Hollow Grinds - Meh!

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pinnah

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We had a fire in the fire pit behind the house tonight. I took the opportunity to practice a 1-match light with no paper (it worked) which meant cutting down a bunch of shavings for tinder. For grins, I thought I would put a couple of hollow grind knives up against my Opinel #10, which has a convex grind. The 2 hollow point knives were a Case 316-5 fixed blade (5" blade) and a Buck 112 (3" blade). Both were sharp and the 112 was hair popping fresh off the Lansky.

The result wasn't even close. We're talking about huge, obvious difference. Men and boys or pros and amateur differences. The Opinel easily cut off large shavings in easy, controllable strokes. The hollow grind knives balked and skittered and when then they cut, bound up easily in the wood.

I use the Case in the kitchen for cutting meat and it does fine there. But, the Opinel just as good at that too.

This leaves me to conclude that there really is no situation I can think of where I prefer to cut with these hollow grind knives if I have the Opinel to use. And when wood is involved, the preference isn't even close.

Tim Smith at Jack Mountain Bushcraft notes that (paraphrasing), a fire can save your life, so the definition of a survival knife one that can reliably and easily make shavings. Of the knives I own, it's the Opinel #10.
 
Opinel is hard to beat. My 10 gets plenty of use, but I will say that the puukko is better with the shavings. Of course, it is not hollow ground either...
 
I am not a huge fan of the hollow grind either.

Full flat. Usually with a convex edge.
 
I can imagine that a hollow grind is best suited towards something you might use a razor for like skinning game. In use I generally prefer a flat grind, but I have to say my sharpest knife is a hollow grind
 
Handle a hollow ground Rick Menefee knife sometime, you'll change your mind. I've never felt anything sharper on earth and for slicing just cannot be beat.
 
Hollow grinds seem to be great slicers, but are better left to straight razors and skinning knives IMO. They bind in heavy wood work and don't offer any advantage over a flat or scandi grind to me. Flat is my choice :D
 
Specifically regarding the binding of the hollow-grind blades in the wood:

Sometimes, just adding a slight convex to the (previously) V-bevelled edge on a hollow-grind blade can make a huge difference in how the blade cuts through tougher material, like wood and cardboard. It didn't take too long for me to notice that just rounding off & smoothing the shoulders can really reduce the friction (binding) one encounters in cutting cardboard and wood. The hard shoulders of the V-bevel, not necessarily the hollow grind of the rest of the blade, are where most of the binding issues are generated.

I have and use a lot of Case's pocketknives, most of which are thin hollow grinds. I've been maintaining everything with the sandpaper over my strop block, so they all have that little bit of convex to them at the edge, and the improvement in cutting (reduction of friction) is noticeable, even on those small & thin blades. It's especially apparent when comparing to Case's factory V-bevels, which often leave some seriously big burrs at the shoulder of the bevel, which will obviously grab & bind on any material with which they come into contact.

Putting a slight convex on the edge is as simple as 'stropping' it on some medium/high grit wet/dry sandpaper. Just enough to erase the hard edge of the shoulders on the bevel.
 
Ummm...your pardon, but I am a bit confused as to what is being compared.

It's always been my understanding that:
* "Hollow ground" applies to the body of the blade and is compared to "flat ground",
* "convex" applies to the edge and is compared to "v-edge".

So are you actually comparing the edge sharpening method or the blade shape?
 
knarfeng said:
Ummm...your pardon, but I am a bit confused as to what is being compared.

It's always been my understanding that:
* "Hollow ground" applies to the body of the blade and is compared to "flat ground",
* "convex" applies to the edge and is compared to "v-edge".

So are you actually comparing the edge sharpening method or the blade shape?
Click to expand...

As I interpreted it, his comparison is between blade profiles (primary grind), as opposed to the secondary bevel at the edge. Regarding the Opinel specifically, the whole blade is a subtle, thin convex, and usually with a small V-bevel at the very edge (from the factory). I personally think some of both factors, the primary blade grind (hollow vs. convex) and edge grind (assuming a V-bevel on the hollow grind blade, at least), are playing into the cutting results he mentioned.
 
I think the OP compared a knife that is known for thin blade,thin grind behind the edge,to two knives,that are just so,so grinds.
Some blades are ground thicker,some thinner. But how can you compare a thinly ground flat ground blade to a not as thin hollow ground blade,and conclude that the flat grind is the WTG for you,but in reality ,that particular blade had better edge geometry.

I personally like good cutting blades weather flat or hollow ground
 
Case, and especially it seems, Buck edge bevels can be significantly thicker and less acute than Opinel. As a result, it's not surprising an Opinel would excel over others in many instances, regardless of the type of primary grind.
 
shecky said:
Case, and especially it seems, Buck edge bevels can be significantly thicker and less acute than Opinel. As a result, it's not surprising an Opinel would excel over others in many instances, regardless of the type of primary grind.
Click to expand...

