How to hone a knife?

How to hone a knife?

Before you get into the actual process of honing and knife stropping, no matter how strange it may sound, it is absolutely necessary to understand the very essence of the concept and purpose, in order to achieve the best result. 

Any sharp knife, one way or another, loses its sharpness over time and the question arises as to how to make the cutting edge of the knife sharp again.

At this point, it should be noted that depending on the type of blade and the purpose of the knife, you can apply different methods of sharpening, as well as techniques to maintain sharpness, which is commonly referred to as honing, stropping, and some use the concept of finishing. Honing can be rightfully attributed to simpler and more money-saving methods, but there are certain advantages and disadvantages. It is also worth noting that some experts tend to distinguish between the concepts of honing, stropping, and finishing.

We will try to understand the concepts and things directly related to this process on the basis of the following points and develop some kind of training material by asking a number of questions:

1. What is knife honing and what makes it different from finishing and sharpening
2. Materials and tools:
1. A leather strop and a honing rod;
2. A strop for finishing and honing;
3. Stropping compound: pastes, slurries, and emulsions.
3. Tutorial
4. Summary

What is knife honing and what makes it different from finishing and sharpening?

Technically speaking, sharpening, finishing, and honing are the mechanical effects of abrasive material on the surface of the cutting edge of the blade. At the same time, the accuracy of all three processes is very different from each other. So what are the differences?

Everyone who is interested in knives and sharpening understands that during the sharpening process, the impact of the abrasive stone can be quite significant and it produces a burr and a surface of varying levels of roughness on the planes of secondary bevels.

Finishing or the creation of a uniform surface of a high purity level of the secondary bevel planes and the creation of a smooth cutting edge are done in order to increase the wear resistance of the cutting edge. The finished secondary bevels planes should, as far as possible, be free of large sharpening marks, which in turn represent stress concentrations and can lead to pitting. The concept of finishing is also called honing in the industrial field, but such processes are complex and technically complicated.

Therefore, the finishing process can be regarded as a superstructure category and a method of increasing the service life of the knife by improving the secondary bevel planes and the cutting edge without changing the geometry of the knife. In other words, the finishing can also be seen as a finishing process that improves the quality of the surface after the sharpening process itself.

Despite the fact that some methods of finishing are similar to honing, the differences are quite significant and the methodology is not as simple as it seems at first glance. If properly performed, you can keep your knives sharp for quite a long time without having to sharpen them.

Knowing that all knives lose their sharpness and that working with a blunt knife is uncomfortable and not entirely safe, you can resort to honing, as it is a process of quickly bringing or maintaining the sharpness of the cutting edge at the required level with optimal labor costs and acceptable results of the work.

However, you should understand that honing the knife is not a universal solution and that some of the rolled and chipped areas of the edge may not be possible to remove.

It is worth noting that the honing process is suitable for blades with a fine thickness behind the edge, such as kitchen knives, as well as for other knives. The only difference will be in the choice of available and cost-optimal materials.

One of the oldest and best-known materials for knife stropping is leather. In the past, it was most common for barbers to hone a dangerous razor on a special leather strop. If we go deeper into history, razor with a straight blade appeared in ancient Rome at the beginning of our era. 

Leather, glued to a wooden bar is most often used for stropping blades and other cutting tools. Special sharpening compounds can also be used with this technique.

When picking a leather or a paddle strop, the quality and density of the leather and the correct surface of the wood are fundamentally important, as a too-soft leather surface can lead to a change of the angle of the cutting edge and a non-aggressive cut.

You can buy a leather strop with already applied sharpening compound of a certain grit or without it. The advantage of the clean strop is that it can be used more flexibly and universally in stropping. This includes applying the paste yourself if necessary. If you are not sure if you can do it correctly, you can buy a strop with a layer of compound already applied. The strop can have one operational side or two. One side usually has a coarser paste and the other side has a finer paste, which provides a finer stropping.

