Before we start talking about the sharpening direction of any cutting tool, whether it’s a knife or a woodworking tool, it is extremely important to first understand: why this question arises at all, and how knife sharpening actually takes place.
From a mechanical point of view, sharpening a knife blade is a set of actions aimed at creating a sharp cutting edge at a certain angle. During the knife sharpening process, various abrasive stationary and moving materials are used, which can be operated manually or with electric equipment.
In the classical sense, sharpening a knife by hand or using mechanical devices is achieved through abrasive stones of various sizes and types. When manually sharpening a knife, it involves systematic reciprocating movements of the knife blade relative to a stationary abrasive at a certain angle.
Specialized sharpening devices use the same principle, but here the abrasive moves relative to a fixed blade.
Automated sharpening of knives on electric devices involves various sharpeners with rotating abrasive wheels or disks, as well as various belt-grinding machines with endless belts. This type of sharpening involves abrasive elements constantly rotating while the knife blade remains fixed or moves relative to the abrasive according to specified parameters.
During the knife blade sharpening process, abrasive materials remove a layer of steel from the blade at a selected angle to shape, correct, sharpen, and finish the bevels, thus creating a sharp cutting edge.
An inevitable result of processing the bevel surfaces is the formation of a burr, and a certain kind of deformation of the cutting edge occurs. It is at this stage that two concepts arise: sharpening edge leading ("push") and sharpening edge trailing ("pull").
In other words, if we take the example of classic knife sharpening on a full-size abrasive stone (whetstone), the motion of the blade with its cutting edge forward from one side of the abrasive to the other is sharpening "edge leading" ("push"). This motion resembles whittling a stick.
PHOTO 1. Sharpening direction “Push” (“edge leading”)
In another case, when you place the knife blade bevel against the abrasive and move the spine forward towards the opposite edge, this is sharpening "edge trailing" ("pull"). It’s similar to the motion used for stropping a razor on a leather strap.
PHOTO 2. Sharpening direction “Pull” (“edge trailing”)
Looking slightly ahead, it must be noted as an undeniable fact that sharpening "edge leading" forms a much smaller burr compared to sharpening "edge trailing." It is precisely this fact that generates various interpretations and endless debates about which direction is the right way to sharpen a knife.
For a more precise understanding of the topic, we will examine aluminum foil and rather coarse sandpaper.
PHOTO 3. Bevels, cutting edge, burr
In the microscopic world, steel behaves just like real plasticine, and abrasive particles often create quite deep scratches.
Experiment: Fold foil tightly several times, then try to move it across sandpaper, "edge leading" and "edge trailing." You won’t wait long for the results, and they will be different.
If you move the foil "edge trailing," abrasive particles will scratch it, and you will end up with ragged edges and fringes hanging in pieces from the folded edge of the foil. In the microscopic world, this fringe at the forming cutting edge represents the burr.
If you take the same tightly folded piece of foil and move it several times "edge leading," the edge will certainly still tear, but the resulting fringe will be smaller.
In practice, many might say that when sharpening "edge leading," it's impossible to see or feel the burr with your hands. This is both true and false, as much depends on various circumstances. The fact remains that a burr, even a very minor one, still exists, even if it is difficult to notice or detect.
The main difference between the two directions or methods of sharpening a knife lies in how exactly and how large the burr forms.
Another point: working with only one of the presented methods is a very time-consuming process when manually sharpening a knife. This is less relevant for automated processes or sharpening on electric devices.
In the sharpening process using "push" ("edge leading"), a smaller, denser, and more uniform burr forms. Because of this, the cutting edge becomes more homogeneous.
When sharpening "pull" ("edge trailing"), the opposite happens — the burr stretches more, and the cutting edge will be less uniform, more ragged, and inconsistent.
In both cases, during sharpening, deformation of the cutting edge occurs. Several factors play a role here: the chosen sharpening angle and the blade steel structure near the bevel. The strength, toughness, and uniformity of steel are also integral determining factors of this process. It can be confidently stated that every blade is individual, and each sharpening will produce different results.
Based on these reasons, we have enough information to consider.
Despite such technological differences, for effectiveness, it is advisable to combine both approaches. This is especially true for sharpening knives on TSPROF sharpening devices, since maximum effectiveness on these devices can be achieved by employing reciprocating movements "push" ("edge leading") and "pull" ("edge trailing") using a moving abrasive and fixed knife blade. This process is facilitated by the guide rod with the abrasive holder set at a specific angle, ensuring repeatable results.
