Mist collector technical information 1-3. Types of cutting oil
1-3. Types of cutting oil
This section describes the types of cutting oils available and the characteristics and classification of each type of oil.
(1) Water-insoluble cutting oil and water-soluble cutting oil
Cutting oils can be broadly divided into water-soluble and water-insoluble cutting oils
As briefly mentioned previously, cutting oils are broadly divided into water-insoluble cutting oils that are used without diluting them in water and water-soluble cutting oils that are used by diluting them in water.
Characteristics of water-insoluble oils
- Suitable for light cutting non-ferrous and other metals that are easily corroded.
- They suppress the built-up edge because of their excellent lubricity and anti-welding properties and thus they are suitable for the processing of alloy steels and difficult-to-machine materials where precision is required.
- Handling precautions are required when cutting or storing because the oil is flammable. These are subject to the Fire Services Act.
- Oil mist countermeasures are required to prevent oil fumes from being generated at high temperatures.
Characteristics of water-soluble oils
- Suitable for cutting at high speed with its high cooling effect.
- Rust prevention measures are required for workpieces and tools etc.
- Control requires countermeasures to prevent decay and degradation due to bacteria etc.
- Suitable for unmanned factories as they are non-combustible. These are not subject to the Fire Services Act*.
- High cost performance as they can be diluted with water.
*Not all water-soluble oils are subject to the Fire Services Act.
(2) Characteristics and classification of water-insoluble cutting oils
Components are base oil + additives
The main component of the base oil is mineral oil, but it is also composed of other synthetic oils and fatty acids.
What is a mineral oil?
It is an oil component in which crude oil is purified by compression and distillation to remove the impurities etc. It has a fluid lubricating performance, allowing machining to be carried out with just the mineral oil alone if the cutting is light.
What is a synthetic oil?
Also known as a synthetic lubricating oil, it is a chemically synthesized compound used to supplement the performance that mineral oil does not have. Excellent lubricity.
What are fatty acids?
Also known as fats, these are liquids at room temperature. Rapeseed oil, castor oil, palm oil, etc. are used. They are used widely as they are biodegradable and thus environmentally-friendly.
Additives are used to restore or supplement the performance of base oils, or to impart a specific performance to them.
Classification by JIS standards
Water-insoluble oils are classified from “N1”to “N4” depending on whether they contain any hypoid additives and copper plate corrosion.
Hypoid additives are additives that increase the strength of the oil film between the friction surfaces, reduce friction and wear, and prevent the lubrication surface from being burned.
In addition, the copper plate corrosion level is determined by testing the corrosivenesss of a copper plate, with “1” being “slightly discolored”, “2” being “moderately discolored”, “3” being “heavily discolored”, and “4” being “corroded”.
| Hypoid additives | Copper plate corrosion | Mineral oil proportion | Application | |
|---|---|---|---|---|
| Oil-based type N1 poles (No. 1 - 4) |
Without | ― | 60～95％ | Processing of cast iron and non-ferrous metals and copper |
| Inert hypoid type N2 poles (No. 1 - 4) |
With | Less than 2 at 150 °C | 30～95％ | General cutting |
|
Inert hypoid type |
With (including sulfur content) |
2 or less at 100 °C 2 or more at 150 °C |
30～95％ | General cutting Heavy cutting Cutting of difficult-to-machine materials |
| Active hypoid type N4 poles (No. 1 - 8) |
With (including sulfur content) |
3 or more at 100 °C | 30～95％ | Heavy cutting Cutting of difficult-to-machine materials |
In addition, “N1” to “N4” is further subdivided according to the sulfur content, fat content, and kinematic viscosity into No. 1 to 4 for “N1” and “N2” and No. 1 - 8 for “N3” and “N4”.
(3) Characteristics and classification of water-soluble cutting oils
“Water and oil” are mixed with a surfactant
Water-soluble cutting oils are a mixture of “water and oil” that have been bonded together using a surfactant even though they essentially cannot be mixed together.
A “boundary” is created by the surfaces of two materials with different properties, and a boundary exists between water and oil too.
Surfactants are substances that act on and change the properties of this boundary. Under JIS standards, they are defined as synthetic substances that emulsify insoluble liquids in water, disperse powders and solids in water, wash away dirt on fibers and metals and so on. For example, familiar goods such as soaps and detergents also contain surfactants.
Classification and general classification by JIS standards
Water-soluble oils are classified from “A1” to “A3” according to their appearance when diluted and the solubility of their components in water. However, generally, they are classified as “emulsion type”, “micro emulsion type”, “soluble type”, or “chemical solution type”.
If the oil-based substance is large even after mixing it uniformly with a surfactant, the solution becomes cloudy and the state is known as an emulsion type. Conversely, it becomes transparent when the oil-based substance is small and light passes through, so it is known as a soluble (melting) type.
| JIS classification | JIS classification | Exterior | Features |
|---|---|---|---|
| Class A1 (No. 1, 2) |
Emulsion-type | Milky white | lubricity is great and effective for low-speed heavy cutting. Less impact on paint and hand roughness too. |
| Micro-emulsion type | Milky white (Slightly transparent) |
||
| (Slightly transparent) (No. 1, 2) |
soluble-type | Transparent Translucent (May be colored) |
High permeability, effective for high-speed light cutting. Impact on paint is great depending on the type. |
| Class A3 (No. 1, 2) |
chemical solution-type | Transparent (May be colored) |
Excellent rust prevention with less decomposition. Impact on paint and hand roughness is slightly larger depending on the type. |
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