The tremendous amount of heat generated during the cutting, grinding, and boring of metal parts must be cooled down to prevent burning and smoking. Lubrication is also necessary to reduce friction between the machined part and the tool, resulting in improved surface finishes and extended tool life. That’s why selecting the right machining oil or metalworking fluid is so important.

Machining fluids have two primary functions: to cool and to lubricate. They further protect the tools and newly machined parts from corrosion by removing chips from the cutting zone. Below, we discuss the major types of machining oils, their specific uses across various industrial applications, and where to look to find precision-cut metals that meet your requirements.

Types of Machining Oil and Their Uses

Viscosity, or the measure of an oil’s resistance to flow, is an important property that determines the suitability of a machining oil for industrial applications. Viscosity decreases with increasing temperatures and can affect heat generation during cutting, grinding, milling, or other operations. For the most effective lubrication, the viscosity of a machining oil should conform to the temperature conditions, speed, and load of the lubricated parts.

Based on the material being machined, cutting tools and conditions, and the required level of accuracy and finish, different formulations of machining oils are used. For example, in high-speed machining with easier-to-cut metals, machining oils featuring greater cooling capabilities are used to address intense heat generation. Machining oils with greater lubricity are more suitable for low-speed machining with difficult-to-cut materials.

The following are a few of the major categories of heavy machining oils (also known as cutting and grinding fluids).

Straight Oils

Made up of petroleum (mineral) or vegetable oils, these fluids have a viscous feel and oily appearance that make them more suitable for lubrication instead of cooling. Commonly used for  high metal-to-metal contact situations at slow-cut speeds (particularly with older machines), straight oils are not diluted with water before use and may contain sulfur or chlorinated additives. The wetting action and lubricity of straight oils can be further increased by adding other oils of animal, marine, or synthetic origin.

Soluble Oils

Soluble oils are mostly better at cooling and lubrication when compared to straight oils. However, soluble oils sometimes display poor corrosion control. Made from severely refined lubricant base oil (between 30-85%), a soluble oil also contains emulsifiers and other additives to help disperse the oil in water and improve the performance of the fluid. The soluble oil concentrate is diluted with water to transform it into a working fluid.

Semi-Synthetic

A lower amount (between 5-30%) of severely refined lubricant base oil in the concentrate makes semi-synthetics ideal for heat reduction, rust control, lubrication, and longer sump life. Though containing many of the same components as soluble oils, semi-synthetics are cleaner.

Synthetic

Synthetics do not contain any petroleum oil in their composition. Among the heavy machining oils, synthetics are known to be the cleanest, offering excellent heat reduction, rust control, and prolonged sump life. As a class of water-miscible fluids, synthetics must be diluted with water to produce machining fluid and are largely unaffected by hard water.

Machining Oil Considerations

Your choice of machining oils for heavy-duty industrial operations depends on a number of factors, including the type of metal, cutting tool material, fluid properties, and other variables. A soluble oil with a consistency of 1 part oil to 10-20 parts water works well for ordinary drilling, boring, milling, and turning on medium and low-strength steels. For turning and milling tough-alloy steels, a soluble oil with a consistency of 1 part oil to 10 parts water is more suitable. A sulfochlorinated mineral fatty oil is recommended for tough machining operations such as threading, tapping, or broaching tool steels and high-strength steels.

For many small machining and fabrication shops, determining the right machining oil for various heavy-duty operations can be a challenge. A cost-effective alternative is to partner with an experienced team of professionals with quality sawing resources to address your metal-cutting requirements.

Sourcing Your Metal Sawing Requirements from a Trusted Supplier

At Industrial Metal Service, we’ve been helping our clients in the San Francisco Bay Area and beyond for more than two decades. Our proprietary Amada PCSAW 530 X band saw with pulse cutting technology can cut specialty metals such as titanium with unmatched precision. And our MetlSaw NF12-T12 easily cuts large, non-ferrous metals up to 12 feet long and 12 inches thick with tolerances up to ± 0.065″. With innovation and reliability serving as the cornerstones of our operations, reducing material wastage and helping businesses cut down on costs are always our priority.