Anyone interested in three-stage knife sharpening is likely to find a lot of sources on the Internet that offer the simplest solution - a manual or mechanical three-slot pull through sharpener. In the best situation, each of the slots is supposed to perform three different functions: the first slot for deburring, the second slot for sharpening, and the third slot for polishing.
If one continues to look further, however, one will see that it is not as simple as it seems and that there are some other ways and devices which allow you to use this technique for sharpening knives.
The first coarse sharpening or roughing step involves both profiling the cutting edge of the new blade and removing any chips or rolled-over parts. The second stage is aimed at shaping the proper geometry of the cutting edge, and the third stage is aimed at polishing or finishing. All three steps are designed to form the secondary bevel planes that form the cutting edge and must ensure that it is kept sharp.
In a technical sense, the design of the device, which should provide a three-stage sharpening, involves the presence of three different abrasives. That is, the device must contain three abrasives of different grit levels, which, working together, should be able to grind the surface of the secondary bevels after the previous abrasive at the proper level. The better the surface is cleaned, the more stable and sharper the cutting edge can be.
Sharpening your knife is necessary in two basic cases. A less common case in the domestic environment is a knife blade that has not been initially sharpened and has no secondary bevels. This rather specific issue is mostly known to professional sharpeners and experienced sharpening enthusiasts.
The second and most common case is a knife, the blade of which has the original factory secondary bevels or has already been sharpened in one way or another, and the cutting properties of which decreased significantly to the point where the knife has become blunt and does not perform its intended tasks.
To sharpen knives of all sizes and types in the household or in a kitchen one can resort to use of one of the three main ways of sharpening knives, and they are: the use of electric sharpening devices, the use of mechanical devices of various types, and manual sharpening.
The main differences in the approaches lie in the time required to process the blade, as well as in the level of training of the user.
Manual sharpening is one of the most difficult methods in terms of controlling the sharpening angle, but it is also the most accessible and cheapest. However, this method is not relevant to the topic we are addressing.
Many mechanical devices are suitable for such an approach, but the most popular are manual pull-through sharpeners.
Apex type sharpeners are mechanical sharpeners that can significantly speed up this type of process and significantly improve the quality of the sharpening result.
We can distinguish the sharpeners equipped with three slots among the entire mass of electric sharpening devices, which, according to the manufacturers' claims, carry out three-step sharpening of knives.
To use the device, place it on the table and hold it with your right or left hand, depending on whether you are right or left-handed.
Stage #1. The first slot is for honing blunt blades or blades with significant damage such as rolled-over parts or chips. Depending on the specific design, position your knife blade heel in the slot with maximum contact of the cutting edge with the abrasive discs. Try to keep the knife blade level vertical, preferably at all times. For sharpening, you should use translational motions from the heel of the blade to the tip for the whole length of the cutting edge. You should also apply an equal amount of force during the process. Proof of sufficient contact with the abrasive discs will be a characteristic sound. About 10 runs through this slot will be enough for a blade that is not very dull. For blunter or more massive blades, it may take more runs.
For easy repetition of the motion with the same force, in the most upright position and to capture the entire length of the cutting edge, try not to move the blade in both directions - back and forth, but after each pass start the movement from the heel of the blade to the tip. This way you will ensure that you are sharpening the whole blade.
To know that the sharpening stage was sufficient and successful, you should check whether the pre-grinding damage was removed. You can check if the cutting quality is acceptable with a simple test - cut a piece of paper. Hold the sheet of paper upright and try to cut it in one pass. A sharp blade should produce a clean cut without tearing the paper.
After that, you can move on to the next slot.
Stage #2. This slot is responsible for the main sharpening step. In terms of the mechanics of the sharpening process, there is no difference in the actions for this slot. Just follow the above-mentioned instructions.
The only difference may be the number of times you need to run the blade through this slot. As a rule, the abrasive is finer than in the previous slot, and with the same amount of force, you will need the same number of passes or less. Just test the cut on the paper and you will immediately see if the sharpness has improved compared to the previous slot.
Stage #3. The third slot is equipped with a fine abrasive and designed to provide a finer finishing of the secondary bevels, eliminate any flaws left by the previous slot and increase the retention of sharpness of the cutting edge after sharpening.
General Information. Despite the fact that many manufacturers advertise their sharpeners as three-step designs, the sharpening process itself remains two-step, because one of the slots can be for sharpening with 150-grit abrasive, and the other with 200-grit abrasive. That is, there may not be any grinding abrasive in such a design. The third slot in any case is for polishing. Before you purchase, you should ask what each of the slots is in technical terms, as the presence of these slots does not mean that it is a three-step sharpener in the full sense of the word.
An important technical feature of the pull through sharpener is the principle of the V-shaped mounting of the abrasive. All other sharpeners of this kind often do not sharpen, but destroy knife blades by carving grooves in them, which lead to pitting and chipping.
