Full Flat Grind vs Hollow Grind

Lenny

Lenny

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Oct 15, 1998
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OK, let's settle this here and now.
Educate me please.
What are the benefits and drawbacks of each grind?
Assuming the same blade steel in 2 knives, one flat ground, one hollow ground, which is better for what type of cutting tasks?
Thanks all.
Lenny
 
Well, both slice very well but flat grinds are generally less fragile or less succeptible to chipping. I personally prefer full flat grinds over hollow since they are usuaully more robust and I think they perform a little better.
 
I'm actually pretty sure hollow grinds are easier to do with production knives.
They slice better than a flat grind but chip easier.
 
In my experience, a hollow grind can get crazy thin and sharp. They are easy to do because (this is what I have gathered in from my time on the forums, it might be wrong) the blank blade can be ground on both edges at the same time. Flat grinds are great slicers. Some FFG blades I have are great slicers and seem a bit more robust than some hollow ground knives that I have experience with. My desert sand Leek and Native are hollow ground and they get crazy sharp, but I'm afraid to accidentally drop because the tip or edge might break.

For me, it really doesn't bother me what the grind is but I lean towards FFG.
 
FFG will be stronger. A properly done hollow grind with a thin edge bevel and a high hollow grind will cut like nobody's business. The chipping observation noted above is a function of edge bevel angle and thickness (as well as steel and heat treat), not a function of hollow grind vs FFG.

Not all hollow grinds are created equally, and not all FF grinds are created equally. Blade stock thickness, edge bevel thickness and angle, and height of the hollow grind all have significant influence on the cutting performance.
 
Hollow grinds and FFG are great grinds for cutting with FFG usually being the better slicer. Hollow grinds have full spines while FFG dont so you could say hollow grinds have the best combination of cutting ability and spine strength. FFG will have stronger edges since they have more steel behind them. Honestly its hard to say ones better than the other.
 
Hollow grinds will be thinner at the edge so they will slice better and be easier to sharpen. They will be more susceptible to chipping, though, so they're better done with a tough steel like M4.
 
Hollow ground and full flat both have their place, but don't overlook convex ground blades.





Big Mike
 
+1 on the convex big mike. a ffg with a convex edge done right can be wicked sharp. you can put a convex edge on a hollow ground knife and end up with an edge that can scare you.
 
Based on my experience, the ranking is pretty simple.

Slicing tasks:
1. Hollow
2. Full Flat
3. Convex

In each case a zero grind is superior to a secondary grind. ie a hollow grind all the way to the edge will slice better than a hollow grind + secondary edge bevel, and a full flat grind all the way to the edge will cut better than a ffg with a secondary bevel. Of course, a very thin convex edge will slice better than a thick hollow grind.

Chopping tasks: Just the reverse
1. Convex
2. FFG
3. Hollow

FFG offers a middle ground between strength and slicing and is preferred by many people for a general purpose blade. Personally, I really like the high but shallow hollow grind on the boker exskelibur. For a hatchet or large chopper, convex is the way to go.
 
Something else is that a hollow grind is nice when making shallow cuts where the spine does not pass through whatever is being cut. I prefer a FFG when making deeper cuts as it won't bind up in what I am cutting. A hollow ground knife may not slide through the material as easily depending on the spine thickness and how high the grind goes on the knife.
 
To me, the grind of a knife is a lot like ammunition ballistics. In this scenario:

9mm vs 40s&w vs 45 acp : hollow ground vs flat ground vs convex

A lot of people go with the middle, but I go for the tail ends.
My handguns: 9mm and 45acp.
My knives: hollow ground and convex.

I don't have time for the "middle of the road" yippity splikkity. I got different tasks to do. If I'm cutting/slicing, then I go with hollow. If I'm chopping/splitting, I'm going with convex. Let me not lie about this though. I do have some FFG simply because I think the knife looks sweet.

Edge holding argument is another matter that matters more to me on steel type and characteristics (RC, HT, etc). If I take a hollow ground blade and slam the edge on concrete, I expect it to roll, if not slightly chip. Heck, I've seen VG-10 slightly chip and I think it's an excellent steel.

So my answer to the OP's question/debate is this: I'd rather go convex than FFG. Otherwise, gimme the hollow.

+1 to Chocula as well.
 
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It really depends on how it's done. The hollow grind on my H1 salt knives aren't anything special compared to FFG. However, the hollow grind on my Spyderco Gayle Bradley and Sebenza makes them the best cutters I have. I think it also depends on what you're cutting.

Some people have posted pictures showing how a convex edge has more ease of cutting because of less drag due to the curvature. I think the same applies for hollow grinds also due to the curvature, as I find less resistance when cutting apples between my Para2 and Sebenza. And while the edge on that S90V blade doesn't seem to dull from cutting cardboard, I notice a hell of a lot of drag when cutting a particularly long and sturdy piece.

It's important to make the distinction between a high hollow grind and the typical hollow grind that only overs half the blade width.
 
All else being equal(edge geometry, stock thickness, etc), the hollow grind will be better on shallow cuts that do not exceed the height of the grind, since cutting ablity in those instances is determined by the edge and how much material is directly behind it, while the flat grind will perform better on deeper cuts that put the entire blade width into the cut.
The consistency of what is being cut will have some effect, too. On deeper cuts, some materials with little give can be wedged apart by a flat grind, but bind at the top of a hollow grind, while something with more give might practically stick to a flat, while a hollow grind passes through more easily.
What blade geometry performs best tends to depend on what you're cutting.
 
I haven't really noticed a terrible amount of difference, but from what I've noticed slicing blocks of cheese, my FFG seems to bind less passing through material like that than hollow or sabre grinds. It's as if the FFG keeps the material off the secondary grind of the knife through the cut.
 
Generalizations fail too much. For most users, unless one needs high impact and/or lateral force durability (you want a chopper and/or prybar), there will be no difference, other than cosmetic.

Assuming identical blade thicknesses, real differences in cutting aren't usually from the type of primary grind, (full or saber, hollow, flat, or convex). The biggest noticeable difference is the acuteness and thickness of the edge bevel rather than the primary grind.
 
I think a lot would matter on how thin the grinds are as in how thick they are behind the edge.

It's really hard to beat a FFG that is ground to .010" or less behind the edge with a thin spine....
 
This thread really needs to specify if they are talking about FIXED blades or FOLDERS, this is the thin red line for me, i like a convex fixed blade on ALL my fixed blades but all my folders are FFG or Hollow, really to me doesnt make a huge difference unless im using the folder to cut something like an apple i choose FFG everytime. Hollow grind to me is only a personal added (not needed) preference, no need for it IMO. Some people will sware by it but iv NEVER found myself using a FFG knive thinking, "man I sure with this was a hollow grind" < Never happened, not once. but thats just me.
 
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