Water or oil is used with a special whetstone for blade sharpening. The liquid is applied to the sharpening stone or bar before sharpening. Below we will analyze the purpose of the cooling liquid, the order of actions during sharpening and how to choose the material.
Why do you need oil for sharpening
During sharpening, the stone removes tine metal particles from the blade. Pressing the blade against the rough surface results in increased friction. Due to this the metal surface temperature goes up. The knife sharpening oil allows:
- To eliminate the risk of rapid corrosion. Unlike water, oil does not oxidize metal parts. Therefore, there is a lowr risk of corrosion spreading.
- To reduce friction. The thin oil film on the surface helps to avoid large scratches on the cutting edge. Therefore, the cooling liquid is perfectly suited for finishing.
- To prevent the stone from getting clogged. The oil draws the burrs away from the contact area between steel and stone. This means that you will not have to clean the sharpening stone as often.
- Reduce the temperature. Overheating of steel leads to changes in its physical properties. Cooling liquid helps to keep the blade cool, even during heavy work.
Besides, during sharpening, the stone surface produces a slurry that consists of a liquid and an abrasive residue. The slurry provides the best possible sharpening results.
What oils can you use for sharpening
There is a wide range of oils available. Therefore, it is quite difficult for a beginner to make up his mind about the choice of a cooling liquid. Here is a list of oils that can be used to work with a blade:
- Plant-based edible oils. Olive, peanut, rapeseed oil, etc. Bear in mind that such liquids are highly viscous and can lead to clogging of the sharpening stone surface.
- Technical. Such oils are made through petroleum refining. Some use a spindle oil for sharpening due its low viscosity. Keep in mind, that machine oils can have various additives in their composition. Due to this, it is better to choose a mineral oil.
- Gun oils. Sometimes people use ballistol for sharpening their knives. However, one should bear in mind that, just as with technical oil, this is not a food-grade product. The blade must be thoroughly cleaned after sharpening.
- Vaseline oil. This product is made through the petroleum refining process. The liquid is purified from harmful substances. Be aware that this oil has an increased viscosity. Therefore, it will be difficult to use it in its pure form for sharpening.
- Camellia oil. This oil has no smell, so it is comfortable to work with. Camellia oil is good for both sharpening with an abrasive whetstone, and for protecting the blade from corrosion. A thin film remains on the surface after treatment, preventing the steel from coming into contact with oxygen. Therefore, the risk of metal oxidation is minimised.
- Special sharpening liquids. Cooling liquids based on water and oleic acid are designed for blade treatment. They are non-harmful to human health and provide quality processing due to low viscosity. Besides, some compositions are used both for sharpening and cleaning sharpening stones from contamination. This explains the widespread use among beginners and professional sharpeners.
Special sharpening cooling liquids are the best option. They ensure maximum sharpening quality of the cutting edge, reduce the metal heating and remove fine particles from the contact area between steel and stone.
How to use oil with a sharpening stone
The sharpening oils work with natural stones, diamond coated bars or aluminium oxide sharpening stones. They can also be used with stones designed for use with a sharpener, such as a TSPROF sharpener. How to work with oil:
- Clean old metal particles from the abrasive stone surface. Contamination on the surface blocks the normal removal of metal from the cutting edge. That is why it is super important to clean the stone before work. You can use special cleaning liquids for this.
- Secure the abrasive stone. Place the abrasive element on a stable surface. A workbench, table or other object with a horizontal plane would be best. Do not sharpen on an shaking surface, this may result in injury. Some manufacturers sell oil stones on special stands. This helps to prevent the abrasive stone from moving during sharpening.
- Apply the cooling liquid to the stone surface. Just a few drops for a thin film on the surface will be enough for work. You can apply the oil with a pipette. Special liquids designed for sharpening come with a dispenser. This facilitates the applying process.
- Hold the knife at the desired angle and run it across the stone on the cutting edge. At this stage it is vital to keep the required angle and maintain the same pressure on the blade. This will affect the sharpening quality. Repeat the same steps several times for both sides At this stage, you will remove small metal particles from the cutting edge.
- Replace the stone with a finer abrasive stone. The finishing process requires a stone with a minimum roughness. This will make the cutting edge razor sharp. A fine abrasive stone removes large scratches and grooves, which increases the sharpness of the cutting edge.
- Remove small abrasive particles and oil residues from the blade. To clean the blade from specially designed sharpening compounds, it is enough to wipe it with a clean rag. To remove technical oil from the surface, you will need to wash it under running water.
After work, you should clean the abrasive stone from any dirt. Remove oil residue and small steel particles that have got into the abrasive stone's surface during the sharpening process. Breaking this rule will lead to rapid clogging of the stone surface.
How to choose the sharpening oil
Given the wide range of cooling liquids, it can be difficult for a beginner to make a choice. This is caused by the fact that the oil must meet several requirements at the same time. Only then can you achieve maximum sharpness. To choose a cooling liquid you need to pay attention to:
- Purpose. Oil can have different effects when used with diamond stones, natural stones or other abrasives. Therefore, when you choose a special liquid, you should take into account its intended operating conditions.
- Viscosity. This parameter determines the ability to remove small abrasive and metal particles from the stone-blade contact area. The cooling liquid should not be viscous. Use of a thick oil will lead to dirt gathering in one place on the surface and will result in worse sharpening quality.
- Drying rate. Sharpening blades requires liquids with the longest drying period. This will reduce the oil consumption and will shorten the time required for sharpening. The longer it dries the less often you will have to apply it to the surface.
- No toxic fumes. When you sharpen a knife, you stay in close proximity to the knife and the sharpening system. Toxic fumes coming from the abrasive dust can be harmful to your health. For this reason, you should pay attention to the composition of the cooling liquid.
- Safe if it gets inside your body. When you finish sharpening, there will always be a small amount of cooling liquid left on the steel surface. If it is harmless to human health, it is enough to remove it with a rag. If it is dangerous to human health you will need to do a proper cleaning.
Based on the above criteria, the best option is to use oils specifically designed for sharpening. They are safe for health and ensure that the blade will be as sharp as possible.
What to use instead of the specialised liquid
If there is no specialised sharpening liquid available, you can choose a material that meets the requirements given above. However, you should bear in mind that this would make it difficult to achieve a maximum level of sharpness.
If you choose a machine oil, you better settle on a spindle or hydraulic mineral oil. Such compounds have minimum additives that can be harmful to human health.
You can also use oleic acid. It ensures maximum processing quality. Harmlessness, low viscosity and slow drying speed allow this material to be used as a substitute for special liquids.
Some use castor oil as a substitute. However, keep in mind that this material is highly viscous. Therefore, it can cause clogging of the sharpening stone.
Using sharpening liquids will help you make your knife as sharp as a razor. This prevents the steel from coming into contact with water, which reduces the risk of rusting. With the right oil, the sharpening process will be both convenient and fast. The best option will be the use of specialised liquids. However, if you do not have the necessary compound at hand, you can use other lubricants.
While manual hand sharpening is a universal method, consider using a manual precision sharpener — and sharpening with any oil will seem like a breeze, thanks to the fixed knife position and fixed sharpening angle.
