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Sharpening a kitchen knife on a homemade machine

A comrade asked to sharpen a knife that was used in the kitchen for 3 years for a variety of tasks: cutting frozen meat and poultry bones. The blade of steel 95X18 did not withstand the tests, and several chips appeared on the cutting edge, and the first 50 mm from the tip were initially “undersized”. The owner was afraid to do any manipulations himself, although his kitchen has an abrasive bar from a hardware store.
Sharpening a kitchen knife on a homemade machine
Sharpening a kitchen knife on a homemade machine

Advantages and disadvantages of "purchased" sharpening machines

The most common reason for failure when sharpening a knife is the difficulty to keep it in position so that the approach angle remains constant. There are a lot of tools and machines that solve this problem. The main advantage of sharpening systems made in production conditions is readiness for work,However, they have some drawbacks:
  • Most of the devices can only work on fixed angles (kitchen electrical sharpeners, Lansky type appliances).
  • Systems with good functionality, such as Apex Edge Pro (Price about $ 300), cost a lot of money. Moreover, there are more clones and fakes on sale than originals.
  • Almost all mechanical sharpeners remove a huge amount of metal and overheat the cutting edge. Exceptions, such as Tormek (Tormek T9 costs more than 50 thousand rubles in the minimum configuration. Equipment for the machine will have to be bought separately and also expensive.), Are ADSKI expensive.
  • Not all "factory" designs fix blade tough enough.

Self-made sharpener

At least a thousand knives, chisels and other cutting tools have been on the self-made fixture that I use, so I do not doubt its effectiveness . The construction is extremely simple, and the most expensive in it are grinding stones. In the description I will not give specific sizes, only general ideas.
Sharpening a kitchen knife on a homemade machine

The bed

The bed is a piece of hardware from the Young Binder kit.It is quite large and massive, so it does not falter even on “curved” grounds.
Sharpening a kitchen knife on a homemade machine

Stand

The tripod from a photo enlarger turned out to be an excellent donor. The standard lifting mechanism, which in my case serves to adjust the angle of the stone relative to the blade plane, smoothly works and is securely fixed.
Sharpening a kitchen knife on a homemade machine

Inclined bar

A 10 mm diameter calibrated bar is designed to hold and move a grinding stone. It is attached to the mechanism of lifting through the hinge - the steering tip from the kart. The following parts are put on the bar: plastic nut, spring, two clips with fixing screws, nut at the back (so that the rod does not fall out of the hinge). This design allows you to work with stones of different lengths and change them quickly: I never fix the locking screw of the proximal clamp, and the clamp is held by the force of the spring. The mechanism of fixing the blade Elements of the mechanism:
  • Bracket. The part is made of duralumin and serves as a clamp.
  • The bronze bushing with a semicircular groove is clamped motionless in the bracket.
  • The shaft is set with a gap of 0.1 - 0.15 mm, that is, it rotates freely.The spring presses the locking axis to the hub.
  • The channel is fixed to the shaft fixedly.
  • Two pairs of sponges with M8 hammer bolts move freely along the grooves in the channel bar. After tightening the nuts, they are firmly fixed in position. The angle between the surfaces of the jaws adjacent to the shelves of the channel is about 75 degrees.
The bushing is made on the lathe, the sponge and the channel - on the milling, the bracket - on the boring. The remaining parts and blanks in the garage.
Sharpening a kitchen knife on a homemade machine
Sharpening a kitchen knife on a homemade machine
Sharpening a kitchen knife on a homemade machine

Sharpening

If a used knife is sharpened and you need to keep the approach angle, then the work is done in the following order . We clamp the blade in the jaws, having previously adjusted their position in width. Knives with a polished blade before installation are sealed with masking tape so as not to leave scratches. Sketch the cutting edge with a waterproof marker.Install the abrasive bar with the largest grain. We make a few neat barbell movements from yourself. On abrasion of traces of a marker, we determine whether the angle is selected correctly. If the stone clings along the edge, then it must be increased, i.e., the hinge should be raised. After correcting the angle, the abrasive should remove traces of the marker along the entire plane of the cutting edge. Now you can proceed directly to sharpening. We perform reciprocating movements with a barbell and move along the edge of the knife until chipped, collapsed and other defects are gone completely. We make light pressure only when driving away from you. Return the bar should be idle. At the last passages we ease the pressure on the bar.
Sharpening a kitchen knife on a homemade machine
Pull the channel towards us and turn it 180 °. We work until the width of the supply on both sides is approximately the same. For visual inspection of the edge does not need to constantly bend down. One of the advantages of the device used is that the knife is attached once, it can be turned as much as you like, and it will always stop at the desired positions. When finished with the second side, a burr will appear on the first.It can not be seen, but it is clearly palpable fingers. You need to make sure that the burr has formed over the entire length, otherwise, then "stupid" areas will remain and the work will have to be redone. You need to control the burr with the movements of your finger from the butt towards the cutting edge, but not along it! Otherwise, cuts can not be avoided.
Sharpening a kitchen knife on a homemade machine
The width of the cutting edge along the blade depends on the geometry of the slopes. On this knife, the tip at the tip is thicker than the rest. Before passing to a smaller abrasive with a sponge or paper towel, remove the sawdust. Remove the risks of the previous stone on both sides. In this case, the burr should be separated: do not crumble in the form of dust, but fall off as thin threads. Depending on the grain size of the second stone, you can also "kick" the burr. In my case, that was the case. Then we go to the next grain. We check the result of the work on the newspaper: we make a cut with a broach and control its smoothness. If there are defects, they will cling.
Sharpening a kitchen knife on a homemade machine
If you wish, you can try to shave your hair at the wrist.
Sharpening a kitchen knife on a homemade machine
The best way to check is to cut with a knife what it is intended for.
Sharpening a kitchen knife on a homemade machine

Abrasive stones

I use a set of diamond bars on a metal bond (4 pieces). Coolant - tap water. Some sharpeners wet diamonds with a soap emulsion. Someone generally works "on dry" (see video). I do this in accordance with the instructions of the stone manufacturer, who recommends wetting the bar with water and periodically rinsing metal filings with a brush. The grain sizes on the bars (in microns):
  • 125/100 - forming a cutting edge, changing the angle of sharpening;
  • 63/50 - rough grinding;
  • 20/14 - fine grinding;
  • 7/5 - polished.
I started working as the first stone, and finished the third. I use the fourth rarely enough, only at the request of aesthetes. Instead of diamond bars, it is possible to work with artificial stones from electrocorundum. There is an even more budget option: stick a strip of emery paper of different grit on the forms of aluminum or glass.The most important thing is that all the stones in the kit must be the same thickness.

Video for sharpening the knife

In the video, the huntsman sharpens his working knife (steel Bohler M390) on the device described above. He uses only one 63/50 stone and thinks that's enough. Characteristic movements along the edge - so he removes the burr. Perhaps I missed something in the description of the process or device, deviated from some canons, I do not pray for Arkansas and Japanese water stones. I suggest discussing these points in the comments.
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