question re: different grind types

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uncleknife

Joined
May 25, 2000
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Are different blade grinds better for certain applications or materials?

As example, are convex blade grinds better for cutting meat, flat grids for ??? or hollow grinds for ????
 
There are really six different basic types of grinds commonly used in knife making. Note. I'm not talking about blade shapes. For example: A Tanto is a blades design and a tanto blade can use a number of different grinds for the edge. The blade design is a whole different matter and whether it be a clip point, clip point with thumb cut out, swedged clip point, drop point hunter, upswept skinner,upswept skinner with thumb cut out, tanto or modified tanto, dagger with single edge, double edge dagger, dagger with false edge, gut hook, or Wharncliff design it can be made to use one of any number of these grinds.

The common grinds seen are:

Flat Or V grinds- Good for skinning and carving. Above average slicing ability, good edge holding ability but not too resistant to abuses.

Modified V- Perhaps the best grind for general purpose campground uses. A bit harder to hone with only fair slicing ability, but great resistance to abuses and a very strong edge due to the thickness of the grind.

Modified V with fullers (AKA Blood grooves)-I believe Ka-Bar developed this grind. At least that is the first palce I ever saw it in an old Marine Corp. knife. Basically the same grind as the modified V with less weight thanks to the fullers, and perhaps not as resistant to as much abuses as a Mod V due to less spine from the metal removed to make the grooves or fullers.

Concave- Very similar to the hollow grind but this grind covers the entire blade. This grind has apparently died off as very few makers utilize it anymore. It offers great slicing but poor resistance to abuse due to it's inherent thinness. Hitting a bone or knicking the blade can chip it easily. Using it as a pry bar could be disastrous. It is perhaps the easiest of all grinds to sharpen though, but the edge life isn't great due to the thinness so you'd be doing it a lot.

Hollow- This grind is the grind that replaced the concave grinds of earlier times. It offers the same excellent cutting and slicing ability of the concave grind but has a bit more strength due to the thicker spine behind the edge. Edge holding is better than the concave usually depending on steel used, the width of the hollow ground portion of the blade and the thickness. Resistance to abuse is only slightly better than the concave grinds but it is better.

Convex-This grind offers great resistance to abuse and long edge holding life is to be expected in this grind due to the strength and thickness of the blade and the edge. Mostly used on tools designed for chopping and hacking. It is harder to hone this grind and on the heavier tools utilizing this grind like axes and hatchets it is usually done with a file or a very course stone. Slicing is poor on this grind so carving or slicing wood, debarking trees, or cutting meat is out of the question unless you are using it to chop off chicken heads or cut through bone in one chop like in a cleaver. I use an old Marbles convex knife for breaking through the breast plate of the white tail I bag just about every year.
 
All of the grinds mentioned are able to perform mostly any cutting task. Generally speaking, the flat grind is most common for kitchen duty but any of the other grinds will also work. I've butchered entire deer with a convex grind knife. From field dressing to skinning to cutting it into steaks and roasts. It can be done although I feel the flat grind for kitchen duties would be a better choice. Hollow grinds and flat grinds, depending on how thin they are ground, have more of a chance of chipping out on the edge with heavy use then the convex grind. All that is necessary to maintain the edge of a convex grind is to simply strop REGULARLY. If this is practiced you'll will have a blade that is very easy to maintain.
Scott
 
I like a tall flat grind. You can always put a convex edge on it if you want but its hard to put a flat grind on the knife later.

On one knife I made I had a flat grind up untill the sweet spot for chopping where it was changed to a thicker convex grind. Sort of a multi function camp knife. Wish I still had that puppy. Chopped wood and kept on shaving......
 
I would also add chisel grind to the list of common grinds because, well because its fairly common.

I always called the convex grind an "axe grind". Has anyone else heard this term for convex grinds? I'm wondering if it's a common term or just "a New England thing".
 
I'm a little confused as to how any of you guys think you can miraculously put a convex grind on a knife that has been flat ground. The only way to do this would be to add steel back into the knife somehow to replace what was ground away to make it a flat grind.

You could turn a convex ground knife into a flat grind if you wanted, or you could turn a convex into a hollow grind or a concave or a modified V or modified V with fullers. But once the steel is removed you can't go back to a convex...ever. Grinds like described above are not the bevel of the cutting edge. We are talking about the grind of the entire cutting portion of the knife of which the bevel is then attacthed to. Think of it this way. Convex= pot belly. Rounded out away from the center. To make it concave you would have to take away that rounded out part of the steel. Once it is gone it is gone.
 
STR - You can take a flat ground knife and create a convex grind. You will sacrifice some of the edge and loose a little in the dimentions. The final blade wont be what it was....I think it would be ruined but it depends on what dimensions you have to start with. I wouldnt regrind a flatgrind if it were me. I was simply saying that alot of knives have a flat grind with a convex edge. Seems to me if the sides of the grind get in the way of a deep cut its pointless. I dont think I helped much but thats my .02.
 
It's a convex EDGE, not grind. I could take a hollowground and convex the edge so there is no shoulder
 
You are talking about the edge. That is not the grind. The original post asked about the different grinds. You are mixing up the two. Once a knife grind is hollow or flat it cannot be made convex. There is no way that is physically possible.
 
