Full Flat Grind vs Hollow Grind

DrJackson said:
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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The thing with a hollow grind is that you can have a thicker spine for added strenght and it can still slice well.
 
Ankerson said:
The thing with a hollow grind is that you can have a thicker spine for added strength and it can still slice well.
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This is exactly what I was going to say, but then for the ultimate add a convex secondary bevel. For making deeper cuts, the convex bevel moves material away from the primary bevel reducing drag and making slicing easier and more efficient (less binding).
 
Ankerson said:
The thing with a hollow grind is that you can have a thicker spine for added strength and it can still slice well.
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That combination hinders a hollow ground blade's slicing abilities. If the substrate being cut is taller than the blade is wide, the blade will bind. A thick spine adds no strength to the edge.
 
Is there a pictorial diagram to show what they should look like to a newbie?
Thanks.
 
As stated below, a hollow ground blade will have a very thin secondary, or relief grind. This makes for a scalpel sharp edge for slicing shallow items, that do not pass the spine, which is much thicker. Slicing paper or meat is great, but try to cut an apple, the edge glided right through the apple, but when it gets to the spine, it acts like a wedge & pushes the already cut part away from each other. it will split the apple more than cut it. That is why most kitchen knives are full flat ground.
If you can find a knife with the hollw grind that goes all the way up to the spine, it will be great.
I do not care for saber grind knives, where the grind only goes up 3/4 of the way up to the spine, I dont care if it is hollow grind or flat grind, the knife I want is a FFG or full flat ground blade that goes all the way to the spine.
A good example would be a spyderco delica, they were first made with a saber grind, and I think it was flat ground 3/4 up to the spine.
They now make a FFG spyderco delica, that will cut rings around the sable ground version.
Hope this helps.
Uncle Knife
 
Very interesting topic
Can someone provide some pictures to illustrate the difference? This will be very kind ... And helpful to understand the differences discussed here
 
The best imo is neither. A high and thin flat grind gives you great slicing without as much drag as a hollow ground and is thinner at the edge than a typical ffg while still giving you a lot of tip strength.
 
Fixed - convex grind with convex edge
Kitchen - ffg with flat edge (convex works too)
Folder - hollow with convex edge
 
For me I like a FFG blade with a double distal taper and .005-.010" behind the edge done on a stone for easy maintenance. Convex edges are fine, but are more difficult obtain. Some people think they are sharpening their convex edges properly, when in fact all the are doing is adding a flat micro bevel to the edge.
 
Technically my convex edges are like 20 bevels.

It does it job, maybe one day I can have JPL or NASA mirror polish an exact convex edge.
 
Ankerson said:
The thing with a hollow grind is that you can have a thicker spine for added strenght and it can still slice well.
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Until you come up against that thicker spine in a full slicing cut and any added strength would mostly only be beneficial as a lateral pry bar.

This is one of those things that really matter what you are trying to cut and personally choice.
For a hunter to make shallow cuts through skin and meat a hollow grind works well and some swear by them. The Late Mr. Bob Loveless and his drop point hunter designs for instance. Some butcher knives are hollow as well.

For a Chef knife a full flat is the ticket for slicing veggies and will still shine as a meat cutter and plenty of hunters & camp knives are made with a FFG.

The Convex and Saber grinds will usually handle your chopping chores the best and as already noted you can put a convex edge on all three grind styles which is what I do.

There are also hybrid mixes of the three grinds as well.
 
It's worth noting that full-height hollow grinds exist, but aren't commonly seen because (unlike hollow saber grinds) they are very difficult to do right. The M.C. Cognet "Le Thiers" line is full-height hollow ground and cuts you just to look at 'em. The advantage afforded by the thick spine for rigidity must be balanced against the taper of the hollowing so you don't create a bad binding spot in the cut; as such it is best for hollow grinds to be subtle ones done using very large wheels (or ground against platens that mimic them.)
 
Some original Leatherman PSTs and the Kershaw 5250 are full-width hollow ground as well.
 
dannyp said:
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.
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I like the way you think dannyp.
 
Buck_110 said:
That combination hinders a hollow ground blade's slicing abilities. If the substrate being cut is taller than the blade is wide, the blade will bind. A thick spine adds no strength to the edge.
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It matters what you are cutting, meat will just move out of the way.
Carrots or apples, not so much.
Cardboard? Angle the blade so it pushes each half apart.

If you are chipping edges and breaking off points there are other problems at hand and it isn't the primary grind style.

There are hollow grinds and there are hollow grinds&#8230;







I honestly don't think there is a "best" only different.

I do, however, like a convex edge bevel on all the grinds.
 
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