Tuesday, March 1, 2011

Folding Knife Scoring System

Numbers have always intrigued me. Statistics are the siren’s song for baseball fans. I also grew up on a steady diet of EGM’s Review Crew. Their 1-10 scoring method worked so well and was so intuitive that I thought about all media, not just video games in that way.

So I decided to create a numerical scoring system for folding knives. The purpose is not to try to make objective what is largely subjective, but to create a way of comparing knives in a single system. I am not saying my score is the only possible way to evaluate a given knife, but that it allows comparisons between knives. Hopefully it will also allow me to look at knives systematically.

Additionally, all of the scores are use-specific. That is, a Zero Tolerance or Emerson knife, with few exceptions will be evaluated as a hard use knife. A Spyderco Delica is an EDC or utility knife. So attribute that scores a 2 means that it works well for its intended use. But that exact same attribute in a knife with a different intended use, may score a 0. It is all about how something works for its intended function.

I am going to start out with a classic knife—the Small Sebenza 21 (in the next post). Before I do that though I want to lay out the scoring method. Here is the scoring system:

0: Does not work
1: Works
2: Works well

Here are the categories:

Steel:

Lots of folks know more about steel than I do. In the end however, all of the pros and cons, for me, come down to four things: 1) sharpness; 2) durability (hardness/toughness combined); 3) rust resistance; and 4) maintenance. Knives with more carbon tend to sharp to a finer edge than those with less carbon. Hardness and toughness are two different things. A hard knife is unyielding, cutting and marking other materials but not being cut or marked in return. Toughness is how much the steel will yield without breaking. Diamonds are hard, taffy is tough. Durability is a balance of these two things. Blades that are too hard are brittle and will chip, like a ceramic blade. Blades that are tough but not hard, like 420HC steel, dull quickly. Rust is the bane of steel. It can permanently ruin a knife, so rust resistance is very important. Maintenance is really just how hard the knife is to keep sharp and make sharp again once dull.

VG-10 is a very good entry level steel. It can get sharp, is reasonably durable, resists rust well, and is easy to sharpen. I dislike how fast it gets dull. It is only marginally better than the 420 HC that Buck uses. But it is a good compromise. In an EDC blade, VG-10 gets a 1. It works. But steels like S30V offer many of the same attributes with better edge retention. For me, S30V sits in a sweet spot—good at all four things, so it would get a 2. ZDP-189 is a little better at sharpness and durability, but a little worse at rust resistance and sharpening, but the tradeoffs are definitely worth making. It would get a 2 as well in an EDC knife.

Steel can get outdated. Something that would have been top of the line ten years ago is not now. As such, the score for a knife's steel could change over time.

Grind:

Grind is the three dimensional shape of the blade. For different kinds of grinds see here. For EDC knives a thinner simpler profile works best. For larger, tactical blades more robust and thicker grinds are advisable. In general, complex grinds prevent the knife from slicing well, so there has to be a good reason to abandon the simplest grind possible. I like a full flat grind (FFG), but a good hollow grind or a Scandi grind work well.

Blade Shape:

Blade shape is the two dimensional profile of the blade. For different kinds of blade shapes see here. I like simple blade shapes with a good deal of belly. Belly allow for you to put more movement into a slice, increasing the cutting power of the knife. A recurve works well too, but often times makes sharpening a chore. Whether the knife is plain edge, partially serrated, or fully serrated also depends on intended use. It is hard to justify the partially serrated blade, as many years of use have shown me that it is a “worst of both worlds” kind of option. That said, a partially serrated knife, with enough plain edge blade can work well. The quality of the serrations are important. In particular, I like the CRKT “Veff” angled serrations and the Kershaw “scallop” serrations the best, and the spindly toothed Cold Steel serrations the least.

