
any longer. The last Large Flat Ground Sebenzas that we made were sold
from here in June 2003.
Anne
This is from an email I wrote Anne in 2004 inquiring about the possible availability of flat ground Sebenzas:
I am sorry to have to tell you that we don't have any flat ground blades
any longer. The last Large Flat Ground Sebenzas that we made were sold
from here in June 2003.
Anne
Not related to the Sebenza, I have small and large both hollow, but in general probably there is only small noticable diff between flat vs. hollow in chopping DRY wood, in fact in dry wood hollow tends to give greater penetration without binding problem more common in wet wood. Most axes are hollow ground behind convex edge bevel after all- the hollow grind can helps to " spit out" the wood chips to the side instead of flying straight back into user.
With the Benchmade RSK MK1 (Ritter Grip) being a flat-ground knife with a blade obviously designed with some Sebenza-esc influence by a man with a lot of respect for Chris Reeve and and his fine knives not to mention the same blade material and very similar blade size and geometry, I thought I would compare it to my Large regular Sebenza. I found that in deep cuts on things like vegetables and cardboard the Ritter grip was a better cutter for me and the difference was quite noticable. For shallower cuts there was no difference. There were no situations where the Sebenza was better slicer although there are certainly plenty of reasons why the Sebenza is still IMHO a better knife overall (at least for my uses). It is important to note also that not only is the blade on the Ritter Grip a flat ground blade but it is also thinner [0.115 in. (2.92 mm)] than the blade on the large regular Sebenza.
Having made this comparison I too would really like to own a flat ground Sebbie, although I would like mine in S30V so I know it will never happen.
Even so, if I would still like to keep it at the stock 0.125" (3.175mm) thickness rather than the thinner 0.115 in. (2.92 mm) thickness used on the Ritter Grip. Afterall the Sebenza's "built-like-a-tank" construction is a big part of why I would still have to say it is the better knife overall even though it doesn't slice the deep cuts quite as well as it probably would with a flat grind.
Having made this comparison I too would really like to own a flat ground Sebbie, although I would like mine in S30V so I know it will never happen.
Even so, if I would still like to keep it at the stock 0.125" (3.175mm) thickness rather than the thinner 0.115 in. (2.92 mm) thickness used on the Ritter Grip. Afterall the Sebenza's "built-like-a-tank" construction is a big part of why I would still have to say it is the better knife overall even though it doesn't slice the deep cuts quite as well as it probably would with a flat grind.I own both a large flatground Sebenza and a first production run Rittergrip.
Out of the box the Sebbie was sharper, but the cutting edge profile of the RSK was thinner, so it went through deep cuts with less effort.
After two or three years of constant use (these two knives are the most used EDC's in my 50 knife collection), they both have broken in to cut about the same.
I reprofiled the cutting angle on the Sebbie on a Sharpmaker to make it thinner, and now it keeps up with RSK on the thicker stuff. The bigger difference in "feel" and heft comes from the weight of the handles, and the solidness of the lock-up.
I find the Sebenza is far easier to maintain, and the framelock is simpler and more robust than the Axis lock.
For comparative research purposes I went and bought a regular hollowground S30V Sebbie for a control....
George
Out of the box the Sebbie was sharper, but the cutting edge profile of the RSK was thinner, so it went through deep cuts with less effort.
After two or three years of constant use (these two knives are the most used EDC's in my 50 knife collection), they both have broken in to cut about the same.
I reprofiled the cutting angle on the Sebbie on a Sharpmaker to make it thinner, and now it keeps up with RSK on the thicker stuff. The bigger difference in "feel" and heft comes from the weight of the handles, and the solidness of the lock-up.
I find the Sebenza is far easier to maintain, and the framelock is simpler and more robust than the Axis lock.
For comparative research purposes I went and bought a regular hollowground S30V Sebbie for a control....
George
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Most of the material I've read says flat grinding is much harder to do than hollow. I've always flat ground my blades, so I guess I don't notice. For me, hollow grinding would be the hardest, since I don't know how.
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jki said:
At the risk of taking this thread off on a tangent, I also read that article about competition blades, and I thought the comments about hollow grinds were more geared towards dynamic balance. They were talking about hollow grinding the blade to be very light, and using a big pommel to bring the balance point back to the guard. This wasn't the fault of the hollow grind in itself; just that their idea of balance didn't work. (which I could have told them, had they asked.
) By the way, I'm not trying to dispute the notion that hollow and flat grinds perform differently in deep cutting; just that I don't think that's what the article was referring to. Also, the balance is created by the way mass is distributed through the blade and handle. It's certainly possible to make knives with the same dynamic balance using any of the three grind types, though the finished knives will look different.