Hollow Grind Vs. Flat Grind

[UltraSteele]

Okay Folks, I have a question.

Why do we use hollow ground blades anymore? Aren't flat ground just better for almost anything but meat cutting?

Tell me what YOU prefer, and why.

I prefer Flat grind because I've found it cuts everyday materials- rope, carboard, oranges, and wood- better than a hollow ground egde.

 

[W.T. Beck]

Some people say the convex grind is best.

 

[Cliff Stamp]

I prefer Flat grind because I've found it cuts everyday materials- rope, carboard, oranges, and wood- better than a hollow ground egde.

Hollow grinds can be made to cut that better, a lot of hollow grinds are just too thick and shallow to do so, like the low hollows a lot of tacticals like TOP's and Strider run.

-Cliff

 

[phatch]

Cliff's comment is what keeps me off of many Spydercos, even though they are good knives. I'm not fond of the hollow grind either for most of my cutting. And even thin stock blades and a low grind height like Spyderco still cause me problems.

I admit, a lot of my cuts are deep. Hollow grinds hang up/bind in that cut or fracture what I'm cutting like apples, and carrots.

Phil

 

[Cliff Stamp]

Yes, this is mainly due to how it is done. McClung had a rant on hollow grinds vs flat grinds which lambasted the hollow grinds as mainly being a cheap monetary excuse, but what he was actually comparing was full height grinds vs shallow sabre ones, and the respondent edge geometries are usually different as well.

A shallow sabre ground TOP's with a thick and obtuse edge compared to a full flat Paramilitary does make hollow grinds look like poor cutting blades, however there are also lots of flat ground blades that won't cut either. The Fulcrum is flat ground, and is one of the worse cutting tools I have seen.

But there is no reason why a hollow grind has to be like this, take your favorite flat ground blade and apply a hollow right on top of the flat which can either radically sweep out the edge to maximize shallow cutting, or just break the surface to reduce wedging.

Japanese kitchen knives typically have the second type of hollow and they cut amazing. To truely appreciate the performance of extreme hollow grinds you need a very thin blade, 1/16" stock, full hard steel, and a very deep hollow grind which leaves almost no steel on the edge or behind it.

I recently had a U2 converted from full flat to hollow to increase the cutting performance and ease of sharpening.

-Cliff

 

[STR]

It really does matter as to the grind and to a large extent who did it too I guess. I have hollow grinds that cut great, like those from Bob Dozier and some that are flat out worthless. Same with flat grinds. But I too prefer the flat.

First off I think the flat in most cases is stronger but certainly not all. In a smaller knife that may not be an issue but in a bigger one it is I think. I know I prefer the Cold Steel Vaquero flat grind to the Voyager's hollow hands down for yard work and cutting small branches. I've chipped the Voyager doing jobs the flat grind Vaquero eats right through. But these are big knives. (the x large ones.)

 

[GarageBoy]

Try the Centofante III, redefined hollow ground for me

 

[allenC]

I think that there is alot more to cutting performance than the "flat or hollow" choice.

It's more about specific blade design IMHO.

My hollow-ground Centofante III outcuts my flat-ground micarta Calypso Jr, but they also have different blade thicknesses, different blade-steels, different edge lengths, different blade shapes, and different handle designs.

So...I really can't recommend one grind over the other.

But I will say that, all things being equal, a thinner blade usually slices better than a thick blade.

Good luck,
Allen.

 

[STR]

Cliff's comment is what keeps me off of many Spydercos, even though they are good knives. I'm not fond of the hollow grind either for most of my cutting. And even thin stock blades and a low grind height like Spyderco still cause me problems.

Phatch you must be one of just a few that have a problem with Spyderco's cutting ability. (if I read your statement correctly.)

Spyderco knives sometimes drive me knuts, with the likes of blade play vertically and sometimes laterally that is 'deemed normal' or 'within tolerance levels'.

At times I've had two Delicas and/or two Salts and/or two Enduras and one would have vertical blade play and the other would be rock solid but both were acceptable or 'passed' and both were new. At first it took me a while to get used to this and for the longest time it was why I absolutely refused to order any Spyderco on line or from a catalog.

If I couldn't play with the knife first to make sure it locked up right I didn't want it. But I finally lost my only knife dealer in town and had no choice if I wanted to own Spydercos so I took the chance and ordered on line. When I bought new I've bought from A.G. Russell, New Graham, Fred at Knife outlet, and more. When I buy used the first question I ask anymore is, "does the knife have vertical blade play when you open it?"

