Survival Knives: Blade Design
There are thousands of blade designs – wandering through a well-stocked knife shop or website can be bewildering. The design of a blade is supposed to be the result of intended function. It’s ‘supposed’ because with knives as other things, form doesn’t always follow function.
Sometimes aesthetics or custom is at work, for example, in the so-called blood groove (a fuller or cannelure), which is meant to channel blood from a hunting or skinning blade, but is sometimes added to other types of knives for appearance. Other times, it’s the marketing department, which believes that this cool pocket knives with wicked looking serrations on the knife make it more likely to appeal to a certain kind of customer.
Fortunately, for survival knives there are two bedrock design qualities – versatility and strength. Looking at the aspects of blade design, we’ll keep in mind these two qualities and how they influence blade design selection.
Length – As mentioned elsewhere, a prime characteristic of a survival knife is a full tang, meaning that the blade steel extends, at more or less the same width and thickness, all the way from the point to the butt.
This being the case, the length of a survival knife is blade length plus the tang. Among knife aficionados, you can always get an argument about the optimum blade design length, but the most common recommendations are a blade length between 4 and 10 inches.
Lean shorter if you’re idea of a survival knife includes more fine cutting (such as whittling or skinning) or longer if batoning wood is more likely. The handle should be long enough to comfortably fit your hand. Keep in mind; any knife with a total length around 12 inches or more may begin to be a problem for wearing and handling.
Thickness – While not the only factor (see the article Survival Knives 101: Blade steel), the thickness of the blade design is obviously critical to the strength of the knife. Of course, in general, the thicker the blade, the stronger but the trade-off is weight.
Most survival knives are in the range of 5/32” to 1/4″ (4-6.35mm, 0.1563”- 0.2500”), with the emphasis on the thicker end. Thickness as a factor varies a great deal among manufacturers.
Blade Design: Point Type
For a survival knife, the point (or tip) needs to be sharp enough to penetrate tough surfaces, even leather, strong enough not to break when used for prying and tough enough to resist serious wear in uses such as digging.
This usually means the points of most survival knives favor thicker designs. There are many blade point designs and with each almost unlimited variations; here are four of the most common:
- Drop-Point – This point features a gradual and convex curve that drops from the spine to the point. It’s probably the most common design for survival knives because of its strength and ease of sheathing.
- Clip-Point – The reverse of the drop point, where the curve is concave from the spine to point like metal was ‘clipped’ out of the blade. This is a common design for survival blades.
- Spear-Point – Like the name says, designed for spearing, with symmetrical convex curves from spine and belly. Since spearing is just one of dozens survival knife uses, this point is specialized.
- Tanto-Point – Points of this kind have many variations but all feature one or more straight edges to the point. The design is optimized for fighting and tactical uses.
Blade Design: Edge Type
Like all knives, a survival knife has two edges: spine and cutting, but the spine edge is almost never sharpened. In fact, the spine edge for survival knives should be flattened (squared-off) for a better striking surface.
For the most part, the cutting edge is what a knife is about, so it’s worth understanding a bit of detail when looking at survival knife edges.
Straight – A smooth cutting, which isn’t necessarily “straight” as it usually has curves, especially a belly.
Partially Serrated – A portion of the blade design near the handle may have serrations or scallops.
Serrated – The saw teeth design on blades tends to be a very controversial subject. The majority of survival knife experts don’t recommend serrations on the knife, either on the spine or on the cutting edge. Then why do so many models of survival knives have serrations of one kind or another?
Serrations can cut things, mostly fibrous things like ropes and straps, which are difficult for a straight edge.They also suggest wood sawing, but in practice – not so much. But then serrations look wicked. Other than that, serrations usually require a special tool to sharpen, tend to clog when chopping, and unless well integrated into the blade design, may weaken the knife.
Blade Design: Grind
When sharpening the cutting edge, the shape or pattern of the edge needs to be maintained by the grind. There are some common grind patterns. You’ll see all of them or their variations on survival knives but one combines excellent sharpness with strength and reasonably easy sharpening:
- Hollow – made with two concave scoops, it leaves a very thin ridge at the center of the edge. This is an extremely sharp grind, often used for razor blades and skinning knives, but also relatively fragile. Hollow grind is very uncommon on survival knives.
- Full Convex – the taper to the edge is a convex curve instead of straight (sort of the reverse of the hollow grind). This leaves a lot of metal just behind the edge, adding strength. It’s often used in axe blades and works well in survival knives for splitting, however, the convex curve requires skill to maintain.
- Full Flat – features a straight taper from spine to edge. It can make a very sharp edge but it’s less durable and harder to maintain the grind.
- High Flat – like the full flat grind, it’s a straight taper to the edge but it begins further down the blade, leaving more metal to back the edge. This grind usually has a second grind, or bevel, near the edge. Control of the second grind is difficult by hand.
- Scandinavian or Sabre – this is another straight taper grind, like the full flat, but it begins much further down the blade, usually at half or beyond. It has the metal support of a convex grind, almost the sharpness of the full flat grind, and because the only sharpening requirement is to keep the bevel straight, relatively easy to sharpen in the field. This is the grind used on the majority of survival knives.
Blade Design: Belly – This is the curvy portion of the cutting edge on the blade design. On some knives, especially those used for skinning, the belly can be pronounced and often accompanied with a trailing point design, which means the point is higher than the spine. This design can make for some good-looking curves, but not for strong points or easy sharpening. The belly on most survival knives is modest to non-existent.
There are a couple other parts to some blades, which you’ll see on survival knives. A ricasso is the unsharpened thickening of the blade just before it enters the handle. If done well, it can add to the strength of the knife at a particularly vulnerable point.
In roughly the same section of the knife as a ricasso, but on the cutting edge there might be a choil, an unsharpened indentation or finger sized cutout. This is useful for controlling the knife in whittling or butchery.
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