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Blade Grinds


If you want to understand how and why blades are the way they are you need to study the blades made over the past thousand years. The surviving blades are those that worked for their users. These knives and swords were either flat ground or hollow ground; everything else is a variant of those two except the convex grind; which I will discuss below.

The grind on a blade lends itself towards different advantages and disadvantages. Some are stronger, others are sharper, and some try to find a balance of both. While each grind has its own strengths, the truth of the matter is that the width of the blade stock and the grind angles will affect the strengths of the blade much more dramatically than what type of grind is used. Everything I say below is wholly dependent on the grind angles and how thick the blade is. I will assume that the width and angles will be playing to the strengths of each of the grinds.

Blade Grinds Infographic - Full Flat grind, Hollow Grind, Sabre Grind, Chisel Grind, Convex Grind

 

The Hollow Grind

A. G. Russell 4-5⁄8" Titanium Framelock everydaycarry hollow ground drop point 9cr13mov

Full Hollow GrindTo make a hollow grind, the blade blank is applied to the surface of a grinding wheel or belt passing around a wheel. The depth of the hollow will depend on the circumference of the wheel. This means that many hollow grinds will be very shallow, and indeed on many blades it is difficult for the unpracticed eye to spot a hollow grind.

The hollow grind is popular for both production and handmade knives. This grind is easy to achieve on a machine - so production costs aren’t prohibitive (at least for this part of the knife).

The hollow grind is usually done on a thin blade, and then ground to have a thin edge. As I explained in my article on Blade Edges, thinner edges are a little weaker but they also slice better. Hollow ground blades are fantastic at slicing. If you combine a hollow grind with a nice deep belly, it will be one of the best slicing knives you have ever had.

The hollow grind does have disadvantages of course. The thinner edge can chip or roll over with hard use. They can also have difficulty cutting food due to the blade concave scoops. These hollowed out areas can sometimes create a suction, which makes deep cuts a little more difficult.

If you need your knife to be a supreme slicer, but you don’t need it to go too deep, the hollow grind will perform admirably. Dressing your game requires a knife that has exceptional slicing to remove the skin. Hollow grinds are common on hunting and skinning knives for this reason.

Another blade that uses the hollow grind is the straight razor. The extremely thin edge you can achieve with a hollow grind allows for easy push cutting with the straight razor.

Strengths: Fantastic slicing ability, easy to sharpen, easy to manufacture.

Best knife types: Skinners / Hunting Knives, Small to medium sized Everyday Carry blades, and Straight Razors.

Weaknesses: The edge does not hold up to hard use as well as the other grinds. Only average with deep cuts. No chopping.

 

The Full Flat Grind

AG Russell Folding Gents Hunter II 3-5/8" drop point blade 9cr13comov carbon fiber cobolo g-10

Full Flat grind pictureThe full flat grind is as it sounds - the grind goes all the way down from the spine to the edge bevel in a flat, linear slope. The flat grind is one of the most versatile grinds. It can be thick and heavy, or it can be extremely thin and sharp. Or it can be a balance between the two. Most flat grinds are a balance between the two, though it will depend on the design.

The full flat grind is thickest at the spine for strength, but tapers down into a relatively thin edge for excellent slicing. More steel is removed from the sides, allowing for easier slicing and allowing the blade to move through mediums easier. A full flat grind will (typically) be stronger than a hollow grind, and cut better than the sabre grind.

The flat grind’s primary bevel slopes linearly and slowly. This allows the full flat grind to pass through materials with more ease than other grinds who slope non-linearly (hollow), or at steeper angles (sabre). This is why the majority of kitchen knives are flat ground - so they can pass through food easily without much suction or resistance.

The full flat grind has a great mix of the strengths of the other two grinds. Because it is a great all-rounder, the full flat grind is one of the more popular grinds.

Strengths: Good cutting, strength, penetration, and chopping (depending on blade thickness).

Best Knife Types: EDC knives, kitchen knives, hunting knives. Honestly it is good on most knives.

Weaknesses: Doesn’t cut quite as well as a hollow grind, isn’t quite as robust as a sabre grind.

 

The Sabre Grind

Randall® Model 1 Fighter  with Black Micarta Handle
Sabre Grind pictureA sabre grind is either a flat or hollow grind where the primary bevel (the grind) covers about 50% of the width of the blade. Some believe that anything less than a full flat or hollow grind is a sabre grind. In my opinion, a sabre grind is ground about 50% and has a cut swedge at the top. So if someone says “sabre hollow ground” you know the blade has a hollow grind that starts partway down the blade.

The sabre grind is used when the maker wants a stronger blade. To make full use of the stronger blade, often the edge is also kept a little thicker so that the blade can stand up to hard use, such as chopping. With a thicker edge, the sabre grind will not slice as well as other grinds. Classic military designs such as the Randall #1 and the Ka-bar Combat Knife utilize the sabre grind.

Strengths: Excellent durability. It will hold up to chopping or penetration.

Best Knife Types: Military & Tactical Knives, Self-Defense blades, Camp Knives, Hatchets, axes.

Weaknesses: Its cutting ability is typically less impressive than other grind types.

