Cutting fluid -Types, Properties & function

This post describe about Cutting Fluid,properties of cutting fluids,function of cutting fluid and types of cutting fluids.

Cutting Fluid:

During the metal cutting process, heat is generated due to plastic deformation of metal and friction of tool workpiece interface. This will be increase the temperature of both workpiece and tool. Hence, the harness of tool will be decreased. This lead to tool failure. Cutting fluid are used to avoid heat production during the machining process. At the same time, it reduce the friction between tool and chip. The cutting fluid usually in the form of liquid applied to chip zone to improve the cutting life or condition.

Function of cutting fluid in Machining:

  • The cutting fluid cool the tool and workpiece. When the heat produced during the machining operation is carried out by the fluid. It done by supply adequate quality of cutting fluid. It is necessary to cool the tool to prevent metrological damage and assist in decrease friction at the tool and workpiece interface. When the friction will be decreased, the life of tool will be increased and also the surface finish of work will be improved. The cutting fluid is prevent the workpiece from excessive thermal distortion.
  • The cutting fluid lubrication of cutting tool and reduce the coefficient of friction in between work and tool. That property will be reduce the energy or power consumption in metal removal. So, the wear on the tool is reduced and the tool life will be increased.
  • The cutting fluid improve the surface finish as stated earlier.
    It courses the ship to break up into small parts. It protect the surface finish from corrosion.
    The cutting fluid washes away chip from the tool. That help to prevent the tool from foulings.
    It also prevent corrosion of machine and work.

Common Properties of cutting fluid:

  • High heat absorbing capacity
  • High flash point
  • Non corrosive to tool and work material
  • It should be harmless to operate and bearing
  • It has good lubrication properties to reduce frictional force and to reduce the power consumption
  • It having high heat conductivity, high specific heat and high film coefficient
  • It should be having odorless
  • In left in air is stable to not get oxidized or decomposed
  • It has transparent, so the cutting action of tool maybe observer. It especially desirable in precision work
  • It should not stain or live residues on surface of work.
  • It Should be used in economical condition

Types of cutting fluids:

The different types of cutting fluid used depends upon machining method characteristics and work material.They are basically two main types of cutting fluid,

  • Water based cutting fluid
  • Straight or heat oil based cutting fluid

Water based cutting fluid:

To improve the cooling and lubrication properties of cutting fluid such as water, the Mineral oil or soft soap could be added it. It is known as soluble oils. Soluble oil are emulsion composition of around 80% of water and remaining soap or Mineral oil. The shop act as emulsifying agent which break the oil in to minutes particles to disperse them throughout water. The water based cutting fluid are mostly used for quit commonly. That should be having excellent cooling properties at low cost and there is also some lubricating effect in between chip and tool which reduce the tool wearing. By mixing of various property of water with soluble oil and soap,to get cutting fluid with wide range of cooling and lubrication properties. For modern, soluble oil having contain corrosion inhibitor and biocide to keep down the growth of bacteria. Frequently used water based cutting fluid based on chemical solution. When the grinding operation process the soda solution are used as it have good flushing and cooling effect. The water used as coolant in small industry or laboratory but it causes rust and corrosion.

Straight or heat oil based cutting fluid:

Straight oil based cutting fluid mean undiluted or pure oil based fluid. Nowadays, most of oil are not directly used in industry but mixing of other oil or oil with chemical such as Sulphur and chlorine. It is classified as below,

  • Mineral oil
  • Chlorinated oil
  • Mixed oil or compounds oil
  • Straight fatty oil
  • Sulphurised oil

Mineral oils

There are primarily composed of hydrocarbon of different structure and Molecular weight. Some example of straight Mineral oil (Petroleum), kerosene and paraffin low viscosity petroleum fraction such as mineral seal or higher viscosity Mineral oil. This types of oils generally used for light machining operation like as turret and capstan lathe and single spindle automatic. When the machining of free cutting brass and Steels.

Straight Fatty oils or fixed oil

This types of oil consist of animal, vegetable and fish oil. Some most commonly used Mineral oil are olive oil, Lard oil, whale oil, lined and cottonseed oil. The most important variety of straight oil is lard oil. This types of oil are not stable and rapidly loose their lubricating property. For thread cutting operation purpose the lard oil is most commonly used. The are more expensive and less available than Mineral oil.

When diluted with 75% Mineral oil. So, there are get with much cheaper and more fluid  than straight fatty oil. This types of oil having excellent lubrication and cooling property.It used for  heavy duty operation, automatic screw machine work such asthread milling, capstan and turret lathe etc.

Sulphurised oil:

It is a one type of chemical addictive oil. This oil has sulphur (about 5%)  is mixed with Lard oil. It oil will give good lubricating and cooling quality. This types of oil is known as sulphurised oil. It is used for gear cutting, thread grinding and heavy duty lathe work.

Chlorinated oils:

It is your another one type of additive oil.To prepare chlorinated oil, chlorine about 3% is added to Mineral oil. There are particularly effective in promoting  anti-wild characterartists.

If use of both chlorine and sulphur with Mineral oil,cutting the extreme pressure property and suitable for  Chevrolet cutting operation at long and tough material such as Stainless Steels and Nickel alloys.

The selection of cutting fluids depends upon following factors,

  • Feed rate
  • Tool and workpiece material
  • Velocity of cutting fluids
  • Life of cutting fluids
  • Cutting speed
  • Depth of cut
  • Tool life to be expected
  • Economical aspects


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