STR said:
You are talking about the edge. That is not the grind. The original post asked about the different grinds. You are mixing up the two. Once a knife grind is hollow or flat it cannot be made convex. There is no way that is physically possible.
Click to expand...

With respect, no; not impossible. Just impractical because of the amount of steel you would have to remove, leaving much less width. It is practical to convex the edge, which has many of the same benefits: more steel to support an otherwise quite acute edge profile.


"Ka-Bar":

If a fuller is put above the edge 1/8" or so, you have the Marble's Ideal. The idea is to reduce drag when slicing. A sort of "semi-hollow ground" edge. The "Ka-Bar" was supposed to be a version of the Ideal, but the designer was ignorant of the principle behind the Ideal and put the fuller too high to have the effect of reducing drag in slicing.

"Axe Grind":

I have also heard convex grind referred to as a axe grind, and I have a couple of axes whose grind could only be called "convex." Not all of my axes are ground that way. Some (GB's) are more concave grinds with convex edges.
 
Putting a convex edge on a flat grind blade will enhance edge strength. The type of edge has nothing to do with the grind. The grind and edge work hand in hand giving a blade it's ability to cut. The convex edge is stronger because it allows more thickness at the edge. A thin flat edge is good for light to moderate pressure cutting. A convex edge allows you more in the way of force when cutting. IMO, match a convex grind and a convex edge and you have a powerhouse.
Scott
 
Actually the idea of fullers in a blade was not for blood grooves or for slicing efficiency. It is generally thought that it was simply to reduce the weight of the blade and increase strength on a weapon carried in combat situations.

The end result pretty much produced a knife that did all four things. What company invented it is still highly debated. Most likely this technique was not invented by a modern day company or individual. Old 18th and 19th century calvary sabres utilized fullers long before Marbles or Ka-Bar was even concieved of. Who utilized them in knives first is debateable. I thought Ka-Bar did in the Marine fighting and survival knife.

In the old days fullers were not ground out like they are in most cases today. Ground out fullers actually weaken the blade along the spine as well as reduce weight. (apparently they work to allow a channel for blood to flow as well)

Swords and Sabres that were hand forged in the earlier times were made using a pipe along the spine of the blade to increase it's strength. As the 19th century progressed and metallurgy improved, pipe backs were no longer necessary to increase the spine strength of a sword or sabre. They gave way to grooves forged in the side of the sword and these were known as "fullers". Fullers were made by first heating up the blade to make it malable and then by positioning the blade over a bottom fuller mold, (or positive impression mold that came in various lengths and widths and degrees of curves) setting a like sized top fuller mold on the top side of the sword, and hitting the top fuller with a hammer sharply, sometimes more than once. What happened was that the fibers of the metal would spread out thinning in one spot and squeezing together in others. Besides making the sword lighter, the fullers made it more flexible and stronger along the spine as well as, less likely to snap under the extreme stresses of battle.


There is no way to replace steel into the blade once it is ground away period! You can indeed round the edge on any grind regardless but that is redundant to say the least. To do so would reduce the efficiency of the cutting edge in a concave, flat or hollow ground blade or any grind type of blade to the point that one would have to question why even do that? Hollow and flat grinds were ground out that way to make them an effective and effortless slicer.

In my mind there is no strength benefit to a rounded edge on a flat or hollow ground blade and in fact it could be argued that it would demand increased pressure on the spine to make the knife with a rounded edge cut as it used to before the edge was rounded, which inadvertantly would result in making the knife a liability.

Sharp knives are safer than rounded off dull ones. More pressure on the blade equals more force when it slips and that equals deeper more severe wounds if it cuts into the user or bystander. Sharper blades are easier to control and require less force to make them work, thus they are safer.

Convex grinds were invented for heavy chopping instruments like cleavers, and machetes, axes and hatchets. The edge on these grinds is supposed to be rounded. That is what increases the strength and edge holding ability for what it was designed to do. The very design prohibits a convex grind from ever giving the user the same kind of control one of the more effective grinds can offer. And while it may be true that a convex grind can be seen on smaller knives and that they can be made to do the jobs of other grinds on a smaller knife the fact is the grind was originally created for the heavier implements..


See more here at the link below and you will see why I contend that making a concave, hollow or flat grind knife blade into a convex grind is physically impossible. As I said you could certainly take a convex axe, or even a modified V axe and hollow grind it or flat grind it but you cannot physically ever go back to the original convex or mod v grind once you remove the metal from the belly of the cutting edge. Not unless you perform a hands on healing of the blade and replace the steel you ground out of it.
http://www.atar.com/index.php?module=pagemaster&PAGE_user_op=view_page&PAGE_id=3&MMN_position=3:3
 
I think what blgoode meant in his post was not making a flat grind a convex grind but putting a convex edge on a flat grind blade. Forgive me blgoode if I'm wrong to assume this. It's true once the material is gone you can't replace it but you can put a convex edge on a flat grind, I know I do it. As a matter of fact you can put a convex edge on any grind type.
Scott
 
Getting back to the original question I believe the most usefull grind is the flat grind esp in the kitchen. The hollow grind is esp. useful where a razor edge is needed on skinning knives, craft knives etc. The Sabre Grind is akin to the hollow grind in many ways. As far as the Convex grind is concerned I believe the jury is still out except where a "chopping" edge is needed.
 
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