Cutting Fluid Applications and Functions

Cutting fluid may be applied to a cutting tool/workpiece interface through manual, flood or mist application.

Manual application

simply consists of an operator using a container, such as an oil can, to apply cutting fluid to the cutting tool/workpiece. Although this is the easiest and least costly method of fluid application, it has limited use in machining operations and is often hampered by inconsistencies in application.

Flood application

delivers fluid to the cutting tool/workpiece interface by means of a pipe, hose or nozzle system. Fluid is directed under pressure to the tool/workpiece interface in a manner that produces maximum results. Pressure, direction and shape of the fluid stream must be regulated in order to achieve optimum performance.

Mist Application

Cutting fluids may also be atomized and blown onto the tool/workpiece interface via mist application. This application method requires adequate ventilation to protect the machine tool operator. The pressure and direction of the mist stream are also crucial to the success of the application.

Metalworking fluid used in flood or mist applications is typically stored and distributed utilizing an individual machine tool system or a central reservoir system. Individual machine tools with internal cutting fluid systems consist of a sump for fluid storage, a pump, delivery piping, a spent fluid collection and return system, and a filter to remove contaminants. Coolant recirculates from the machine sump to the machine tool.

Centralized reservoir systems may contain hundreds of gallons of cutting fluid which is distributed to individual machine tools via a pump and piping system. Prior to fluid returning to the central reservoir, it is passed through a filtering system designed to remove contaminants such as metal chips and other particulates.

FUNCTIONS OF CUTTING FLUID

The primary function of cutting fluid is temperature control through cooling and lubrication. Application of cutting fluid also improves the quality of the workpiece by continually removing metal fines and cuttings from the tool and cutting zone.

TEMPERATURE CONTROL

Laboratory tests have shown that heat produced during machining has a definite bearing on tool wear. Reducing cutting-tool temperature is important since a small reduction in temperature will greatly extend cutting tool life. As cutting fluid is applied during machining operations, it removes heat by carrying it away from the cutting tool/workpiece interface . This cooling effect prevents tools from exceeding their critical temperature range beyond which the tool softens and wears rapidly. Fluids also lubricate the cutting tool/workpiece interface, minimizing the amount of heat generated by friction. A fluid’s cooling and lubrication properties are critical in decreasing tool wear and extending tool life. Cooling and lubrication are also important in achieving the desired size, finish and shape of the workpiece. No one particular fluid has cooling and lubrication properties suitable for every metalworking application and we will discuss it in later posts.

REMOVAL OF CUTTINGS AND PARTICULATES

A secondary function of metalworking fluid is to remove chips and metal fines from the tool/workpiece interface. To prevent a finished surface from becoming marred, cutting chips generated during machining operations must be continually flushed away from the cutting zone.

Application of cutting fluid also reduces the occurrence of built-up edge (BUE). BUE refers to metal particulates which adhere to the edge of a tool during machining of some metals. BUE formation causes increased friction and alters the geometry of the machine tool. This, in turn, affects workpiece quality, often resulting in a poor surface finish and inconsistencies in workpiece size.

Metalworking fluids decrease the occurrence of BUE by providing a chemical interface between the machine tool and workpiece.

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