| Knife Blade Geometrics Handy Niknaks | | | | Spyderco Knives 'Spyderedge' is a secondary |
| There are many geometrical variations of blade | | | | bevel, ground on one side of the blade only and |
| thickness, blade point, belly, spine, edge angle and | | | | may be re-sharpened using the pointed angles of |
| grind and each variation has trade offs between | | | | ceramic sharpening stones. |
| cutting ability and strength. | | | | Some of the blade shapes in popular use are |
| The belly of the blade is the curving portion under | | | | outlined below: |
| the point which may be absent in Tanto or | | | | Recurved Blade |
| Sheepfoot blades. Blades with more belly are | | | | The belly of the knife is ‘S’ shaped and |
| optimised for slicing rather than piercing. An | | | | presents a greater edge length to the material |
| optimal piercing blade with a strong and easily | | | | being cut. Although ideal for slicing, recurved |
| controlled tip may have little or no belly, being less | | | | blades are almost impossible to re-sharpen |
| useful for slicing. | | | | without specialised equipment. |
| The angle between the edge and the handle plays | | | | Sheepsfoot Blade Shape |
| an important part in the knife ergonomics. The | | | | Sheepsfoot blades do not have a point, as the |
| edge may not be parallel to the spine of the knife | | | | spine curves down to meet the edge and these |
| and may have a positive or negative included | | | | are often used in rescue knives. Emergency |
| angle. A positive angle provides more belly and | | | | procedures may involve cutting through a |
| edge, whereas a negative angle provides a | | | | jammed seat belt in the aftermath of a car crash. |
| sharper point. A variation of this is when the blade | | | | Clothing may also have to be cut through in order |
| and handle are joined at an angle to further | | | | to free a victim or to gain venous access. Cutting |
| enhance slicing ability. | | | | through fibrous materials in such close proximity |
| The point of the blade is strongest in the Tanto | | | | to the casualty is much safer if the knife being |
| design, as the spine is full thickness all the way to | | | | used does not have a sharp point. |
| the point. For a sharp point, the steel needs to be | | | | Clip Point Blade Shape |
| as thin as possible such as in the dagger blade. For | | | | The tip is formed by a concave or straight cut |
| maximum control of the point, the point of the | | | | out portion of the blade spine which is the 'clip'. |
| knife should be in line with the user's hand, below | | | | The upper false edge usually has a bevel, making |
| the level of the spine of the blade. | | | | the point sharper. The point of the blade is |
| The thickness of the blade alters the strength and | | | | lowered bringing it closer to the midline of the |
| cutting ability. The objective is to have as fine an | | | | blade. The Buck Ranger B112 Model features the |
| edge as possible, yet maintain the strength of the | | | | clip point with a bevelled, concave false edge on |
| edge and the blade in general. Different types of | | | | the back of the blade tip. |
| grind may be applied to the blade. A flat grind will | | | | Drop Point Blade |
| maintain the strength of a thin blade, whereas a | | | | The tip of the blade is lowered by a convex, |
| hollow grind will provide a thin edge in a thick | | | | unsharpened curve of the blade spine, providing a |
| blade. The combination used depends on the | | | | stronger, though less sharp tip. The Spyderco UK |
| function of the knife, whether intended for fine | | | | Penknife C94GP has a full flat grind drop point |
| delicate cutting, or for heavy weight chopping and | | | | blade with a secondary bevel of 20 degrees on |
| levering. | | | | each side of the edge. In some cases, a portion |
| The edge thickness is determined by the | | | | of the blade spine near the tip may be ground |
| thickness of the blade spine, the blade shape and | | | | off, creating a 'Swedge' or unsharpened false |
| the grind type. The primary bevel may be flat, | | | | edge. This removes weight from the blade, |
| hollow, convex, chisel or sabre ground. The cutting | | | | improving balance and penetrative properties. The |
| edge is formed by a secondary bevel and this | | | | Spyderco Police C07 Model has this type of |
| may be altered by the knife owner by | | | | weight reducing swedge near the blade tip. With a |
| re-sharpening, to provide a thinner or thicker | | | | 3 mm thick spine, the hollow grind primary bevel |
| edge. | | | | gives a relatively thin cutting edge. |
| The hollow grind blade has a biconcave cross | | | | Tanto Blade |
| section and has the advantage of a very thin | | | | The tip of the blade is in line with the blade spine. |
| edge which is easy to re-sharpen. | | | | The sharpened front edge meets the long edge |
| The chisel grind edge is ground on one side only, | | | | at an acute angle, forming a second point where |
| with single sided bevels. Re-sharpening only needs | | | | the two edge join. This creates an incredibly |
| to be performed on the bevelled side of the | | | | strong point, as the blade spine is full width until |
| blade, with simple burr removal on the un-bevelled | | | | very close to the point. |
| side. This provides a thin, strong edge which is | | | | Spear Point |
| easy to maintain, although it is inaccurate when | | | | The point is located at the midline of the blade |
| cutting due to the assymmetry of the edge. | | | | and the blade spine may be sharpened on both |
| The Sabre Grind edge has a flat primary bevel | | | | sides near the tip. |
| starting near the middle of the blade which gives | | | | Trailing point |
| a strong edge for chopping and hard use. | | | | The point is the same height or higher than the |
| The Flat grind has a V-shaped cross section, is | | | | spine of the blade, providing an enlarged blade |
| stronger than a hollow grind, though less strong | | | | belly for slicing or skinning. |
| than a sabre grind. The Spyderco Military Lock | | | | Hook Blade |
| Knife C36 has a 4mm thick blade spine and full | | | | A concave shaped blade found in pruning knives, |
| flat grind primary bevel, with 20 degree | | | | marine and rescue knives. Cutting is improved by |
| secondary bevels on each side. | | | | starting the cut at the edge near the handle and |
| The convex grind has a biconvex cross section, | | | | pulling the knife inwards, thus forcing the material |
| without a secondary bevel and is formed using a | | | | being cut closer to the edge near the tip. |
| flat belt grinder. This produces a blade with a | | | | Dagger Blade |
| strong point and strong edge although the bevel | | | | Tapers to a thin, sharp point, with both edges |
| cannot be easily changed. | | | | sharpened and ground in from the exact midline |
| Serrated Edge Blades | | | | of the blade. |
| A serrated edge increases the effective cutting | | | | Blade Steels |
| edge length by up to 24%. The sharpened | | | | The type of steel used determines the |
| recesssed curve has more linear cutting surface | | | | toughness, edge holding ability, corrosion |
| than a straight edge. Edge retention is also | | | | resistance and ability to resharpen the blade. Steel |
| greater because cutting is started by the | | | | with low carbon content has a higher resistance |
| serrations' tips, easing the workload on the | | | | to corrosion, whereas high carbon content |
| recessed edges, and protecting the sharp inside | | | | provides greater toughness and easier |
| cutting curves which wear less over time. | | | | re-sharpening. |