Mission Knives: Serrated Edge Analysis by Rick Schultz

SERRATED EDGE ANALYSIS
by RICHARD SCHULTZ and DENNIS STEELE,
Introduction by Mr. SAL GLESSER of Spyderco Knives.

INTRODUCTION
This article analyzes the serrated edge, and tries to determine the how's and why's of a serrations' performance. Also discussed are the things that serrations will outcut and outperform a straight knife edge. In the conclusion of this article, the authors recommend the best all around knife. Since this is an article primarily on and about serrations, we wanted a good introduction that summarizes the history, testing, and evaluation of modern serrations . . . and who better to do this than Mr. Sal Glesser of Spyderco Knives . . . Mr. Sal Glesser - Our interest in serrations developed during the 1970's when we learned that a serrated edge cuts more effectively. Investigation at that time revealed that they cut more effectively for a variety of reasons;
You have more linear inches of cutting surface, You have single point penetration at the tip of each serration. The concentration of force at the tip provides much better penetration than just sliding a sharp plain edge across almost any type of material, The center of effort rotates around the serration as you are cutting with it. This permits a more efficient separation of the material being cut.
In experimenting, we also learned that the shape of the serration, size of serration and angle of the grind within the serration has significant effects. We have also found a few things that serrations don't do nearly as well as plain edges. That would include carving, whittling, some skinning applications, the cutting of certain foods, and scraping. Some of the advantages of the serrated edges would be on a cutting board for example. The tip of the tooth is the only part that hits the cutting board. The recessed edge is hitting only the softer food and is likely to stay sharper 5 - 10 times longer than the same knife in a plain edge used on the same cutting board. We also found that if you have a very good steel (by good I mean hard and tough), the serrated edge can be used to cut materials that are much more difficult. For example, a number of our customers have actually used the serrated edge to saw through steel cable. The serration allowed the actual cutting of the cable through the stepping of the serration. That would not have been possible with a plain edged knife. Naturally the steel in the blade has to be extraordinary and considerably harder than the cable that was cut. In each case, it did ruin the knife but it does give an example for the potential of a serration. We also found that a serration can be used to make a very poor quality steel appear to be much more effective. Some people refer to a serration as a saw tooth. This is not entirely true. A saw tooth does not have a sharp edge between the teeth; the actual tooth is the sharp edge and it is doing the cutting. With a serrated edge, you have a sharpened edge between the tip of the teeth so that constant cutting occurs. The combination edge seems to be very popular with many customers. The attitude is that it has the best of both worlds. I'm still not sure if that would work for me as I personally prefer more teeth and less plain edge. I like only enough plain edge to do that scraping or fine cutting that would be necessary, but this is a matter of preference.
II. SERRATIONS ANALYSIS - Richard Schultz and Dennis Steele
Mr. Glesser makes some good points (no pun intended), and the authors would like to explore each of these further. Serrated edges, like straight edges, have their place in the cutlery industry. First, a few terms will need to be defined to help explain the differences between a serrated edge and a straight edge.
Terms:
Slicing - Consider straight edges to slice through material. Slicing can be defined as a clean or uninterrupted cut. Examples would be slicing open an envelope, and slicing a paper-thin piece of roast beef. When analyzed, the material would show a smooth separation with very little, if any, material being removed by the slicing action. Cutting - Consider serrations to cut through material. Cutting can be defined as an aggressive separation of material. Examples would be cutting through a multi-braided nylon rope, and cutting through electrical cable. When analyzed, the material would show a somewhat jagged separation with some material being removed by the cutting action. Sides of a knife - The right side of the knife is defined to be on your right as you hold the knife in your hand in the normal cutting position, point away from body, cutting edge down. The left side is just the opposite.
Advantages:
Industry analysis has shown that serrations provide the following advantages, which we will discuss further: Serrations cut more aggressively than the straight knife edge "Scallops" stay sharp longer than the straight knife edge The authors believe that if you are right handed, the serrations should be on the right side of the knife, and, if you are left handed, the opposite is true. Most cutting is done by pushing the knife away from you. Not only can you exert more force this way by using stronger muscle groups (push = chest, shoulders, and triceps, pull = back and biceps), but it is much safer if the knife slips. When cutting with a serrated blade, the knife edge will want to "roll away" from the serrations. When using a knife with the serrations on the right side of the blade - if you are right-handed , the knife edge will want to "roll left" while your arm extension will want to naturally turn your hand, and ultimately, the knife edge to the right. These two factors give you a straighter and more controlled cut. What this ultimately accomplishes is that the user will be able to apply more pressure into the cutting action without wasting energy into sub-contiously correcting and adjusting the cutting angle. Another factor that makes serrations cut more aggressively than a straight edge is accomplished by the physics of the serrations themselves. As less knife blade metal is coming into contact with the material being cut (i.e., the tips of the serrations), the more pressure that is being directly applied at that point. In other words, when exerting the same pounds-per-square-inch to the knife over a smaller contact area, the pressure at the blade edge contact point directly increases.
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