Unpleasant results can occur even when working with a good quality leather strop if the correct angle is not maintained, especially when the paste is applied to the leather.

The reason is quite simple and has been proven experimentally with the use of a guided sharpening system. When performing a pulling motion during stropping with a leather strop and gradually increasing the angle by up to 1 degree, a definite decrease in cut quality was found after pre-sharpening on 440c steel with a hardness not higher than 58-59 HRC. If you don't have enough skill, the probability of ruining cutting-edge increases.

In addition, there may be scratches on the edge between the secondary bevels and bevels planes, or the transition between the clear boundaries of the planes may be somewhat over-polished, which is also inappropriate. Thus, each side of the edge may look a little different and may simply lose its neatness and aesthetics. These kinds of mechanical errors are unpleasant, but are not significant and will not affect the overall performance of the blade and can be corrected later.

The mechanics of stropping with leather are quite simple:

1. Try to keep the same angle. You should know the angle from the process of sharpening each individual knife;
2. Remember to work with pulling motions, as you can easily damage the leather surface;
3. Make 20-30 stropping movements on each side of the edge;
4. You can alternately make movements from the tip of the edge to the ricasso (tang of the blade) and back again;
5. If you use a sharpening tool with a guide, set the same angle or a little more. Everything else remains unchanged;
6. Use an abrasive compound when required.

Honing rods

Another fairly common tool, used mainly in the kitchen, is a honing rod. The basic rule for honing rods is the length that approximately coincides with the length of the knife blade. There are also honing rods with an oval cross-section and which have a large radius. This point provides a large contact spot and makes the honing more convenient and of higher quality. 

There are three groups of honing steels of different lengths and roughness:

• Ceramic
• Steel
• Diamond

Ceramic honing rods often have a very smooth and even surface. Such rods are suitable for dressing knives of any hardness. Roughness levels vary from manufacturer to manufacturer, so it's worth asking about it before purchase.

Steel honing rods are usually made of tool steel of high hardness about 65 HRC with the addition of chromium for increased wear resistance. Some manufacturers have two grit sizes: medium and fine. A medium grit rod is mainly used for kitchen and utility knives. A rod with a fine-grained surface is mainly used for butcher knives pre-sharpened on a grinder or grindstone. 

Diamond honing rods, unlike the previous two, have higher abrasive power and serve as a quick sharpening tool, so it is necessary to handle such tools with care and understanding.

In some cases, the price of a honing rod may be an indicator of its quality.

The technique of using the honing steel comes down to the following points:

• Regardless of how you are holding the knife and the honing rod, the surface of the rod should coincide as much as possible with the angle of the secondary bevel of the edge, and the movements are made from the tang of the blade to its tip
• Sometimes it is recommended to simply rest the honing steel on the table at a certain angle you want, then you can move the knife blade vertically from the tang to the tip
• The process continues until you are satisfied with the result

In some rare cases, full-size hard natural or synthetic stones have a rounded chamfer on one of their corners, in which case the stone can also serve as a honing rod.

In addition, the main surface of any hard, full-size stone, regardless of whether it is of natural or ceramic-bonded origin, can be used for honing. 

However, this use is designed more for sharpening professionals and is associated with a completely different range of the price of tools.    

A strop for finishing and honing

In addition to the aforementioned methods, materials, strops and sharpening tools, there is also a technique of using sharpening stones in combination with guided sharpening systems. 

Among all the abrasives, first of all, it is worth distinguishing one particular category of abrasives, which are mainly used as lapping stones. The abrasives can be leather-based, metal, wood, ceramic, and natural stones.

Depending on the level of surface roughness of one or the other abrasive, not depending on the material, there is a possibility to work with different results on different steels in order to hone the secondary bevels and/or cutting edge depending on the level of damage.

In other words, it is not always necessary to resharpen a blunt knife, but it is enough to just slightly hone the cutting edge. Therefore, it is possible to use such materials if they are available. It is not reasonable to purchase them especially for this purpose.