 

 

The Chisel Grind

Ka-Bar® Becker Tac Tool
Chisel Grind ImageThe chisel grind is not ground on one side at all. It is completely flat on one side, and has the primary bevel on the other. The chisel grind may or may not have a secondary edge bevel. The knife pictured above, and the profile picture to the left, are both Sabre Chisel Grinds. You can see how the bevel starts partially down the blade. A Full Chisel Grind would have the bevel go all the way up to the spine.

The chisel grind is easy to make, as you only have to grind one side, and you don’t have to make the grind symmetrical with the other side. The chisel grind is also easy to sharpen for the same reason - there’s only one side to sharpen (and then strop off the burr). Because one side is left unaltered, the other side can be sharpened at a thinner angle, making for a thin, sharp edge.

Achieving accurate cuts is difficult with the chisel grind due to the unsymmetrical design. The blade will curve into the material being cut. So the knife will naturally slant towards the beveled side, causing the cut to be slanted as well.

Strengths: Excellent strength, good chopping (depending on angle), easy to sharpen, can have great cutting ability (again - angle).

Best Knife Types: Often found in choppers such as machetes or other bushcraft knives. Can also be found regularly in traditional Japanese Kitchen Knives.

Weaknesses: Can be very inaccurate, performance can vary widely - depending on grind angles.

 

The Convex Grind


Convex GrindThe convex grind was found on the knives made by early American blacksmiths with no understanding of the way knives were made by those who made a profession of knifemaking in their day. Convex “grinds” were easier to make with a hammer, which is why they were popular in those early days. Convex grinds have also been made popular by the followers of the Moran cult established by the writings of Ken Warner about his friend Bill Moran. Consequently, it is also known as the Moran grind.

The convex grind arcs down into a convex curve (arcs out) towards the edge. The convex grind is similar to the sabre grind in that it (typically) still has a lot of steel in the middle of the blade. This puts extra steel behind the edge, reinforcing and strengthening it. Unlike many of the other grinds, the convex grind does not use a secondary edge bevel, instead moving into the edge from the arc.

Nowadays, a slack flat belt grinder is used to make the convex grind. The main drawback of the convex grind is that it is difficult to sharpen. The best way to sharpen a convex grind is with a flat belt grinder - which most people don’t have (and for good reason). An alternative method is to take something flat with a little give, such as a thick mouse pad, and put some sandpaper on it and use backward strokes (away from the edge) on the knife to sharpen it up. You’ll of course need to go through several grits of sandpaper to bring the knife back up to sharp. Afterward you’ll need to strop off any burrs since you are using the backward stroke method.

The convex grind is widely used with axes, and sometimes with machetes. Bolos and Kukris often use the convex grind as well. The thick edge can take a beating without chipping or rolling. In traditional axes such as the Gransfors, a hardened piece of steel is forged into the edge, while a softer steel forms the backend of an axe, allowing it to more easily absorb forceful strikes.

Note that most choppers do not use the convex grind. You can get similar strength with a wide angle on an edge bevel.

In my opinion, the convex grind is useful only in large chopping blades and axe formats. I do not think the convex grind is useful in smaller knife formats. There are some who disagree with me. You will have to come to your own conclusion about it.

Strengths: Very strong edge, great for chopping.

Best Knife Types: Choppers, Machetes, Axes, some larger bushcraft knives.

Weaknesses: Difficult to maintain and sharpen - requires skill, and uncommon sharpening tools. Can have difficulty carving, not the greatest slicer. Performance can vary wildly depending on angles.

 

The Dual-Ground American Reinforced Tanto

CRKT Amicus Compact Jesper Voxnaes Denmark designed, rugged outdoor knife, 8cr13mov, black g-10
The American Style Tanto combines two grinds. Along the flat section of the edge, the blade is often sabre hollow ground. This gives the blade a thin, sharp edge. Along the front of the blade by the point, the grind changes to a flat/sabre grind. This gives the tip incredible strength. The result is a sharp bottom edge with a strong tip - allowing for strong penetration. Of course this strengthened tip does not pierce as easily, but it will not easily break either.

I, myself, am not overly fond of the American Tanto for my personal use. It can look intimidating, and for that reason is it popular with the younger generations. The American Tanto can be difficult to sharpen the two different grinds and get all the angles correct - many have difficulty with the transition between the two grinds.

Strengths: Strong point - won’t break easily, great cutting ability along the flat of the edge.

Weaknesses: Doesn’t pierce softer targets as smoothly as other grinds due to the extra steel at the point. Can be difficult to sharpen.

 

The Scandi Grind

The Scandinavian grind, or Scandi grind, is a short, flat or hollow grind on a thin blade where the primary grind is also the edge bevel.

The benefit to using a Scandi grind is that you can use the entire primary bevel to guide your knife along the bench stone as you sharpen it. Just put slightly more pressure on the very edge to form a miniscule edge bevel (it won’t really be visible). Of course, for this to be a benefit you have to use bench stones as your sharpening device.

I do not recommend turning your knife with an edge bevel into a Scandi grind. If the maker designed the knife to have an edge bevel, than turning it into a Scandi grind will often make the blade too thin and will have a weak edge. Only use the Scandi grind if the knife originally came with a Scandi grind.

 

Conclusion

The conclusion is different grinds work for different jobs. If you are looking to pick out a blade, think of what you’ll be doing the most to get an idea of which grind is best for you. If you aren’t sure, drop us a line on our Facebook page. We’d love to talk it over with you.

 

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