So far I've been batting about 50% or so with knives showing blade play in one way or another from Spyderco. My Manix, Chinook, CJ, Delica, Salt 1 PE and Native all had some vertical blade play from the minute they were first opened to my disappointment but over time I learned to over look that because the damn things cut so well and in most cases the blade play was noticeable but minute.

My current Salt 1 SE locked up so solid you couldn't make it move though, as does my Catcherman, and so did the Viele 2 I owned and the Para-Mil and the Tan Endura, and both my stainless Endura and my stainless Delica.

I tell ya, if these Spydercos didn't cut so good I'd probably not be using them to be honest because of this frequent blade play I've seen, but I read later that Sal said in Spydercos tests the locks held up better with just a tad of blade play compared to the ones that didn't have any play at all. I still have a big question mark about that to be honest.

Spydercos have such good edge geometry right out of the box that it is hard to find fault with them unless the vertical blade play is such that you can feel the blade move up with your thumb when you open the knife. Then I get irritated and in a couple of cases the knife was returned and replaced.

 

[djolney]

I like both grinds, but have noticed some significant differences.

Flat ground blades can get stuck in material when chopping, whereas hollow ground blades seem to break there own way out.

Hollow ground blades give you the advantage of a thin edge and strong spine in the same package, whereas flat ground blades can leave a lot of potentially unnecessary steel in the middle.

Hollow ground blades are easier to sharpen for longer. It takes a lot of use to get beyond the thin edge, whereas with a flat ground blade you start removing lots of steel from the side quite quickly.

 

[digdeep]

Would a hollow ground blade be practical on a heavy duty chopper like a Ranger, Becker, or Swamp Rat fixed blade?

Wouldn't the hollow grind compromise edge strength compared to a flat grind?

 

[djolney]

Would a hollow ground blade be practical on a heavy duty chopper like a Ranger, Becker, or Swamp Rat fixed blade?

Wouldn't the hollow grind compromise edge strength compared to a flat grind?

My Ranger Knives RD7 and RD6 (custom in 3V) are both hollow ground. They are tough enough to take any task I’ve put them to, and I don’t think Justin would have ground them the way he did unless he thought a hollow grind was up to the job.

My Chris Reeves are hollow ground, and they have survived regular hard use without problems.

IMO, hollow grinds give you the best of both worlds: a strong blade with a good fine edge for cutting.

 

[Cliff Stamp]

I think that there is alot more to cutting performance than the "flat or hollow" choice.

Yes, you can't ignore how it is ground, look at the cross section of the blade. There are general differences though, you can't make a good wood splitter with a hollow grind.

Phatch you must be one of just a few that have a problem with Spyderco's cutting ability.

He referred specifically to the low saber hollow grinds in deep cutting, they are not optimal for that, the higher flat grinds work better there.

Flat ground blades can get stuck in material when chopping ...

This is more as to how they are ground. Wood splitters for problematic wood are actually flat ground.

Hollow ground blades are easier to sharpen for longer.

Yes, a nice deep hollow grind can leave the edge at almost the same thickness for a long time, if they are really thin ground they are also easier to apply really acute angles.

[heavy duty chopper]

Wouldn't the hollow grind compromise edge strength compared to a flat grind?

The edge strength depends more on the thickness of the edge. You can easily put a hollow grind which leaves a very durable edge if you leave enough material.

There is a problem in regards to extremes, due to the edge support issues, hollow grinds can be prone to rippling and/or penetration into the primary grind.

Again though you need to be really careful with generalizations, and look at the thickness. Justin for example grinds his edges with enough support so that neither of these are a concern.

I would prefer a high flat grind for that class of blade though which Justin is running now on the RD series.

-Cfiff

 

[phatch]

Phatch you must be one of just a few that have a problem with Spyderco's cutting ability. (if I read your statement correctly.)

I'm not saying Spydercos don't cut well in general, I'm saying they don't cut well for my purposes in a knife. I've not used a flat ground folding Spyderco and those do tempt me. I like my Spyderco Santoku and it cuts very well for its price.

I'm saying that the many Spydercos that are hollow ground with a low grind height (Delica, Endura) don't cut the way I want to cut things, especially in deep cuts.

Phil

 

[Habeas Corpus]

I'm saying that the many Spydercos that are hollow ground with a low grind height (Delica, Endura) don't cut the way I want to cut things, especially in deep cuts.

