In industries that follow traditional production methods, no other segment plays a role as crucial as machining process. It is not only the backbone of such industries, but also the segment which involves the bulk of production costs.
The most defining aspects of machining processes are the cutting tools and work piece materials used, so manufacturers are constantly on the hunt for cost-effective options.
During machining process, friction between the interfaces of the workpiece-cutting tool and cutting tool-chip raises the temperature of the cutting tool. This reduces the lifespan of the tool, makes the surface rough, and decreases the dimensional sensitiveness of the work material. To deal with this, cutting fluids are used in all machining processes.
A cutting fluid has three properties:
• Cooling effect;
• Lubrication effect; and
• Taking away formed chip from the cutting zone
Of the three, the cooling effect is the most sought, as a reduction in temperature directly reduces tool wear and increases the accuracy of the workpiece and the lifespan of the cutting tool.
The lubrication effect makes it easier for the chip to flow on the rake-face of the cutting tool. When machining aluminium and aluminium alloys, lubrication decreases the build-up of edges, resulting in more desirable surface roughness.
The type of cutting fluid used depends on three factors:
• type of machining process;
• type of machined workpiece material;
• type of cutting tool material.
The most important parameter while selecting a metal working or cutting fluid is the machining process used. The more complex the machining process, greater the amount of cutting fluid needed. Machining processes such as grinding, cutting with saw and turning require lesser amount of cutting fluid; on the other hand, complex processes such as gear production, screwing and broaching require a higher amount of cutting fluid. In addition, heavy processes (like broaching) require heavy cutting oils.
Sometimes, only one property of a cutting fluid is required. For example, in a threading process, the interface between the cutting tool and the workpiece is small, but the interface is continuous. For this operation, the cooling property of the cutting fluid is used.
The type of workpiece material is also an important factor in choosing a cutting fluid. For steel machining operations, high pressure and additive cutting fluids are used. For machining heat resistant, resilient steel alloys, water-based cutting fluids are preferred.
The third factor that determines the type of cutting fluid used is the material of which the cutting tool is composed. A number of cutting tool materials is commercially available for all kind of machining processes. All types of cutting fluids are suitable for high speed steel cutting tools. For cutting tools made of tungsten carbide, cutting fluids with strong cooling properties are preferred, because tungsten carbide is highly conductive to heat.
Cutting tools made of cubic boron nitrate and polycrystalline diamonds have found an important place in the machining process industry. However, these are expensive and used only to obtain high dimensional accuracy and excellent surface finish quality.
Witmans Advanced Fluids (WAF) offers a vast range of cutting oils designed to meet all kinds of machining processes, workpiece materials and cutting tools. Their products are formulated with painstaking attention to quality. WAF works on a joint venture with Lubritalia of Italy to bring about innovations in oils and lubricants for the steel industry.