How to sharpen a knife



Proper sharpening will reveal the best features of your knife, make an accent on the blade beauty and quality of the steel – the knife will stay sharp for a long time, the cutting edge will not be crumbled due to increased load.
 

A minimal kit of the instruments for the proper knife sharpening

Minimal Kit of the instruments

 
 — Abrasives (whetstones, blocks, plates, chisels). The choice of it for the knives of the different purposes and steel hardness described in the article in detail. A few tips of the choice of the abrasive are given in the next paragraph
—Oil and water for wetting of the abrasive stones. Are necessary to avoid the scattering of the metal dust during sharpening and clogging of it into the pores of the stone.
- Masking tape or PVC tape to protect the blade from scratches.
- Digital protractor for the desired sharpening angle setup. At worst, you can use a sheet of paper for these purposes.
- Magnifier with a magnification of 10x or a non-woven cloth to check for burrs.
- Running water and soap for washing stones.

Chose the abrasive





For sharpening you will need a set of 3-4 abrasives of different grain sizes (indicated in grit according to the FEPA standard):
 
1. Extra Coarse 120-180 for the formation of the edge.
2. Coarse 220-400 to reach the angle.
3. Medium/Fine 500-800 for the final output of the angle.
4. ExtraFine 1000-1200 for sharpening therazoredge.
 
 
The choice of the abrasive material must be based on the hardness of the blade, the purpose of the knife and financial capabilities.
 
Aluminum oxide abrasives are well suited for mild steel knives - hardness below 58 HRC (Rockwell hardness) - these are knives for which flexibility is important. For example, hunting skinning knives, poultry cutting knives, chef knives.
 
Aluminum oxide abrasives show low productivity with steels of 59 HRC and higher (knives designed for high loads and aggressive cutting, for example, for cleaning and skinning of large animals) Silicon carbide abrasives work best with such steels.
 
Diamond abrasives - suitable for powder steels, mono steels (steels with a uniform chemical composition), hardened for high hardness. Diamond sharpening usually gives an aggressive cut and good durability, therefore it is often used for hunting knives. It is possible to work with diamond abrasives on soft stainless steel, but the wear of the stone, in this case, will be higher. Such abrasives are more expensive, but they provide the desired level of sharpening faster, retain their shape and properties longer. Be careful - the grain size of diamond abrasives is indicated in microns.
 
Prepare the knife before sharpening




 
 
Tape the knife blade with masking tape leaving the cutting edge free. This will protect the blade from scratching during sharpening.
You can sharpen the knife in your hands if you are sure that you can hold the angle consistent. If you are not sure that you can maintain the correct angle and the knife will not “free play” - use a special device to fix the knife and to achieve the desired angle.
If you want to be completely confident that you will protect the knife from damage caused by the abrasive accidentally torn off the cutting edge, use the stroke limiters for sharpening stones, the same as the limiters of TSPROF Sharpener.
 
Choose the sharpening angle for your knife


 

Typically, the sharpening angle is between 15-25 degrees by the side.

For sharpening knives made of hard steels, designed for high loads (cleaning and skinning a boar, cutting wood, ropes, leather), choose an angle of 21-25 degrees by the side –it will help avoid crumbling of the cutting edge during usage.
 
Choose an angle of 18-20 degrees by the side for the sharpening of the knives for delicate work (cutting a bird, thin chopping)
 
Use the digital protractor to determine the desired angle. If you don’t have a protractor, bend a sheet of paper diagonally 2 times. The first time you get an angle of 45 degrees, the second - about 22 degrees.
In order to avoid problems with setting and maintaining the desired angle, all sharpening devices of the TSPROF are equipped with a mechanical angle gauge with an accuracy up to 1 degree. If you like the perfect accuracy - use a digital protractor. It allows you to set the angle with the precision up to 0,1 of degree.


Sharpen the knife. Control the burr



 
Stage 1 - grinding

You need a "grinding" if you want to change an angle of the cutting edge, fix a damaged or sharpen the completely dull blade. Start the grinding with an extra coarse grain abrasive (120-180) previously wetted with water or oil.
 
Usually, stones with the ceramic, organic, magnesium bonds are working with the water (they must be lubricated with clean water and a soap-water solution, or even soaked in water before sharpening for 10-15 minutes). Metal bonded diamond stones, Arkansas, synthetic resins bonded stones are often worked with water. Some diamond abrasives and abrasives made from natural stones are used “dry” - without the grease or moisture.
There are many nuances and exceptions. For example, Norton India stones are ceramic bonded and designed for oil lubrication.
Therefore, the choice of the lubricant should be based on the recommendations of the abrasive manufacturer.
The abrasive should move across the cutting edge (not along!) during sharpening.
The appearance of a burr on the back of the cutting edge will show the fact that you have worked well enough. A burr is a thin, rough layer of metal that appeared along the edge. It can be seen using optics (magnifier from 10x), felt with your fingers or checked with a non-woven napkin - if there is a burr, it will catch a napkin while moving along the cutting edge.
 
After the burr appears, turn the knife over and start sharpening another side. With the same sharpening movements, remove the burr to another side.
Be careful removing the previous burr. Sometimes it just moves to another site, and if you turn the knife over too early the quality of the sharpening will suffer.

Stage 2 - angle establishment


Repeat the steps from the first stage with an abrasive with smaller grain size (220-400 grit).
If you need an aggressive cut - go to stage 3, “razor sharpness” sharpening - repeat the steps from the first stage again, but with an abrasive of 500-800 grit).



 

Stage 3 - Final Sharpening


With the finest grit (500-800 grit - for an aggressive cut or 1000-1200 grit for a “razor” sharpening), completely remove the burr: make 4-5 sharpening movements on each part of the cutting edge on one side, turn the knife over and make 3- 4 movements on each part of the cutting edge, on the other hand, turn over again and make 2-3 movements. Thus, bring the number of movements to 1. Done - the burr is removed.

Do not forget to support the tip of the knife with your finger during sharpening to save it from crumbling due to the abrasive pressure.
 
Rinse abrasives and knife
Be sure to wash the abrasives with soap and water - this will eliminate clogging with metal dust and oil and will help the abrasive to last longer.
Wash the knife blade with a spray bottle and wipe with a soft cloth.

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