Do-it-yourself knife sharpener

It is quite difficult to sharpen a knife by hand. It will take some time to develop the habit of maintaining a constant sharpening angle, which is not at all easy. A tool for sharpening knives can make the task easier. There are factory options. But for good copies you have to fork off a couple of hundred dollars, and this is clearly a lot. The good news is that these devices are easy to make with your own hands. Moreover, many home-made knife sharpeners are no worse in functionality than those from eminent manufacturers, but they are many times cheaper. 

Knife sharpening basics

Knives have different uses, and there are several of them even in non-ordinary kitchens. There is for slicing bread, other soft foods, there is for cutting meat, chopping bones, and other hard objects. And that’s just household items. But there are still those who take hunting and fishing. If you look closely, you will see that they all have a different sharpening angle (this is if they have not been sharpened at home already). It is the sharpening angle that is the most important characteristic, which is determined by the purpose of this blade.

At what angle

The sharpening angle is determined based on the main field of application of a particular blade:

• Dangerous razors are sharpened at 8-12 °. Such a small angle allows you to easily cut hairs after finishing, but if you try to cut something else, the blade will become dull very quickly.
• Fillet knives are sharpened almost the same way – 10-15 °.
• For cutting food, the blade is best sharpened at 15-20°.
  

• For hunting knives and general purpose knives, choose an angle between 20° and 25°. A cutting edge of such sharpness will allow not only to cut soft products, but will easily cope with bones, wood, etc. Some manufacturers of hunting and knives sharpen their blades over a wider range – 20-40 °. A knife with a 40° blade cuts much worse, but it does a better job of opening cans or similar work.
• Heavy knives for special purposes (machetes, for example) are sharpened at 30-50 °. It will be problematic for them to cut bread, but they cut trunks, vines and other similar objects perfectly.

These are general recommendations based on many years of experience. There are, however, options: some blades have several zones with different sharpening. This makes them more versatile, but the complexity of sharpening increases many times over.

It follows from the foregoing that the device for sharpening knives should be able to set the required sharpening angle. And this is the main difficulty in its design and manufacture.

How to sharpen

For sharpening knives, sharpening stones of various grain sizes are used. They are conditionally divided into coarse, medium and small. Why conditionally? Because different countries have their own designation of grit. The most convenient classification is according to the number of grains per unit area. It is expressed in numbers: 300, 600, 1000, etc. Some firms duplicate even English terms. Here is an example division:

• 200-250 – very rough (extra coarse). They are not used for sharpening knives.
• 300-350 – rough (coarse). Used when profiling the cutting edge of a damaged or very dull blade. If the cutting edge has no visible flaws and you do not plan to change the sharpening angle, this abrasive should not be used.
• 400-500 – medium (medium). Many manufacturers do not have bars of this grain size, since it is easy to do without them.
• 600-700 – fine (fine). The main type of whetstones that are used when sharpening knives. They sharpen knives, blunted during normal use.
• 1000-1200 – very fine (ultra or extra fine). They bring the sharpened blade to a mirror shine.
  

In addition to grit, grindstones are also distinguished by origin: they are of natural origin (shale, corundum, etc.), there are ceramic and diamond ones. Which ones are better? It’s hard to say – a matter of taste, but natural ones wear off faster and are rarely fine-grained.

Natural ones are soaked in water before use or simply moistened with it. They absorb water and, during sharpening, an abrasive paste is formed on the surface from water and separated abrasive particles, which increases the efficiency of sharpening. For the same purposes, you can use a special little (honing oil) or a mixture of water and soap (whatever you like). In general, with each of the grindstones, you need to try all these options and choose the best one.

The shape of the grindstone for sharpening knives is a bar, and it is desirable that its length be much longer than the length of the blade – it is easier to sharpen. Convenient bars with double grain – on the one hand larger, on the other – smaller. To sharpen knives for general use, it is enough to have two bars with a medium grain (different) and two small ones (one can be very fine).

