KNIFE TESTING (part 1) : GET THE POINT?
KNIFE TESTING (part 1) : GET THE POINT?
Help me design a process to test a blade’s thrusting ability for use in self-defense blades.
Note: My overall goal for this project is to develop testing procedures for knives compatible with self defense needs, while keeping the knife useful for the 99.9% of the time it will be used for day-to-day knife chores.
Ultimately, I would like to have a competition for self-defense knives similar to those for outdoor knives (as seen in the 3rd video below). However, this essay will focus on point design.
KNIFE BOX TEST:
BACKGROUND INFO & REQUEST:
There are many ways to test a blade’s cutting ability. On small knives, you can cut paper, plastic bottles or cardboard tubes.
On larger blades it is common in western cutting competitions to chop through dimensional lumber such as 2 x 4s, cut thick pieces of free hanging rope, or press cut through various tough materials. Among Japanese sword fans, cutting Tatami mats is the traditional choice.
As long as the swords or knives being tested are all cutting the same materials, then you have a good “apples to apples” comparison among the blades being tested.
With the exception of the katana and other blades being tested on the tatami mats (said to simulate the cutting of a similar thickness of human limb), most cutting competitions are done to simulate, not the needs of war, but outdoor tasks, such as those required by the recreational outdoorsman of today.
These tests sometimes lead to overspecialization in blade design to meet the needs of each competition. In western blade competitions, such as those seen at large knife shows, the blades have evolved from big knives that resemble 19th century bowies, to blades that look like long, rectangular meat cleavers with square ends that have no points whatsoever.
We can’t blame the knifemakers for this though. If the rules state that the blades must be no longer that 10 inches in length and the handles must be 5 inches or less, and that the competition will solely be to chop or cut things, then you want a blade whose “sweet spot” or “point of percussion” is as far out on the lever of the blade as possible, and this is going to resemble a meat cleaver, as this is the best design for that task.
In the video below you will see two types of tests: One type is a pass/fail test (as when a competitor cuts through a free-hanging rope in one slice). The other type measures quantifiable differences between blades (as when a competitor cuts through a section of 2x4 lumber in a shorter time than other competitors).
A pass/fail test for the thrust with a large knife could be thrusting into a coconut that is hanging by a cord. If the coconut is split and the water spills out, the competitor has passed.
What I need help designing though is a testing procedure for the thrust that measures quantifiable differences between knife designs: the equivalent for the thrust to the timed chop tests on the 2x4 seen in this video.
In either case, I would like a test that has results immediately visible to spectators, with no need of measurements by judges after the competitor’s run.
BLADESPORTS WORLD CHAMPIONSHIP
Meanwhile, in one of my favorite TV shows, “Forged in Fire” my old student Doug Marcaida has his “Kill Test,” which is specifically designed to test the combat capabilities of edged weapons. In this video Doug uses a Filipino Barong in a sharpness test and a kill test. You can scroll around this video as Doug moves from test to test, following the action between the three stations. (You can pan around the room using the button on the upper left of the screen, or you can hold your curser down and drag right or left to follow the action).
FORGED IN FIRE: 360 SHARPNESS & KILL TEST
While these tests are great fun to watch, I don’t have the budget to purchase ballistic dummies or whole pig carcasses.
Therefore, if we want to create a process to test point design for the thrust on a self-defense blade, how can we do that and make it repeatable with consistent materials, affordable for most martial artists?
In video marked “BOX KNIFE TEST” I showed my first attempt at a testing device. It is a cardboard box, with a 5 pound weight on top to control how far the box slides when you thrust a blade into it. It’s not a perfect test, but it is a place to start. Please give me your suggestions on how to improve this process. The testing device must be simple to construct, affordable and consistent from piece to piece.
Tuhon Bill McGrath
PS: This device is intended to test how various tip designs overcome resistance to penetration.
To text tip strength and handle design, one idea would be to test large knives by thrusting them into a suspended log so that they get stuck and then twisting them out without damage.
I could also use your help in designing a test for tip strength appropriate for thin bladed folding knives.
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UPDATES: Some good suggestions I've received on this topic.
An option for the pass/fail thrust test for large blades could be using a log suspended horizontally. The knife would be thrust into the end grain with enough force to stick into the wood and have to be retracted with enough force to swing the log back towards the user. I think these types of hard impact tests should only be done with large knives with good guards though.
On smaller knives, with no guards and thinner blades (such as many folders), then a softer material should be used for testing. A good suggestion I received was a stack of cardboard sheets covered with a piece of cloth. If we backed these up with a dye filled balloon, then results could be immediately seen by spectators, without the need to have measurements taken by judges.