Stage #1. As with the mechanical manual pull through sharpener, the first step of the electric sharpener provides an initial roughing of the blade to remove damage such as chips or rolled-over areas.
The main distinguishing feature of electric sharpeners is that for each side of the blade at each stage there are 2 slots in the form of individual slots for the left and right side of the blade. The blade is placed alternately in the left and right slots and is guided from the heel of the blade to the tip, resting on a guide or a magnet depending on the design. Thus, the blade will run in the slot at a constant angle.
Depending on the level of sharpness or the nature of the damage and the hardness of the steel, you may need to make five to ten runs in pairs. Follow the shape of the blade for proper sharpening or for fixing the entire plane of the secondary bevels, and at the end, to sharpen the tip, you can slightly raise the handle of the knife.
The quality of the coarse sharpening during the first stage is checked by the way the burr forms. To check the burr, simply run a finger across the cutting edge (not along!) and you will feel the burr. If the burr is present along the entire length of the cutting edge, it is a sign that this sharpening stage is complete.
Stage #2. During the sharpening process, the second step repeats the same operations as the first step. Take turns running the knife blade through the left and right slots from the heel to the tip. Depending on the quality of the steel, you may need about 10 runs in pairs to get rid of the burr.
Before proceeding to the polishing stage, the sharpness of the blade can be checked with an ordinary paper test. If the cut is not clean enough, a thin kitchen ceramic whetstone can be used to remove any remaining burr before proceeding to the third stage.
Stage #3. This step includes polishing or finishing of the blade with the fine stone. The actions are the same as in the previous stages. Make several pulls through the left and right slot and then check the sharpness. For a cleaner and smoother cutting you can make a few more pulls in pairs.
General Information. Quality electric sharpeners have the ability to sharpen not only in three steps, but also in a step mode, at different angles. However, such devices are not very common, and they are quite expensive for simple kitchen or household use.
There are mechanical sharpening systems with replaceable abrasives on the market that also provide three-stage sharpening.
The approach here is slightly different. Whereas in the case of a pull-through and electric sharpener, the abrasives are fixed elements of the device, in sharpening systems with replaceable abrasives such as Apex, the consumables have to be individually picked.
Stage #1. During the first stage, depending on the design features of each individual sharpening system, it is necessary to use its manual to clamp the knife blade in the sharpening mechanism, as well as to calibrate and adjust the roughing or coarse sharpening angle. One side of the secondary bevel is profiled by moving the abrasive in both directions - back and forth along the edge of the blade. After the burr is formed, you should switch to sharpening the back side of the blade, until the burr is formed on the other side. Only then you can move on to sharpening with the next abrasive.
To remove the burr, the same abrasive can be used to make a few light pushing strokes along the entire secondary bevel where the burr is. The purity of the cutting edge can be checked with a sheet of paper without removing the knife blade from the clamps. It is enough to hold the sheet of paper with both hands and run it across the entire blade. This will show if you have sharpened the entire length of the cutting edge or not.
Stage #2. During the sharpening process, the second stage repeats the same operations as the first stage, with the only difference that you will need to replace the abrasive with a fine stone. The way to check the quality of the edge and the conditions of the transition to the next abrasive are the same.
Stage #3. The fine abrasive in the finishing stage is used in the same way as in stages 2 and 3. At the end, you should make a few pushing strokes alternately on each side of the blade and that is it.
General Information. The use of some models of mechanical sharpening systems in combination with various interchangeable abrasives may in some cases be somewhat more expensive than using the most advanced pull through sharpener, but it will give you a much higher quality. At the same time, they can be much cheaper than electric sharpeners. There are a number of complete solutions with interchangeable abrasives designed to solve the three-stage sharpening process for different purposes at the highest level.
You should understand that the very concept of sharpening knives in three stages can be achieved with three abrasives, but this is not always effective for some steels and not for all types of knives. It is correct to understand this process as roughing, sharpening and finishing - these are the processes that are intended to form a stable cutting edge and increase the sharpness retention of the blade. That said, there can be more than three abrasives close to each other, for example with 5 abrasives you will get the higher quality of the secondary bevels.
Electric sharpeners provide a high speed of processing and do not require much knowledge or experience from the user. On the contrary, to use a high-quality mechanical household sharpener the user will need to have a high level of specialized knowledge and experience. The maintenance takes considerably longer when using a household knife sharpener.
The difference between sharpening the same knife on a professional electric and a mechanical sharpener can be quite significant, and the result depends on the experience of the person doing the sharpening. Considering that the range of abrasives on mechanical sharpeners is much wider, it makes sense to sharpen expensive knives with this type of sharpeners, because three-stage sharpening is not suitable for expensive knives.
The cost of materials in both cases can be in the average price segment, and often far exceed it.
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