Flatground knives vs others

[Fanis]

Some knife manufacrurers (like Busse) prefer flatground blades while others (like Strider) use other blade styles. Are flatground blades stronger than other kinds of blades? Could anybody explain the advantages and disadvantages of flatground blades? What style gives the strongest blade given the same blade thickness?
Thank you in advance,
Fanis

 

[Crayola]

Hello, and welcome to the forums. I'd recomend first of all that you check the FAQ section here. I think Joe Talmadge wrote about blade geometry there.

But to answer your question here' I offer the following:

Generally speaking, a hollow grind will outslice the other grinds, but it is the weakest. A convex grind is the stringest, but the poorest slicer. A Flat ground blade is a compromise.

Incidentally, Busse doesn't use flat grinds, but one side is flat ground and the other is convexly ground. Strider uses hollow grinds, but they are switching to flat grinds.

Deciding on which grind is best depends on your usage and materials. For example, if you do a lot of light cutting (string, envelopes, boxes, etc.) a hollow ground blade of thin stock would be great. If youa re goinf to be chopping or taking your blade into combat, a more shallow ground hollow grind or a flat grind would be better.

It also depends on what you are cutting. A hollwo grind can catch on thick mateiral you cut. Flat ground kitchen blades work great as there is no hollow for material to get hung up on.

Good Luck!

 

[rdangerer]

Originally posted by Crayola
Incidentally, Busse doesn't use flat grinds, but one side is flat ground and the other is convexly ground.

To be clear, the recent Busse stuff typically has a full flat ground blade... the final edge is flat on one side, and is a convex final edge bevel on the other side. I'm really guessing here on how actually produced, but would guess the flat beveled edge is done on a stone or a flat platen-backed belt grinder, and the convex side is done on a slack belt on a belt grinder.

Convex edges are harder to sharpen (slack belt, soft backed sandpaper, etc), but can be made hair poppin with practice.

Convex edges excel on large blades that will be used for chopping. Convex tends to not stick/wedge as much as flat and certainly not as much as hollow for such tasks. The Convex edge is stronger vs. flat and noticeably stronger vs hollow simply because the edge deforms less readily as it's backed up by more metal.

Fully convex grinds are rare.... Moran did some, I think of the classic Scagel camp knife when I think of full convex grind.

Usually the custom makers who do "convex" actually grind flat and then convex the final edge bevel on a slack belt, or they grind flat for 3/4 of the blade height and then do say the final 1/4 of the blade in a convex grind. (ABS Bowies are often done this way).

The recent Fallkniven production (F1 at least, may be others) is a full flat grind with a very nice convex final edge. In this case, the blade height is 1-1/8". About the last 3/16" of an inch of blade height is done convex on mine.

 

[bensano]

My Marble's mini-caper is convex from edge to spine.

 

[Steelwolf]

The Himalayan Imports Khukris are all convex edged. Many axes are ground with a convex edge too. Recommended for chopping.

I wouldn't really say that flat ground is easier to sharpen. If you do free hand sharpening on a stone and don't pay attention to what you're doing, you can quickly end up with an uneven convex edge.

But the flat ground is still the best compromise between edge strength and slicing ability.

 

[Fanis]

Thank you very much for the information. I still have one more question. When we have to use the knife for prying, isn’t hollow grind stronger? A hollow grind blade keeps the maximum thickness over a larger part of itself while the flat grind has the maximum thickness only along the spine. As an example, I would like to compare the Combat Grade Busse Natural Outlaw and the Zero Tolerance Busse Natural Outlaw. If both blades had the same thickness, wouldn’t Zero Tolerance be a stronger blade than the Combat Grade one? Please excuse me if what I am asking looks like nonsense but I am new not only in the Forums but to knifes anyway.

 

[Cliff Stamp]

Some comments on the properties of the various grinds :

http://www.bladeforums.com/forums/showthread.php?s=&threadid=171079

Fanis :

A hollow grind blade keeps the maximum thickness over a larger part of itself while the flat grind has the maximum thickness only along the spine.

Yes, a *sabre* ground hollow blade can be stronger than a *fully* flat ground blade of the same stock if the sabre grind on the hollow ground blade is shallow enough. The strength difference here is due to the difference in the height of the grinds more so than the nature of grinds themselves. Note that a very shallow hollow ground blade will suffer a significant loss in cutting ability because of the shallow primary grind and will also wedge badly.

Note some Busse blades are now fully flat ground will a smooth transtion to a convex edge, no distinct secondary bevel is visible. The regular combat line has flat primary bevels and a dual edge consisting of one flat and one convex bevel.

-Cliff