Knives are indispensable items in the household. In the kitchen where food is cooked, sharp knives are needed. Hunting and fishing are inconceivable without this tool.
The working part dulls over time and loses its sharpness. Of course, you can sharpen in the nearest workshop. But if the household uses dozens of knives of various shapes, then a frequent trip to the grinder can be expensive.
In the distribution network, you can purchase many tools for sharpening cutting tools. As a rule, the effect of their use depends on the quality, company of the manufacturer and the skill of the owner. Making a knife perfectly sharp with such sharpeners is almost impossible.
What is the design
Manual grinding machine is a simple device. The scheme by which it operates is that the knife is rigidly fixed, and the grinder moves along its blade.
The equipment is equipped with an adjustment that can change the angle of inclination of the abrasive in relation to the blade. A professional tool is sharpened at an angle of 20 °. Kitchen knives are processed at an angle of 30 °.
Self assembly: work steps and material selection
- The basis for the machine is a wooden board 15–20 mm thick. This size is explained by the fact that the support must have sufficient weight. The platform is made of a piece of laminated chipboard or MDF. The shape of the base resembles the head of a key to a conventional door lock, but can be rectangular. The material of which the platform is made does not really matter. This is a duralumin or steel plate.
- A steel vertical rack is installed in the wide part of the board. The rod is made of steel round profile Ø8-10 mm. A thread is made along the entire axis.
- To mount the rack in the board, a hole is drilled with a diameter equal to the transverse dimension of the axis.
- At the bottom of the platform, a circular recess of Ø20 mm is made. Its depth should hide the nut flush with the bottom surface of the wooden base of the machine.
- The rack is fixed on the plate with two nuts - above and below. Washers are placed under them.
- There are other options for installing the supporting rod. For this, special bushings are used. The main thing is that the mount is reliable and provides a strict vertical axis.
- A rack with a horizontal slot is put on the rack. The part is a segment of a bent metal profile of a T-section. Some craftsmen make it from a steel strip.
- The bar has elongated shelves (ears) on the side. They install nuts.
- Then the plate is screwed onto the axis. By rotating the element, the desired height of its position is achieved. Setting this parameter details provides the desired angle of inclination of the abrasive bar in relation to the blade of the knife.
The design of the strap may be different. It all depends on the imagination and capabilities of the master.
- On the near side of the platform, two clamping bars are installed. Elements are made of two metal strips fixed with screws or bolts on the board. The clamps provide a rigid fixation of the blade of the sharpened knife perpendicular to the axis of the machine.
- The abrasive element is clamped in a special case with a long metal rod.
- The rod is threaded into the hole of the bar.
- Using a factory-made abrasive bar is extremely disadvantageous. A trail of wear quickly appears on the working side of the bar. To get rid of it, you have to grind or make a replacement.
- The abrasive is moved across the blade, pressing lightly against the knife. This movement of the whetstone allows you to get a chamfer even in width.
- The platform is fixed with a clamp on the worktop of the workbench.
Abrasive Bar Production Example
You can make a grinding device like this:
- From thick Plexiglas, preforms are cut with a size of 20 × 40 mm across and a length of 200 mm.
- On each fasten a strip of sandpaper. Usually use PVA glue.
- Plexiglass has good adhesion, and sandpaper adheres tightly to its surface.
- On the side of the bar with a felt-tip pen write the number of emery grit.
- A hole with a depth of 120 mm is drilled at the end of the Plexiglas. Its size should provide a tight fit of the guide rod. The part is a metal rod with a diameter of about 4 mm.
Knife sharpening consists of several stages of blade processing. In the process, the bars change. Go from coarse-grained abrasive to finer sandpaper. The final grinding of the chamfer is done by nulling.
Sharpening curved chamfers
The endings of the blades of professional hunting knives are curved. To sharpen the curved surface of the blade, the tool is fixed so that the chamfer of the end of the blade falls into the working area of the abrasive element. A bar rod threaded into the hole of the bar has freedom of movement in the transverse and longitudinal direction, which allows you to process bevel curves without compromising quality.
Abrasive change
Experts say that one strip of sandpaper is enough to process two knives. It is enough to hold a bar with worn paper under a stream of water for a couple of minutes - and the sandpaper will easily go away by itself. It remains on the dry surface of the bar to stick a new strip.
It is not necessary to use plexiglass as a work item. You can apply the tree, but there will be a problem with the change of abrasive paper. The tree must not be constantly wet. The bar can swell and lose shape, so masters prefer plexiglass.
On the proposed video, one of the options for a grinding machine:
Sharpening various cutting tools
In the household, in addition to ordinary knives, there will always be tailor, office and manicure scissors.
With a slight improvement in the attachment for knives, you can fix the scissors on the platform of the machine. Updating old tools with dull cutting edges is a problem that is always relevant and needs to be addressed.
Alternative
If the farm does not need a special filigree sharpening of cutting tools, you can do it with a home-made electric sharpener. To make the device, an electric motor is required. The engine from the old washing machine is quite suitable for a sharpener.
In the nearest workshop you can order special bushings for fastening the emery and grinding wheel on the motor shaft. An ideal solution would be to install a transformer that regulates engine speed.
Electric sharpener can be bought in a distribution network. The factory-made device has two circles on the shaft on either side of the motor. Without changing the circle, you can sharpen the knife and polish the chamfer of the blade.
Professional machines
Such equipment is installed in workshops for the production of cutting tools. Knife blanks are processed on planing machines.
High-strength cutters form a chamfer of metal from metal. Finally, the knives are finished on aggregates with grinding wheels.