Cutting Fluids ... Do you REALLY think about them?

Another major factor to be considered with good Chip Making is the cutting fluids employed. In this post ... we are dedicating some facts and ideas to probably one of the least considered factors in Making Chips.

Cutting fluids typically perform numerous functions simultaneously, including cooling the workpiece and cutting tool, lubricating, minimizing the effects of built-up edge, protecting the workpiece from corrosion, and flushing away chips. The success of cutting fluids is dependant on a combination of interacting parameters, such as cutting fluid formulation, workpiece material, tool material and tool geometry, surrounding atmosphere and cutting speed. Machine design is also of increasing importance.

Cooling Mechanism

Two requirements must be met in order for a cutting fluid to function effectively as a coolant . The fluid must gain access to the course of heat, and the fluid must have the capability of removing the heat.

Lubricating Mechanism

High pressures and temperatures in most cutting operations make it impossible for a cutting fluid to sustain a complete liquid film between the cutting tool and workpiece material. Instead, the conditions in a typical metalcutting operation favor the use of the fluid primarily as a boundary lubricant. In boundary lubrication, additives in the fluid react chemically with the workpiece material and tool material to form compounds on the metal surfaces. One theory suggest that lubrication in cutting occurs by a reduction in severity of shear strain at the cutting tool. Two schools of thought exist to support this theory. First, the lubricant absorbs into the chip surface and restricts the adhesion of chip material to the tool. Second, the reactive components of the fluid combine chemically with the freshly generated metal surface of the chip to produce a film which has a lower shear strength than that of the chip material, thus reducing friction, cutting forces, and temperature.

Corrosion Protection Mechanism

Corrosion protection of the machine tool and workpiece is important when machining operations employ the use of a cutting fluid. Some lubrication charecteristics to consider when looking at the composition of cutting fluids :

Soda Ash -- increases the alkalinity of the fluid and reduced the tendency to cause rust.

Mineral Oils -- provide a major deterrent to rust formation using an ability to coat the surfaces of the machine tool and workpiece to form a physical barrier to prevent chemical reaction from taking place.

Chip Removal Mechanism

In machining operations that generate large amounts of metal chips, an important function of a cutting fluid is to flush chips away from the cutting zones. The flushing action removes the chips from the cutting zone and keeps them from scratching the machined surfaces. This action is especially useful in deep-hole drilling, trepanning, and gundrilling operations, in which fluid is used to force the chips out of the hole. One major consideration in these applications is the pressure under which the fluid is supplied to the cut. However, with these applications can come excessive foam generation which can weaken the effects of the cutting fluid. Proper selection of cutting fluid is important to avoid this condition which can interrupt the machining and cutting fluid filtering process.

Information in this article was taken from Kentech's KipwareEDU® - Mechanical Engineering Version. If you found this information helpful ... we invite you to explore all our versions of KipwareEDU® ... just click here.