Edge Geometry on Medieval Swords.

A swords edge is the whole point of its being. Sorry, we couldn't resist the pun, and it's the truth. The entire design of the sword blade, shape, dynamics, hilt form, and construction are all about creating a tool to deliver the edge and point of a sword to its target. In this post we lay out a few ways of considering the most desirable edge geometry for your sword. Given the increase in practice cutting with European swords, we thought the topic would be of interest.  

The edge of the sword is where the two planes of the blade meet. This can be a variety of shapes and angles depending on the intended use of the sword and the skill of the person who last worked on honing the edge. Most Medieval and Renaissance European swords are double edged and more or less laterally symmetrical. In this type of sword the planes that diverge from the thickest portion of the blade and taper down to the edge may be called the primary bevel. This bevel may begin at the central ridge of the sword, as in the diamond section blade below, or it may begin to the outside of a fuller or fullers, which is most easily seen in the narrow fuller example. This initial reduction in blade thickness as it approaches the edge is one of the primary factors that can influence a blades cutting ability as well as its durability.   


Blade cross sections

Simply put, the thinner the blade is in profile the more efficiently it will slice through a target. However, thinner blades are more easily damaged when they encounter an unyielding target. All of these different edge geometries and blade profiles are attempts at balancing a useful edge with a sufficiently sturdy blade to carry out its function. For example, a razor blade cuts very well, but if mounted on a pole and swung at a target it is unlikely to survive the encounter undamaged. Instead, it will bend or break, and the edge will chip or roll. This is why razors, while very sharp, do not make good edge geometries for swords.

The issue is of particular concern for swords, which are designed to deliver an effective attack with the edge or point against a target which may be armored or not. We are thus confronted with the reality that there is no “all around best” sword for all possible purposes. No all around best edge. No all around best blade.  Rather, a competent sword user of the period would have used the right tool for the job based on the perceived advantage of a particular style of fighting against a particular type of target, in a particular context if they have the choice. This is an important concept to grasp when studying the use of swords, as it explains some of the variation we see in sword edges. We need to allow the actual designs of period weapons to teach us the intended purpose and inform our interpretation of the techniques found in the manuals.  

When looking at the edge one must define what makes sharp, sharp. The edge of a sword blade is the meeting of two planes. The oblique angle at which these two planes come together dictates some basic physical constraints on how it will interact with another edge or target with which it comes in contact. Modern knives often utilize bevel grinds as part of the aesthetic of the blade, and there is a bit of a cult around what the very best edge angle might be. Many knives are ground to a 22.5% angle, which is sometimes referred to as “the most efficient edge bevel.” But simply reading any Internet forum on edge geometry and primary and secondary bevels will tell you that there is far from a consensus on the issue.


Primary and secondary bevel on a Swedish EKA knife

In terms of sharpness, the angle of the two planes coming together is not as important as the consistency of the two planes merging evenly with no flat, rounded, or rolled bit at the edge. A fairly thick blade can still be very sharp as long as the edge is finely honed and polished. The meeting of the two sides of the blade is most often a slightly convex shape. While some can be almost flat when made, as soon as the item has been sharpened a time or two, the convex shape will be there. If the blade faces are completely flat from center portion to edge the first time the edge is reduced it will become convex.  

As swordmakers we often strive to produce an edge with as small a secondary bevel as possible, because that seems to have been the most desirable way to sharpen in period, and because it preserves more of the thicker section of the blade closer to the edge, thereby making it more durable. This is particularly important when we recall that a blade used in combat will be aggressively contacting a variety of targets including other blades, textiles, rigid or chain armor, flesh, and bone. All of which will induce significant and different stresses on the blade. So, the blade needs to be sharp enough to hew through a limb, but sturdy enough not to lose that edge when it encounters other materials.

The image below is a link to a very high quality model of a German longsword from the mid/late 15th century.  You can observe millimeter scale detail on this original blade.  Zoom in on the edge.  It has no observable secondary bevel, yet it is still quite sharp, even after 500 years.  When compared to the modern knife above you will note a very different edge geometry that is both optimized for combat and a result of period technologies and aesthetics.

The edge of a sword blade also has zones that can be treated differently on some swords.  The point is the most obvious as this area of the blade can have several different configurations. The area just behind the point, for example, is often very sharp. This tip area can thus be used for slicing and cutting at the outer reach of the sword, or this area can be less sharp and more reinforced when it was seen primarily as reinforcing the tool for thrusting. The belly of the blade is where one will see the most wear and tear on the edge from use. This is the zone of the edge most people who practice cutting nowadays are using. This area can vary in sharpness on period swords, and it can vary from spot to spot on well-used blades.  So too, the forte of the blade can have a sharp edge all the way back to the guard, or can be less sharp and even rounded depending on the style and period of the sword.

The point, of course, is that the ideal sword edge for winning tatami cutting competitions may not be the ideal edge for fighting in the system that you train. Although we enjoy cutting tatami and recognize that it takes a great deal of skill to do well, we should also consider how optimizing a blade for tatami might be different from optimizing one for combat.  


divider swords

Nathan Clough, Ph.D. is Vice President of Arms and Armor and a member of the governing board of The Oakeshott Institute. He is a historical martial artist and a former university professor of cultural geography.  He has given presentations on historical arms at events including Longpoint and Combatcon, and presented scholarly papers at, among others, The International Congress on Medieval Studies.

Craig Johnson is the Production Manager of Arms and Armor and Secretary of The Oakeshott Institute. He has taught and published on the history of arms, armor and western martial arts for over 30 years. He has lectured at several schools and Universities, WMAW, HEMAC, 4W, and ICMS at Kalamazoo. His experiences include iron smelting, jousting, theatrical combat instruction and choreography, historical research, European martial arts and crafting weapons and armor since 1985.

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