Evolution of devices for manual sharpening

High-quality sharpening has always been the main condition for working with any tool. Since the beginning of the use of metal tools by humans, the question has always been: how to sharpen them to the maximum sharpness? To do this, we experimentally identified abrasive materials that can quickly remove metal, various loose and solid natural substances, and stones of special types that are most suitable for such grinding tasks.

It is obvious that for many centuries the process of manual sharpening itself has not changed. The master sharpener took a specially leveled stone, pressed the sharpened tool (knife, chisel, scissors, etc.) on top of it, and used a lubricating liquid: water or oil to sharpen it. If the object to be sharpened was of a large size or complex geometry (sword, scythe, etc.), it was fixed as firmly as possible and small stones were used to grind the cutting edge. The main problem with this work was the constant keeping of the angle. Moreover, this problem was typical both for manual sharpening and for sharpening with the help of special grinding machines. The constant angle was maintained manually on both the grindstone and the rotating wheel. Only a sharpener of the highest class could perform such work qualitatively, and of course, there were very few such specialists. However, all iron products were then made of soft carbon steel, which was used until the early 20s of the XX century. They took sharpening quite easily and blunted quickly, the very concept of sharpness was extremely relative. However, the increase in hardness and the transition to high-quality stainless steels significantly changed the situation. A different level of sharpening quality was required, and on an industrial scale, it was achieved through the use of electric sharpening devices. However, devices for sharpening knives and tools by hand are not a thing of the past. They have become an attribute of home sharpening and the most accurate professional sharpening used for the hardest premium steels and expensive artistically designed knives. At the same time, the methods of holding the angle changed over time.

The simplest way to hold the angle when sharpening was to create a special guide (in slang called "crutch"). It is a metal rod with clamps put on it, in which the knife is fixed. Due to the movement of the clamps along the rod, the sharpening angle was set, to sharpen the other side of the secondary bevel, it is also necessary to turn the entire structure with a clamped knife. The main disadvantage of this device is the inability to accurately set the angle on this device, since it is difficult to use an electronic protractor with such a design, it will allow you to set the angle only with a large error. It is also necessary to understand that the force applied by the sharpener to the guide can not be the same throughout the work. Moreover, the force should be evenly distributed over the entire length of the knife, and if the knife has a long blade, it will have to be sharpened in parts, since the length of the stone surface is not enough. And in general, to work with such a device, you need to have a high sensitivity of the hands and it is especially important to have it when finishing and polishing the blade. Because with each subsequent thinner stone, it is necessary to reduce the pressure and by the time of polishing it should be minimal. In addition, step sharpening or creating a micro-bevel remained an exceptionally difficult task. Sharpening a convex lens with such a guide was not possible.

Subsequently, the design of the guide was slightly changed and acquired additional elements in the form of special rollers. They no longer allowed you to drive the guide with your hands, but to roll it on the stone. Such a device became known as a carriage and was used primarily for sharpening carpentry tools: plane knives and chisels. There was also the problem of not being able to sharpen long objects. And when sharpening short metal surfaces, uneven wear of the stone occurred. And if this method of working on inexpensive abrasives was possible for the tool, the carriage was not suitable for knives. It was necessary to look for another solution. And over time, it was found.

This solution was the creation of an abrasive holder on a long metal rod. When using it, it was no longer a person who drove the knife on the stone, but the stone moved from above on the surface of the knife secondary bevel. Initially, such a sharpener was held with one hand, and with the other, the sharpening was performed. The size of the knife available for sharpening immediately increased, and it became possible to sharpen long blades. However, this format required a lot of physical effort in the case of sharpening hard steel and long work. The variety of angles in such a sharpener was limited by the small number of holes in which the guide was fixed. A step sharpening and the creation of a micro-bevel became impossible because of that fact. Creating a convex edge was theoretically possible, but inconvenient due to the technical characteristics of the sharpener. 

In order to make the work of the sharpener more convenient, a sharpening system was developed, which included a platform for placing the knife and a special lift that allows you to adjust the angle setting. This solution made it possible to increase the accuracy of the angle adjustment and fully use the digital protractor when sharpening. Now the sharpener could work with step sharpening and easily make a micro-bevel. In addition, the control over the pressure on the abrasive has significantly increased. There is an opportunity for comfortable and easy polishing of the blade with the help of special polishing pastes and natural stones. But at the same time, to turn the knife over and cut through the other side of the secondary bevel, it still had to be lifted from the platform or removed from the clamp. Thus, after the flip, the position of the knife changed, which affected the accuracy of catching the angle. The solution to the problem was the creation of a rotary mechanism.

The rotary mechanism of the TSPROF sharpeners is a complex mechanical system that allows you to securely fix the knife, set the angle for sharpening with a maximum permissible error of 0.2 degrees and observe symmetry when sharpening both sides of the cutting edge of the knife. The rotary mechanism can be fixed by a tension wheel or a special lever, which gives the sharpener rigidity, preventing the appearance of backlash. At the same time, the knife can be easily and quickly turned over, maintaining the angle.

For the accuracy of setting the angle, a special lift is responsible, made in the form of a rack-and-pinion lift (on a TSPROF K03 sharpener), and the V. C. lift system. Angleset (on a Blitz sharpener) or arc stand (on a TSPROF Kadet sharpener). Thus, the rotary mechanism, combined with the rack-and-pinion lift, allowed to solve many problems of sharpening that were in the past. The angle of sharpening remains the same when turning, it is possible to create a convex, as well as a micro-bevel and step sharpening. Modern sharpeners make sharpening a pleasant and comfortable enough occupation, and turn routine work into an exciting hobby.