Flat Grind vs. Hollow Grind

K

Kysa

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I prefer the blades of the DragonFly, Military, and Calypso-Micarta over most (not all) hollow ground blades. I find flat grinds elegant, while there is the traditional beauty of a hollow ground blade.

But what exactly is the 'function' or purpose of each?
 
Kysa,
I am really into the flat grind myself. To me it is the more traditional grind, looking at historic blades. Well made versions of both types should cut just about anything, but most people (IMO) would say that the hollow grind it more for cutting flesh (though there are obviously lots of people using hollow ground blades to do other things-including myself). I just like the flat grind for utility work because it offers less resistance in cutting cardboard or heavy line. I also like a flat grind for cutting wood. These are the things that I find I cut most often. I don't mind a hollow ground blade if it is done on a big wheel to make it a shallow hollow grind.

One of the best cutting blades that I own is a Boye Basic 3 sheath knife. Though the integral handle is less than ideal for long term use that baby will cut and cut and cut. I attribute this to the dendritic steel and the flat grind. I don't know if this answers your question or not. There are numerous articles (cyber and paper) about the virtues of all grind types. I think the May Blade even has an article re: this.
 
The flat grind is supposed to be sharper, since the blade overall is typically thinner, so there is less drag on the material being cut. Hollow grinds, on the other hand, put more metal behind the edge, giving it more strength. Of course, there are gross generalizations, since it depends on the height of the grinds, thickness of the blade, etc
 
I prefer flat grinds as well. They have good "aerodynamics" when cutting through materials. Each of my flat ground Spyders - Calypso, Calypso Jr, Featherweight, G-10 Police, and Military - are all aggressive and fast. And flat grinds are also great looking as well.

------------------
Dexter Ewing
Knife Reviews Moderator

"The keystroke is mightier than the sword"

 
Well done hollow grinds like on a Sebenza are very good at shallow cutting as the edges are very thin, thinner than a flat grind with the same stock used.

The performance of the hollow grind starts to suffer and favors a flat grind when you need to make deep cuts where the whole blade gets pushed into the material. Its hard to do that type of cutting with a deep hollow grind as the faces near the spine are almost perpendicular to the material being cut.

-Cliff
 
Right! Kysa, you can check out the Blade Geometry FAQ to find out more.

The hollow grinds that flare out thick at the bottom -- like on a typical Buck -- I don't find particularly excel at anything. They have the non-linear expansion of a hollow-ground knife that disrupts deep cutting, but they lose the edge-thinness advantage of the type of hollow grind I'll describe below.

If you don't flare the ends out, you get a hollow grind like the Sebenza. Here the edge ends up very thin, and we should all know by now thin edges cut VERY well. This gives a performance advantage for shallow cutting. Of course, this type of thin edge will also be more susceptible to rolling or chipping. As Cliff pointed out, the hollow grind doesn't do well for deep cutting. The non-linear expansion of the grind as you get nearer the spine tends to wedge and cut inefficiently. So this type of hollow grind is good for optimum shallow cutting performance where edge strength is not the top concern.

The full flat grind (from spine to edge) also has a thin edge, but not quite as thin as the hollow grind. For shallow cuts, it will not cut quite as well, but will be stronger. For deeper cuts, the flat grind really excels. There's a reason why kitchen knives are usually a full flat grind -- this grind really works for deep cuts of all kinds. So the flat grind loses a little shallow-cutting performance, but gains strength and deep-cutting performance.

A sabre grind, which is a flat grind that starts from the middle of the blade instead of the spine, gains even more in strength, but suffers in cutting performance for both deep and shallow cuts.

I've completely ignored niche jobs like splitting, where you want a rapid increase in width to split (say) kindling.

Joe
jat@cup.hp.com
 
And here I always thought kitchen knives were flat ground just because that was the cheapest and quickest way to make them...
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O_D
 
When Kysa first posted the question, my thought was, "I'm the moderator but I know that there are a number of forumites that could really explain this one well, especially Joe. I'll wait a couple of days and see". Thanx much. You make it easy to moderate.
sal
 
Now, Sal, I can't get you off that easily. What is YOUR personal preference? Spyderco is schizo regarding this issue. Flat ground Military and hollow ground Police (two of your children); flat ground Calypso/Jr. and hollow ground Endura/Delica. (Then you're talking about flat ground Police coming out, and A.G. Russel sells special flat ground Jess Horns.) What is the rational behind this phenomenon? Is there a philosophical paradigm shift happening?

slowjocrow
 
Slowjocrow - As a knife designer (albeit specialty knives), It is my obligation to design knives that the ELU can appreciate and enjoy. The flat ground vs hollow ground arguments have been around longer than Spyderco and will continue for some time. And for all of the reasons that Joe mentioned. The "general" public seems to prefer hollow ground blades. Probably more because of the appearance than the peformance. Modern machinery and modern skills can make some pretty sexy grind lines. These are absent in the flat ground blade, unless a swedge is added.