One of the advantages of such abrasives is their compact size and low weight, which makes it possible to use them not only in the household, but also in nature. This is very similar to the way mowers always used to, and still do, carry a small bar to strop a hand-held scythe.

The honing process is not much different from stropping with leather strops, with the only difference being that you can work with pulling motions as well as with pushing motions, by hand or with a sharpener.

Metal lapping abrasive

Since we talked about leather strops  above, let's move directly to metal bars based on cast iron. If your knife only needs to have its cutting edge honed, this is similar to the deburring process and such a bar may well be used for this purpose.

Wooden lapping abrasive

Wooden abrasives come in a variety of hardnesses, but they can also be covered with painter's tape and applied with an abrasive compound. In this case, you should work only with pulling motions. This way, however, only very minor damage can be repaired. 

Ceramic abrasives

These stones have a high level of hardness, so it is worth, as in the case of the ceramic honing rods, to choose not too smooth ones if you decide to hone the cutting edge, but you need to be careful not to change the geometry of the secondary bevels.

Natural stone abrasives

There are not many natural stones hard enough to be used for finishing of the cutting edge and they are often quite expensive. The results for chamfering or so-called micro finishing are often the best. Therefore, if the edge of the blade is not significantly damaged, it is possible, with experience, to hone the cutting edge in this way. 

One rule for all types of compact-sized stones is that they give the best results when used in combination with guided sharpening systems.

When describing leather strops, we were talking about using different pastes. The leading manufacturers most often have several different grit sizes that you can use at your discretion when applying to different lapping bars.

As a sharpening compound, pastes can be different in their composition: CBN, with diamonds, and on the basis of aluminum oxide.

CBN and diamond pastes in their pure form are used with steel or cast-iron bars but are most often used in combination with oil-based coolants.

In its pure form, an aluminum oxide compound can be applied directly to the leather on strops, as well as on a masking tape glued to a wooden bar. If you dilute the paste with an oil-based coolant, it can be applied to natural and fairly smooth ceramic bars, as well as cast iron and steel bars.

Slurries and emulsions

There is a range of slurries and emulsions available for purchase that are used for polishing, but they can also be used for honing in some cases. On the basis of the coolant and paste, you can make your own slurry of different concentrations, which will be similar in its principle to the use of a natural slurry with water. It should be noted that the use of such an approach is designed for professionals and requires rather considerable skill and is rarely used if we are talking about honing and not polishing.

In order to learn how to maintain the correct angle and to be sure that you reach the cutting edge, it is enough to put several dots on the secondary bevels of the edge with a black marker and slowly make several honing motions on the rod at the required angle with each side of the edge of the blade. Then check the state of the marks and you will understand whether you are honing at the required angle or not. Over time, you will develop motor skills, and you will be able to hone each side at the required angle without the marker. Afterward, you can simply wash off the marks with alcohol, rinse with water, and you can use your sharp knife without the complicated process of sharpening.

Tutorial

Of all the training materials that exist, the most accessible are the videos on the Internet. The videos are quite extensive and from them you can compare the techniques and methods used by different specialists. There is no doubt that there may be a specialized knife store in your area, where you can also find out the details you are interested in. Some companies also offer knife sharpening courses, which you can simply sign up for hands-on training.

Summary

Each of the described methods of honing or stropping, whether with leather strops, with a honing rod or with different stones, has its own advantages and disadvantages. Working with leather strops and honing steel is easy to learn, but may be somewhat inaccurate, yet it is a relatively inexpensive method. Honing with the use of stones, and even more so with a sharpening system, is more difficult to learn, but the level of accuracy is quite high. At the same time, the cost of this method is much higher.

Thus, it is worth choosing a method and tools for honing and stropping knives according to the criteria of maximum technical feasibility and justified financial costs. Besides, do not forget that the time spent on studying a tutorial will surely pay off.