CuttingFluids[1] - Cutting Fluids WHAT ARE THE FUNCTIONS OF...

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Cutting Fluids WHAT ARE THE FUNCTIONS OF A CUTTING FLUID ? Primarily, a cutting fluid must contribute in three ways to a machining process. 1. First, it must act as a lubricant. By reducing friction, it reduces the heat generated. 2. Because frictional heating cannot be completely eliminated ± and often, not even substantially reduced ± the cutting fluid must also act as an effective coolant. 3. Finally, it should act as an antiweld agent to counteract the tendency of the work material to weld the tool under heat and pressure. CUTTING FLUIDS AS LUBRICANTS To perform satisfactorily as a lubricant, the cutting oil must maintain a strong protective film in that portion of the area between the tool face and the metal being cut where hydrodynamic conditions can exist. Such a film assists the chip in sliding readily over the tool. Besides reducing heat, proper lubrication lowers power requirements and reduces the rate of tool wear, particularly in machining tough, ductile metals. CUTTING FLUIDS AS COOLANTS If a cutting fluid performs its lubricating function satisfactorily the problem of heat removal from the cutting tool, chip, and work is minimised. But, cooling still remains an important function. To perform this function effectively, a cutting fluid should possess high thermal conductivity so that maximum heat will be absorbed and removed per unit of fluid volume. WHY IS IT THAT WATER CANNOT BE USED AS A CUTTING FLUID ? Water, which has high thermal conductivity and a high specific heat, is a very effective coolant but its lubricating property is practically nil. Moreover, water rapidly corrodes machine parts and components. It can neither lubricate the moving parts of the machine like guides and slides nor can it reduce friction in the cutting area. Also, it is not effective in absorbing heat as it cannot spread well on metallic surfaces. WHAT ARE THE DIFFERENT TYPES OF CUTTING FLUIDS ? ² Soluble Oils ² Synthetic Oils ² Semi-Synthetic Oils ² Straight Cutting Oils SOLUBLE OILS WHAT ARE THE MAIN CONSTITUENTS OF SOLUBLE OILS ? Soluble oil contains : ² Mineral Oil ± Provides lubricity ² Emulsifier ± Breaks oil into small globules ² Rust inhibitor ± Since water can cause rusting ² Bactericide ± To control the growth of anerobic bacteria which causes foul smell and renders oil useless. WHAT IS AN "EMULSION" ? Oil does not dissolve in water. Oil is suspended in water in the form of tiny globules. Breaking of the oils into tiny particles is done by a chemical known as "Emulsifier". This medium of oil in water is known as an "Emulsion". "Specific heat" (ability to absorb heat) and thermal conductivity (ability to dissipate heat) of water is much better than oil whereas "lubricity" (ability to reduce "Friction" ) can be provided only by oil. In a metal cutting operation using an emulsion "oil" provides lubricity and "water" does the cooling. Cutting Fluids
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CuttingFluids[1] - Cutting Fluids WHAT ARE THE FUNCTIONS OF...

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