This is the exact opposite of my impression. In more recent years (post-2000 anyway), most of the Case edges I've seen are very acute, and Buck's definitely so. Buck introduced their 'Edge 2000' grind (think that's what they call it) in the same-named year, and that was specifically aimed at (or resulted in) making their edges much more acute than previously. The thin convex blade on Opinels does make for great slicing, but the factory edge bevels (almost micro bevels) on mine, when I received them, were pretty thick and almost blunt.
 
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I've not mastered convex sharpening. All 3 knives are sharpened on my Lansky at 20 degrees. My 112 is an older 3 dot and has the old Buck thicker bulge behind the cutting edge. I pretty aggressively broke in that blade at 17 degrees first. I should also mention its shoulder is very rounded. Distinct, yes. But rounded.

While I know I'm not taking full advantage of the Opinels blade profile due to my standard sharpening (I do strop it regularly) it really plows through wood.

I would have to think a part of it is the splitting wedge shape of the blade.
 
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My feelings on hollow ground blades are also based, in part, on how big the wheel is.

I just felt a "hollow" ground knife by J Oeser, a custom maker out of Utah.

He uses a radius-ed platen attachment that equates to a 36 inch wheel. It is very close to a flat grind, and he takes that primary grind down THIN before adding the sharpening bevel.

This grind was very impressive.

I am sure that many makers, including old manufacturers had methods for making these types of grinds perfect.

Very sharp!


With a very nice thin primary grind, even a more obtuse final angle will cut well. (IE, if you take an Opinel, and sharpen it at 30 per side (60 inclusive) it will slice better than a knife with too much meat behind the edge will at 15 per side (30 inclusive)

I feel like most manufacturers (and some custom makers) leave the primary grind much to thick.

The result is a knife that won't slice like you think it should, where the blame lies, not with the type of grind, but with the geometry used.

Hollow grind, Saber hollow, Saber flat, convex, flat grind to v edge, or full convex grind to zero edge......... All will cut if the geometry is ok.



Obsessed with Edges said:
This is the exact opposite of my impression. In more recent years (post-2000 anyway), most of the Case edges I've seen are very acute, and Buck's definitely so. Buck introduced their 'Edge 2000' grind (think that's what they call it) in the same-named year, and that was specifically aimed at (or resulted in) making their edges much more acute than previously. The thin convex blade on Opinels does make for great slicing, but the factory edge bevels (almost micro bevels) on mine, when I received them, were pretty thick and almost blunt.
Click to expand...

I just bought my first Opinel. One for me and one for my 7 year old son. The grind is nice and thin. The final edge angle/micro bevel was not overly sharp. It would not shave hair, even with a lot of pressure.

However, it was perfect for a knife for my son!

I took mine, and did about 4 strokes per side on my diamond stone, followed with a few light passes per side on the ceramic sticks, and it was nice and sharp.

When I get a moment, I will take the edge to a convex polished edge.

The primary grind was so nice and thin....I will be buying more!
 
pinnah said:
The result wasn't even close. We're talking about huge, obvious difference. Men and boys or pros and amateur differences.
Click to expand...
Sounds like it was more of a men and little girls difference to me. That's been my experience too, although the one more than 2 inch convexed knife I own doesn't really do well at woodwork. It's almost as bad between a good full flat or high saber and hollow.
 
pinnah said:
I've not mastered convex sharpening. All 3 knives are sharpened on my Lansky at 20 degrees. My 112 is an older 3 dot and has the old Buck thicker bulge behind the cutting edge. I pretty aggressively broke in that blade at 17 degrees first. I should also mention its shoulder is very rounded. Distinct, yes. But rounded.

While I know I'm not taking full advantage of the Opinels blade profile due to my standard sharpening (I do strop it regularly) it really plows through wood.

I would have to think a part of it is the splitting wedge shape of the blade.
Click to expand...

Does your 3-dot 112 still have a V-bevel for the edge itself, aside from the rounded grind above it? Reason I ask is, I have an old 2-dot 112 (440C) with the same thick(ish), but still hollow blade grind. I originally hated the factory edge on it, but finally got around to convexing & polishing it down to a zero-grind edge (no V-bevel or micro bevel). This is the first knife that really opened my eyes, in terms of how much difference just getting rid of any hard corners on the bevel will make. It's a cardboard-eating demon now (very slick at 2000+ grit polish), and I'm sure it would perform equally well in wood.

I do agree, the 'splitting wedge' shape of a good convex really makes a difference, and that's sort of what I got from the convexing of my 112, as described above.
 
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In my opinion(which is like the butt everybody has one) the thing is like this:
-For woodworking Scandi grind to a zero edge is by far the best, hands down no contest here
In the question ask by the OP, I think it isn't a fair comparison anyway because the start point in thickness vary a lot and the opinel is the winner here but only for the geometry or blade profile.
in the matter of hollow ground vs flat ground taking all variables equall, I mean grinds well done, same steel, same hardness, etc. I find hollow ground slightly easier to sharpen(less material to remove) and really think that it's a company decision to make this kind of blade profile easier to do at a factory level and easy to resharpen for the common user.
Regards
Mateo
 
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