Cutting Oil
The Industrial Revolution bought with it many changes. One of those changes was the way that metals are worked. Instead of relying on a man's strength to shape metal, there were now machines that were able to cut and shape the metal for you. But with the new technology came new problems, like how to cool and lubricate the cutting tool, extend its life and improve surface finish. The answer to this problem was, of course, to use cutting fluids including cutting oils.

What are Cutting Fluids?
Cutting Fluids serve as a combination of coolant and lubricant and were created specifically to be used for machine work and metalworking. Cutting fluids typically fall into one of the following categories; oils, pastes, gels, oil-water emulsions and mist and are made out of plant oils, animal fats or petroleum derivatives.

The process of cutting and working metal by machine produces a great deal of heat; metal on metal, and one of a cutting fluid's main objectives is to keep the piece being worked on at a consistent temperature. Beside servicing as coolants they also prolong the life of the cutting tool by reducing friction and help to reduce any safety risks to the person handling the machine and material and reducing rust on the machine parts.

The History of Cutting Fluids
When cutting fluids first started being used water was the most logical choice, for with the heat and friction caused by metalworking the first instinct was to cool it off with water. It was quickly found, however, that water made the metal machine parts rust fairly quickly. Soda water was the next step, and helped with the rust problem though it did not do much for lubrication. When someone actually figured that putting grease on the machine parts would help, lard became the lubricant of choice. There are references as well to red and white lead being mixed into lard oil to make it more malleable, but that practice was discontinued due to the discovered toxicity of lead.

Today cutting oils fall into four basic categories;

1. Straight oils, which are used for machines that run at a slower speed and need more lubrication than cooling.

2. Soluble oils, which have additives that allow them to be mixed with water. These not only provide lubrication but some cooling.

3. Semi-synthetic oils, which are similar to soluble oils but contain less petroleum, making them cleaner and more effective as coolants

4. Synthetic oils, which contain no petroleum based oils and are the best for performance, cooling and rust prevention.

Application and Safety
All four of these categories are applied in any number of ways, including dripping; spraying, misting, brushing, whatever suits the purpose at hand, though direct contact with any cutting oil should be avoided due to the fact that many have been linked to skin rashes, esophagitis, lung disease and even cancer.