Are hollow grind blades weak?

L

LikeHike

Joined
Feb 23, 2006
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I am thinking of getting a Spyderco - probably a Native - which looks like it is hollow ground. It brings up a few questions for me about hollow ground blades. I do not have much experience and hope for some help.
Thanks.
Everything being equal - the shape of the blade, steel, heat treatment, etc. - are hollow grind blades substantially weaker than a flat or convex grind?
Does it make much of a difference in typical usage?
Is a hollow grind blade a poor idea for a survival type knife?
 
I have never had a hollow ground blade chip and have only had one instance of having the edge roll over. All of my hollow ground blades are EDC folders and are used for slicing. For chopping I would never choose a hollow ground blade, as I do not think the edge would hold up.
 
Spyderco... ground... blades... weak...? I wish that were the case. Then they would cut a lot better. I find most of them too thick.
 
"Blade geometry FAQ" and "Steel FAQ" (on the same site) by Master Joe Talmadge. You will find there the response to the majority of the questions.

dantzk.
 
from my experience I have had no problem with hollow ground blades as long as you are using them for cutting. If you decide to use it for a crowbar, jackhandle, etc then I can see where you may have a problem. As for the native, go for it. I've got one of the wally world specials and It's almost sexonastick. as usual your results may vary. later ahgar
 
I'm OK with hollow ground blades on folders and small pocket fixed blades. Convex and flat grinds are better in bigger knives that will be used hard, chopping, battoning, etc. I don't think you'll be able to to something to the Native that will hurt the blade during regular use.

FYI, one of the old standards for working folders, the Buck 110 has a hollow ground blade, IIRC so does the mighty Sebenza.
 
Keith Montgomery said:
For chopping I would never choose a hollow ground blade, as I do not think the edge would hold up.
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I may be wrong, but I don't see how the hollow grind of the knife would have any effect on edge holding. As long as a flat ground and a hollow ground knife were both sharpened at the same edge angle, and the thickness of the steel behind the edge were identical, edge holding should be identical.
 
Buzzbait said:
As long as a flat ground and a hollow ground knife were both sharpened at the same edge angle, and the thickness of the steel behind the edge were identical, edge holding should be identical.
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It's the difference between a thin wall and a pyramid of equal height. A hollow ground blade chopping at any but the exact perdendicular angle will be under pressure to roll over. A flat ground (scalene-triangular) edge will be backed up even at slight variants of that perpendicular stroke.

Even so, I'm sure we can all think of large, hollow ground knives that are used routinely for chopping, folders and fixed blades. It's a matter of technique, as well as geometry.
 
kel_aa said:
Spyderco... ground... blades... weak...? I wish that were the case. Then they would cut a lot better. I find most of them too thick.
Click to expand...

The Centofante is a thin slicer.
The Kiwi is a great Wharncliff cutter...
and the Jester/Ladybug surely aren't very thick in absolute terms.
I mean, Spyderco isn't Strider or Extrema Ratio!
 
There is currently a thread going above this one titled "Spyderco Native Chipping Issues". There seems to be some issue with some knives. The discussion is more around the S30V than the blade grind. Could the hollow grind be a contributing factor???
Guess I will ask this there as well.
 
Buzzbait said:
I may be wrong, but I don't see how the hollow grind of the knife would have any effect on edge holding. As long as a flat ground and a hollow ground knife were both sharpened at the same edge angle, and the thickness of the steel behind the edge were identical, edge holding should be identical.
Click to expand...

Wasn't referring to edge holding. What I meant was that the edge would be prone to chips and dents.
 
The Centofante is a thin slicer.
The Kiwi is a great Wharncliff cutter...
and the Jester/Ladybug surely aren't very thick in absolute terms.
I mean, Spyderco isn't Strider or Extrema Ratio!
Click to expand...

I agree there are some full flatground and deep hollowground Spydercos with cutting very much in mind (say a Military, or the noted Centofante). However, I don't think there is any reason why the basic lineup, Delica, Endura, or Native and such cannot be full flat ground. When was the last time you broke your SAK blade or Opinel or some other slipjoint and wish you had a thicker saberground blade? Yes, slightly thicker blades have their strengths, but I find most of the time the extra blade is a liablity (compare skinning a melon wedge between say a Delica and a Opinel. Guess which one is like trying to split a log).


Wasn't referring to edge holding. What I meant was that the edge would be prone to chips and dents.
Click to expand...

Your secondary grind should be several mm deep. If you are chipping and denting the blade all the way to the primary grind, then you should probably revise the way you handle knives in regular use. If it doesn't chip all the way to the primary grind, then the primary grind is not the issue. In any case, you can increase the edge angle to boost your secondary grind strength.

Today I'm taking my stand against the thick uncutting knives.
 
The discussion is more around the S30V than the blade grind. Could the hollow grind be a contributing factor???
Click to expand...

I say no no no. Using the pyramid analogy someone brought up earlier, the very tip is only 1 stone. If you take a jackhammer to that capstone, it doesn't won't matter how massive the base is, that stone will break.

Of course you wouldn't want to stack up stones without a progressively wider base (in some fashion). But that is hardly ever the concern in any knives you see, save for prehaps the Falkiven U2 Cliff got someone to hollow grind.
 
LikeHike said:
I am thinking of getting a Spyderco - probably a Native - which looks like it is hollow ground. It brings up a few questions for me about hollow ground blades. I do not have much experience and hope for some help.
Thanks.
Everything being equal - the shape of the blade, steel, heat treatment, etc. - are hollow grind blades substantially weaker than a flat or convex grind?
Does it make much of a difference in typical usage?
Is a hollow grind blade a poor idea for a survival type knife?
Click to expand...


Too weak for what? Cutting things or prying open old paint cans? What?

http://forums.egullet.com/index.php?showtopic=26036
 
Buzzbait said:
I may be wrong, but I don't see how the hollow grind of the knife would have any effect on edge holding.
Click to expand...

In general, as blades cut better they have better edge holding for a variety of factors, you can in general raise the cutting ability with hollow grinds and thus the edge holding is usually increased. The exception is in chopping because of the way forces are distributed across the edge in impacts, a deep hollow grind tends to twist in woods and doesn't initiate splits readily. A convex/flat primary profile can open up chips during impacts which reduce the wear/impacts against the edge. Hollow ground hardwood axe axes are exceptions to this general rule but on them the edges are so wide that they behave much like the primary grinds on knives.

kel_aa said:
If you are chipping and denting the blade all the way to the primary grind, then you should probably revise the way you handle knives in regular use. If it doesn't chip all the way to the primary grind, then the primary grind is not the issue. In any case, you can increase the edge angle to boost your secondary grind strength.
Click to expand...

Exactly, the link of hollow ground = edge chipping is false for exactly those reasons you noted. This however is in published books, and thus you will continue to hear it for a very long time. It probably surfaced because in general hollow ground blades have thinner edges and angles than flat ground blades or convex, compare a straight razor to chef's knife to cleaver for example.

As to the origional question, yes if you put a deep hollow ground on a knife it will weaken it significantly. With survival knives the main problem is the edge isn't supported, so if you do blow the edge on a hard impact, the primary grind can rupture. It also is prone to edge overloading in prying and you can get large blowouts which are much more difficult to do on flat/convex blades, for example :

http://www.physics.mun.ca/~sstamp/images/solution_cracked.jpg

Those large circular notches came out just light prying in hardwoods.

-Cliff
 
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