Manual sharpening procedure

The device for sharpening knives only facilitates the process of pointing the edge, therefore, knowledge of manual sharpening techniques is necessary. Without them, it is impossible to sharpen the knife correctly.

The procedure for sharpening knives is as follows:

• First we take a bar of medium or large grain size – according to the circumstances, we put it on the table. It is better if it is fixed – there will be no more worries about not moving when working.
• We calculate the required sharpening angle – it is equal to half the selected angle. We hold the blade at approximately this angle. Now the main task is to keep this angle constantly.
• All movements when sharpening a knife without strong pressure. Smooth and even.
• We start sharpening with a movement “from ourselves”. In this case, in one pass, the blade must “pass” along the stone from beginning to end. There is also an important point here: at the point of contact with the bar, the edge should be perpendicular to the direction of movement. There is no problem with the straight part – you drive straight, but as the rounded edge approaches, the handle has to be turned to maintain perpendicularity (see photo).
  

• At the end of the movement, the tip should remain on the surface of the bar. It should not break off, as the point may become dull, and its lateral surface may also be damaged. To make this possible, the length of the bar should be 1,5-2 times longer than the blade. Then the movement will be smooth and uniform, as it should be.
• After the tip of the knife has stopped, we begin the reverse movement.
• We repeat the movements back and forth until a burr forms on the back of the blade – a thin edge wrapped inside. They grope for it with a finger, drawing it perpendicular to the edge (not along – you will cut yourself). Ideally, it should be even along the entire length of the blade. If not, work on more, and not in areas where there are no burrs, but along the entire length.
• When there is a burr, turn the blade to the other side and repeat everything too. The burr will move to the other side, but will become slightly smaller.
  

• Change the bar, and continue to sharpen the blade with movements “away from you” (there is no more reverse movement). Finer grit leaves finer grooves on the edge and slightly less burr.
• On the same grindstone, process the second side.
• Change the abrasive to an even finer one. Repeat everything again (the movement is the same – away from you). And so on until you achieve the “mirror” edge, and it is achieved on a very small bar. This means that the grooves left by the abrasive are very small and the cutting edge is polished enough to cut well.
• But even after that, a burr remained on the back of the blade. We remove it on the smallest bar that you have. We perform the already learned movement “from ourselves” once for each side, gradually reducing the pressure. Thus, it turns out to reduce the burr to a minimum, which almost does not interfere with work.

On this we can assume that the sharpening of the knife is completed. Some still bring the edge on the old belt. A piece of the belt can be fixed on a wooden block (glued, not nailed), rubbed with goyim paste. Then several times alternately hold one or the other side, but turning the cutting edge back. So the last grooves left by the abrasive are polished and the belt is not “cut” at the same time.

How to make a homemade knife sharpener

All homemade knife sharpeners solve the main problem – they allow you to accurately maintain a given angle of inclination of the bar to the blade, which is very important for obtaining a good cutting edge. There are very simple devices, there are a little more complicated, but they allow you to work with great comfort. Choose to your taste.

Simple knife sharpener

In fact, this is a holder for whetstones. Everything is elementary: two triangles of wood, which are connected with studs with “lambs”. A bar is clamped between the corners at the required angle. You can set the angle using a protractor, a special program on your smartphone, or using the rules of trigonometry (right triangle).

When sharpening on such a device, the knife must be kept directed strictly vertically at all times. It’s much easier than holding it at a certain angle.

The same idea has a different embodiment: on a reliable basis, make movable holders into which bars are inserted and fixed in the desired position. Corporate prototype in the photo below.

Homemade tool for sharpening knives made of wooden blocks. It turns out that it is light so that it does not move from its place, it must be fixed with something. In order not to hold by hand, you can use clamps.

Such a device for sharpening knives, of course, facilitates the work, but it is still quite difficult to maintain the angle: you must constantly control the verticality of the blade. Such a habit develops over time, but it is difficult to start.