PHOTO 4. TSPROF Sharpening System
Under these conditions, we obtain a result somewhere between the two methodologies in terms of quality. In defense of this method, one could argue that compared to exclusively sharpening "push," no practical evidence has proven that a cutting edge sharpened by the combined method or reciprocating movements of the abrasive is less durable.
Separately, a factor such as the level of steel heat treatment and the use of various types of abrasives should be highlighted. However, this is a different topic, causing many discussions, and could be expanded into a separate narrative.
It’s perhaps worth mentioning only briefly that abrasives of identical or approximately similar grit can produce vastly different results on the same steel, determined by the type of abrasive particles and the abrasive binder itself.
When sharpening a knife on a full-sized coarse stone or a whetstone, it is recommended to sharpen "pull" ("edge trailing"), whereas on medium and fine-grained whetstones, it's the opposite — sharpen "push" ("edge leading").
It's also desirable to maintain the transition between coarse and fine abrasives when manually sharpening knives. When switching to a finer stone, you can make a gentle motion, "edge leading."
If you need to repair a severely damaged knife blade or re-sharpen the knife to a new angle, it's quite possible to use reciprocating movements.
When sharpening a knife blade on household desktop sharpeners, it is recommended to sharpen using the combined method, as this is the most productive solution. Use "push" ("edge leading") movements in the finishing stages, employing dense and fine-structured abrasives. Movements "pull" ("edge trailing") are recommended on very or ultra-thin edges, very fine and soft abrasives, and also when using leather strops.
On certain automated electric sharpening devices, you can choose the part of the rotating sharpening wheel where sharpening "edge leading" or "edge trailing" can be performed depending on what exactly needs to be achieved on the sharpened tool. In other words, everything depends on the intended use of the blade, steel quality, and the specific knife.
However, it should be noted that in such a case, not every abrasive can be used in both directions. This circumstance is due to faster abrasive rotation, and there is a potential risk, in case of error or incorrect blade removal, of damaging the surface of the abrasive disc.
In the case of manually driven devices, this generally cannot happen. There are only two possibilities — using a leather strop or a very, very soft, ultra-fine finishing abrasive stone or a whetstone.
You can sharpen in both directions on coarse abrasives, but on fine-grained abrasives for finishing the bevels, it's best to perform movements "edge leading."
When sharpening a knife on devices like the APEX sharpening system, the burr can be removed during the edge finishing process. In other words, when you switch to the final fine finishing abrasive stone and finish processing the blade, you need to perform movements "edge leading," running the blade from the heel to the tip, flipping the blade to the other side after each stroke, one stroke per side of the blade, totaling around twenty strokes.
The longer and more carefully you perform the finishing, the higher the quality of the bevel surface you can achieve, and the less likely you are to damage the fine abrasive with the burr.
Some sharpening experts recommend movements not only "edge leading," but also slightly diagonally along the edge. This movement aims to cut off the formed burr. However, not all stones can handle this neatly. The TSPROF Alpha resin bonded diamond stones, due to their structure, handle this quite well.
Thus, one critical aspect influencing the sharpening result is the proper removal of the burr. Technically, this process is known as performing a "technological barrier."
The technological barrier is best executed on a flat and hard surface. Ideally, a surface plate or the surface of a steel or cast-iron strop is suitable for this. For this, fine-grit sandpaper can be used. Burr removal movements ideally are made across the formed cutting edge. Thus, you are polishing off the burr rather than breaking it off in a barbaric manner.
For knives, of course, applying this method in its pure form is difficult. However, another solution exists aside from the one mentioned above.
To strengthen the cutting edge and reliably remove the burr, you can create a micro-bevel on the blade. These are additional bevels on the blade edge with a slightly larger angle, differing from the main angle by about 1-2 degrees.
You can apply this technique for knives with thin bevels sharpened at fairly acute angles.
PHOTO 5. Example of a micro-bevel
Creating an explicit micro-bevel isn't always necessary — you can use the finest abrasive at the finishing stage and, with gentle movements, "edge leading," remove any possibly remaining microscopic imperfections.
Everything mentioned above can also be transferred to sharpening a knife blade on a stationary abrasive. The mechanics will simply be exactly reversed. To remove the burr, the blade needs to be drawn across and forward along the abrasive, performing a curved motion. The crossing movements facilitate burr removal.
If you're a beginner and haven't yet decided, we recommend experimenting. Try sharpening, and accumulated experience will guide you in choosing how and on what abrasive to sharpen knives made from different steels.
All TSPROF sharpeners feature a rotary mechanism and fixed angle, allowing you to concentrate on abrasive movements without needing to maintain the sharpening angle, especially when flipping the knife.
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