Types of Straight or Neat Oil-Based Cutting Fluid

🔗Functions and advantages of cutting fluid in metal machining
🔗Water-based and Straight oil-based cutting fluid

When oil is the main constituent of cutting fluid (without dilution with water) then it is called straight oil based cutting fluid. This type of fluid classified based on the additives added to it. Some type of straight oil cutting fluid is listed below

Mineral oil

Mineral oils are generally used in light cutting operations. This oil mainly composed of a hydrocarbon of different structure and molecular weight. Mineral oils are used in machining of free cutting brass and steels in turret and capson lathe, and single spindle automatics.

Straight fatty oils

These type of oils are expensive than mineral oil. They have a high viscosity so they do not consider as good coolant. These oil are not stable and they lose their lubricating properties very rapidly. General example for straight fatty oil is lard oil used in thread cutting with taps and dies.

Compound or blended oil

Blended oil is a mixture of mineral oil and fatty oils. They are suitable for medium capacity automatic lathes and heavy duty matching operation like thread milling, threading on capstan and turret lathes. One of the advantages of this types oil is that fatty oil retains its film strength even when diluted with 75% mineral oil. So they are cheaper than the straight fatty oils.

Sulphurised oils

In this type oil, sulphur is added to other type oil to facilitate heavy duty works. For example, sulphur (about 5%) is added to lard oil to perform heavy duty lathe work, thread grinding, gear cutting etc. when sulphur is added to mineral oil then it is called as extreme pressure (E.P.) cutting oil. Depending on the form of sulphur, the extreme pressure cutting oil is mainly divided into three
1. Oil containing free sulphur
2. Oil containing combined sulphur
3. Oil containing both free and combined sulphur.

Active oils and inactive oil of extreme pressure oil
The extreme pressure (EP) oil containing free sulphur (first and third type) stain yellow metal, so they are called active oils. The EP oil which only has combined sulphur in it (second type) is called inactive oil since it does not stain yellow metal.

Chlorinated oil

When mineral oil contains about 3% chlorine in it then called chlorinated cutting oil. In some cases chlorine added to mineral oil along with sulphur, such oil shows extreme pressure oil properties and they used for severe cutting operation on tough material like nickel alloys. These type oil also preferred in broaching operation.