Fittings on wheels

An interesting variant of a manual knife sharpener with a fixed bar and a trolley on wheels, on which the knife is fixed. It is made on the basis of sharpeners for knives, chisels and planes. With a knife, such a device also works well, but you need to adapt to sharpening the rounded edge.

In this version, as in manual sharpening, the bar is stationary, and the blade of the knife, mounted on a movable cart, moves. The angle is set by the height of the bar relative to the platform on which the blade is attached. The peculiarity of this device is that the table must be level. It can be a countertop made of natural stone, you can put glass on a regular table.

In the embodiment presented above, the angle changes slightly, which is usually sufficient for sharpening the same type of kitchen knives, for example. If necessary, the design can be improved by adding holders (pictured below).

All this is implemented very simply, as it resembles an ordinary constructor: strips, there are holes in them, everything is assembled on bolts and screws.

To ensure the immobility of the bar, there is also a device.

The advantage of this whole design is that it is easy to unfold the knife while maintaining perpendicularity in the rounded area, and it is also very easy to process on the other side: you need to turn the trolley over. For this, four pairs of wheels are made.

Homemade manual knife sharpening machine

Slightly more complex and much more convenient home-made devices, which are made on the basis of well-known branded devices. They have an adjustable platform on which the knife is fixed. The site is set at a given angle. The bar is mounted on a movable bar attached to the rack.

Do-it-yourself devices somewhat repeat the design presented above, but there are some differences. There are many options. Let’s bring some.

Option one: a fixed platform on which the blade is fixed

This fixture is made from the remains of a laminate (you can use chipboard), two steel rods with a diameter of 8 mm and a movable mount.

This design has a fixed base, to which a platform with a knife lock is attached on ordinary hinges. The near edge of the platform can be raised at some angle convenient for work. But other than that, she’s immobile.

On a vertically mounted steel bar, there is a movably mounted latch in which a loop is attached to the side. A rod is inserted into it, on which a bar is fixed. This loop is a simple, but not the best solution: there is no rigid fixation, which means that the corner will “walk”.

Particular attention should be paid to the latch of the bar. Emphasis is placed on the rod at some distance from the edge (about 30-35 cm). This will be the fixed anchor. The second is made movable, it is fixed after installing the bar with a screw and a thread cut into the body of the holder. The second option is to cut a thread on the rod and press the installed bar with a nut.

Knife holder – one or two steel plates fixed on a movable platform. They are fixed movably – with the help of screws and “lambs”. After loosening the fasteners, insert the knife blade, clamp it. It is very difficult to move it. Then, having installed a hairpin with a fixed bar in the loop, its height is adjusted so that the required angle is set.

You can, as in the photo, make templates with the desired angles and achieve the coincidence of the planes. After the transverse bar is fixed, you can work – hold the bar in the right direction.

This tool for sharpening knives works well, but you can only move the abrasive along the blade when sharpening a kitchen knife. Classic sharpening – movement perpendicular to the cutting edge. On the straight part of the blade, this can be achieved. If the blade is short, it will be almost perpendicular, but on the rounded part on the fixed holder, this cannot be done. And all such devices “suffer” from this shortcoming. Once again, they are a great option for sharpening kitchen knives (below is another good option from the same series).

Option two: with a movable platform and a magnetic holder

In this version of a homemade knife sharpener, the problem of previous sharpening is solved. Here the frame remains motionless, which sets the angle of movement of the bar. The bar holder moves freely along the guide, set at the desired angle. The knife is mounted on a movable table. You can, as in the presented version, make a magnetic holder, you can – the usual one from a metal plate and “lambs”. Move the table so that the movement of the abrasive is perpendicular. Actually, everything is in the video. One clarification: in this case it is very important that the surface on which the table with the fixed knife moves is horizontal and even. You can put glass or use a polymer countertop (marble will do too).