Get one of the Spydercos with a flat grind then, for instance a Calypso Jr., and give it a try. The difference compared to the Delica for instance is *very* noticeable.

Hans

 

[OwenM]

IMO, which grind is better depends on the thickness and consistency of whatever is being cut. Every time you cut something, you are wedging material apart.
How that material responds to being "split" decides which grind is better for cutting it.

For instance, the two folders I use the most are a small Sebenza and a Spyderco Paramilitary. They are pretty similar in edge geometry, the Paramilitary's actually being thinner because of a back bevel. The length of their actual cutting edges is almost identical, and so is their overall thickness when you get ~5/8" behind the edge where the Sebenza starts sweeping up to meet the top of the grind(it's thinner before that, thicker afterwards).
On something thin, like packing tape, cord, a plastic bottle, plastic sheeting, paper, thin cardboard, etc. I can't tell a difference. Those items' thicknesses rarely exceed the height of the edge bevel itself so the grind really doesn't come into play.
On heavy hose with neoprene rubber inside a thick and harder shell, like I cut frequently at work, the Paramilitary binds, 'cause the shell is hard to cut through initially(more resistance because the Para's flat grind is thicker behind the edge whose height the shell's thickness exceeds), plus the rubber core "sticks" to the blade, and makes it harder push/pull through. It is not soft enough to conform to the Sebenza's hollow grind, which is thinner behind the edge and cuts right through both layers.
On things that are thicker and/or more rigid, and retain their shape, like cutting thick cardboard, or even something like sectioning a lime, the Sebenza binds because its thickness increases quickly at the top of the grind, faster than the edge's(or grind's) wedging action can compensate for once the cut gets deeper than the grind.

All else being equal, the hollow grind seems to do better on shallow cuts that do not exceed the height of the grind, since cutting ablity in those instances is apparently determined by the edge and how much material is directly behind it, while the flat grind does better on deeper cuts that put the entire blade width into the cut.

 

[allenC]

Phatch,

"I'm saying that the many Spydercos that are hollow ground with a low grind height (Delica, Endura) don't cut the way I want to cut things, especially in deep cuts"

Maybe you should give the Endura and Delica another chance--they are no longer hollow-ground (changed around 2002 to flat-grinds).

Good luck,
Allen.

 

[Cliff Stamp]

All else being equal, the hollow grind seems to do better on shallow cuts that do not exceed the height of the grind, since cutting ablity in those instances is apparently determined by the edge and how much material is directly behind it, while the flat grind does better on deeper cuts that put the entire blade width into the cut.

The hollow grinds like on the Sebenza behave this way, and for some media the wedging can be severe. I have had hollow ground chopping blades stick in wood so badly I had to actually beat them out with a stick. However not all hollow grinds are of this type. Consider :

http://www.physics.mun.ca/~sstamp/images/grinds.xfig.gif

The blade on the far right is a hollow grind which won't wedge compared to the corrosponding flat grind (far left), if anything it does better on deep cuts because of a reduced friction.

-Cliff

 

[Jason Cutter]

I prefer flat grinds, just intuitively. However, I think any choice is simply a choice of the best combo of compromises for your situation. LIke most of you, I am bothered by the tendency of shallow and sabre ground hollowgrinds to wedge in HARD materials. I own many factory made knives with such a grind profile, that work perfectly well in situations where I am only cutting with the very edge, and not slicing. Or slicing soft materials like meat, is perfectly fine as the meat falls away from the blade without wedging.

I have worked with flat grinds, shallow convex edges and tall, thin hollowgrinds and they all have valid cutting applications.

A word on "hollowgrinds being stronger than flat grinds." This is perhaps a misinterpretation of the H-beam or I-beam concept. The H-beam concept is that a H-beam construction will be stronger and stiffer than a uni-dimensional flat bar of the same WEIGHT. The uni-dimensional flat bar will be of completely different dimensions. A flat ground blade with the same edge and spine thickness as a hollowground blade of the same dimensions, will be stronger simply because there is more steel in the middle. A convex ground blade will be even heavier and stronger. Period.

My 2 cents. Jason.

 

[sodak]

The dimensions of an I-beam determine it's strength. It will not be stronger than a solid piece of steel of the same dimensions. That's a common misperception. The design of an I (or H) beam simply remove unnecessary metal, and make it lighter. The strength is the same.