5 Ways To Test The Sharpness Of The Blade
The entire period of the development of metallurgy, from about the second millennium BC, people compared the sharpness of blades in different ways. During this time, many methods of checking the sharpness were invented, some of which have survived to this day.
1. Test cutting
In ancient cultures, the most important cutting tool was not a knife, which belonged to inexpensive household tools, but a sword, which was the main weapon for thousands of years. It was the examination of the sharpness of swords that interested the owners, regardless of culture and geographical location. The methods of such examinations in Europe were eventually lost, but in Japan, the traditions were preserved up to the present. There is a wide variety of ways to test large and small samurai swords, organized into a strict system.
This method is called Tameshigiri (試 し 斬 り, 試 し 切 り, 試 斬, 試 切) - test sword strike. According to tradition, blades are tested by cutting a wide variety of objects: sheaves of straw, bamboo stalks, samurai helmets, various metal plates. In the past, only after such a test, a samurai sword was assigned a price and the master sold it to the customer - testing was the main way to check quality. The cutting technique had special blows: from top to bottom diagonally at an angle of 30-50 degrees; from bottom to top diagonally, while maintaining the angle of attack of 30-50 degrees; horizontal cut with the application of a force vector across the fibers of the material being cut; vertical blow from top to bottom with horizontal placement of the target. In addition, separate parts of the blade were tested: the last third of the sword, the tip, etc.
Nowadays, especially with the creation of the so-called BladeSports in the USA, this practice of testing blades has resumed and has already become directly related to knives. Competitions consist of cutting a variety of materials placed on special stands. Paper sheets rolled into a tube, hanging ropes and sheets of paper, wooden boards, water bottles, and hollow cardboard tubes. Naturally, all these methods of checking the sharpness can be used separately to check specific knives in any conditions, and not only on the stand. However, it must be remembered that knives are created primarily for cutting, and although chopping with a knife gives an idea of the level of sharpness, it also largely depends on additional parameters. In particular, the weight of the blade and its geometry. Not every knife is able to effectively chop solid materials because of the delicate thickness behind the edge and too thin blade.
2. Shaving test
One of the most common and oldest methods of checking the sharpness of the blade is shaving. Most often, the hair is shaved on the forearm. It is believed that the hair should be removed easily, "with a bounce", and the knife should slide withount any resistance. Of course, this method is completely biased, since genetically people have different hair and the purity of such shaving cannot be a reliable test.
3. Paper test
The most common way to check the sharpness of a knife is to cut paper sheets of different densities. The average, so-called "working sharpness" of the knife can be checked on a standard sheet of printing paper with a density of 80 g/m². A higher level of sharpness can be checked by cutting thinner newsprint, the average density of which is 48 g/m². An even more subtle level of sharpness is shown by cutting paper napkins with a density of 18 to 28 g/m². And the highest level is considered to be cutting cigarette paper with a density of 16 to 20 g/m². When cutting, it is not necessary to fix the paper rigidly, it must be in a free state. It is important that the knife should not only cut the paper sheet, but also leave a clean, even cut that shows the "smoothness" of the cutting edge and the absence of chips and jams on it. The test on paper is certainly not an ideal measuring test, but in general it quite accurately shows the state of the cutting edge of the knife.
4. Tomato test (food cutting test)
Test for cutting food products — is the most common household test and at the same time the closest to the actual use of a knife. The sharpness of the blade is perfectly noticeable when cutting products that have a fairly soft, but elastic structure of the pulp and a dense, elastic peel. Traditionally, such materials include tomatoes and fresh bread. Cutting these products with an easy passage of the knife through a dense peel and without jamming the pulp shows a very decent level of sharpness.
5. BESS edge sharpness testers
The development of technology has inevitably led to the creation of electronic devices for measuring the sharpness of blades. One of the most popular and affordable is the American Edge-on-up (EOU) sharpness tester. Its inventor, Mike Brubacher, has developed his own BESS scale ("Brubacher Edge Sharpness Scale") with a specific standard for measuring the sharpness of cutting edges. The device has a special electronic weight sensor that reacts to the pressure applied to the wire stretched between two special stands located on a steel platform. When cutting this wire with a blade, the maximum required pressure for its complete rupture is measured. The lower the pressure required for cutting, the sharper the cutting edge of the knife. The required pressure can be classified accordingly on the BESS scale. The measurement accuracy on this device has an error within 5 grams. Thus, this tester allows you to make a fairly accurate and objective measurement of the degree of sharpness of any knife.