Lock:

A folding knife is only as good as the lock. The better the lock, the better the knife. For a lock I look for three things: 1) the easy of engagement during deployment; 2) solidity one deployed; and 3) the easy of disengagement. There is no reason to have a two handed disengagement for a lock. Even a well designed lock back and been closed with one hand. I prefer simpler locks as a well executed lock of any design is strong enough for just about any folding knife use. I am not requiring the knife lock to be able to withstand high stress tasks like batonning through wood, but I don’t want it to fail on a run of the mill spine whack test.

Design:

Design is how the blade looks on paper. One big thing I have noticed over the years is that a good blade to handle ratio is the hallmark of a good design. Knives like the Al Mar Ultra Lights and the Spyderco Dragonfly cram a ton of blade for the handle size (the Spyderco Dragonfly has a blade:handle ratio of .72, which is really amazing). Other nice design hallmarks include things like the overall visual appeal and the “orderliness” of the knife. For example, the Spyderco Leafstorm’s lock side is extremely inelegant in design with a crooked clip that could have been used as reinforcement for the lock (functioning like a Hinderer lock stop). Curved or chamfered edges are another nice design touch, as is a choil. Finally small things like the placement of the lanyard hole and the way in which the handle covers up the exposed rear portion of the knife when closed are important design considerations. Weight is an important design consideration as well, with EDC knives falling, hopefully, on the light side; and heavy use knives falling on the heavy side. Again use determines the standard.

Fit and Finish:

If design is how the knife looks on paper, fit and finish is the execution of that design. Clean edges, crisp lines (when they are supposed to be crisp) and a tight fit between parts are all considered. Blade centering is an easy way to check the fit and finish of the knife. Solid lock up with no blade play is another sign of good fit and finish. Also look for clean and even grind lines on the knife.

Retention Method:

How a knife is kept close and handy is really important, especially when dealing with a folding knife. I prefer a clip as it is one less piece to lose or damage. That said, I can see the purpose in having a case or even a clipped case (like offered on William Henry knives). A good clip should hold the knife in place without being impossible to get on and off your person. I don’t really have a preference for tip up or tip down, but being able to choose is nice. I think the standard Strider/ZT clip is probably about the baseline clip—not great but not bad. I do like clips that are more discrete than others, giving an edge to a wire clip like those used on Spyderco knives. Switching handedness of a clip is nice, but if you plan on keeping the knife and not reselling (and that is an important consideration, as knives have a vibrant secondary market), it shouldn’t matter that much as you are unlikely to switch handedness over the course of the lifetime of a knife. If it is for resale than an ambidextrous clip is probably a good idea.

Deployment Method:

There are two main considerations here: assist/auto v. manual and then the actuator (thumb stud, flipper, Emerson opener, thumb hole). I have had many assisted openers and a few autos and a good, well made manual is just as fast. Less parts to break, just as fast, and less weight means that manual, for me, almost always trump an assist/auto. In a tactical application, an assist/auto can serve some purpose. I really like Spyderco’s hole, but a well-designed and well-made thumb stud and flipper are great too. For sheer elegance I like a flipper.

Grip:

I have realized that how a knife feels in hand depends on the inch or so behind the pivot pin. The thinner the better, as it seems to lend the knife a bit of fluidity and control when cutting. The Dragonfly is an excellent study in how a grip should be designed on a smaller knife. For a larger knife where heavy use is possible, the multi-position flexibility of the ZT series represents another, different grip design philosophy. Both work, but it depends on intended use.

Carry:

Some knives seem bulky in the pocket. Others seem to disappear. Some are chores to extract. Others slide out too easily. Often, it is the carry of the knife that dissuades me from making it part of my EDC. This is related to the clip design, but some knives have crappy clips but excellent carry (see the Leafstorm).

An ideal score would be 2 points in each category for 20 points overall. The scale is intended to be logarithmic, so that a score of 20 is MUCH harder to achieve than a score of 10. A 20 knife is more than twice the knife that a 10 knife is.

Next up, the first application of the scoring method: the Small Sebenza 21.

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