The same is true of plain edges vs serrated edges. This argument is going to continue for some time as well. Especially with the development of newer and more efficient serrations and steels.

From the performance standpoint overall, my personal preference is for the flat ground from the edge to spine. No visible grind lines, no swedge if strength is a factor, like the Military, or a small swedge where heavy duty is not a major factor, such as in the Dragonfly, Calypso & Jr. An exception is the Rescue/Mariner models. These I feel will be used for prying and a hollow grind allows me to keep the spine at full thickness all the way out to the tip. Pretty hard to bread a tip on a Spyderco Rescue.

Hollow ground blades will generally sharpen faster, and not have to be "thinned out" as soon as a flat ground blade.

From my personal point of view, I will not sacrifice performance for appearance. But that is why we have Custom Knifemakers designing many of our knives. Bob "T's" Starmate would not be as dynamic in appearance if it were flat ground. With 440V, you have a strong, highperformance design that is also pleasing to the eye.

Sorry for the rant and the sales pitch.
sal
 
Don't apologize Sal. It would appear that the folks around here are BEGGIN' for your rants and sales pitches. It sounds like flat and plain is the most vocal choice on the forums but I know that people that don't sharpen knives or use them a whole lot like serations. I gave a roommate who is a rock climber an old serrated Delica I had and I don't think that he has stopped carrying it one day. He uses it all the time and it is still pretty sharp (I did touch it up a couple of times for him). Nylon kernmantle rope is pretty tough, and the Spectraline (specterline?) is supposed to be even tougher. Pretty good case for serations in my book.
 
*Sound of a dead horse being beaten*

Hey, have a quick question:

Why is the micarta Calypso Jr. flat-ground and the stainless hollow ground? Is it a weight-saving thing, or a space-saving thing, or just a way to offer both hollow and flat ground blades?

PREDICTION: Marketing told Sal that knife-nuts like micarta and flat blades, and that non-knife-nuts like stainless and hollow ground, so rather than have 4 SKUs he opted for 2.

Mike
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[This message has been edited by Coronach (edited 13 April 1999).]
 
I'll throw in my negative two bits here. I prefer the performance of the hollow ground in a folder since it gives me a better edge profile for the not so wide folder blade. I like the looks of the hollow ground blades better, but looks aren't important. I consider 1/8 inch thick hollow ground blades weaker at the edge since there is a dip in the metal before you get to the edge in most knives. Of course I like the modified flat grind with a little slab on the blade before the grind starts, like the saber grind but not starting so far down.
 
Mike - Never knowing what the ELU will like for sure, I designed the flat ground Micarta for me and the stainless hollow ground for everyone else. We also felt that is would be a good test as you suggest. Truthfully, the results of sales surprized me.
sal
 
As I have stated before I tend to like a flat ground blade for general utility use. It seems that the Military is very popular with its flat ground blade. This is somewhat "new" territory for Spyderco, maybe it is just taking a while for people to convert. It seems that knife junkies tend to be a little ahead of the general ELU populace so maybe it will just take a little more time. Perhaps the Calypso Lite will change some minds. I'm hoping, because it is a trend that I like. I'm hoping the Lum Chinese knife will be flat ground if we ever see it come to completion (what with the abundance of SKUs existing). Please tell us Sal before you discontinue the Calypso Jr BM!
Paul
 
Hey guys I made a typo, I meant that I prefer Flat Ground, performance wise. OOPS!
 
Ah! I see, Sal.
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I was kinda disappointed to see the flat grind only used in the micarta version. I like the heavy weight of the stainless along with the flat ground blade. Ah well.
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Its all good.
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Mike
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------------------
Hey! Uncle Sam!

(_!_) Nyah nyah nyah!

Refund! You lose! :)


 
Paul - The flat ground Bob Lum Chinese folder is on the Y2K schedule as a new model. Hope to have early shipments in at year end. the plan is for a Rolling lock. We're still discussing handle materials. Original protos were made with Titanium. Any preferences among the forumites?
sal
 
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