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Cutting fluids
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Cutting fluids are used to reduce friction, through lubrication, which is a common problem during machining processes, and occurs at the contact between workpiece and the cutting tool.
 
Advantages of using cutting fluid:
  • It keeps the cutting tool cool. thus increase the lifespan of the cutting tool
  • Keep workpiece cool. thus prevent distortion and structural changes to the workpiece material
  • Increase rate of production
  • Give workpiece a good finish
  • Allow for higher cutting speeds and feeds
  • Allow for large cuts
  • Wash away cuttings
  • To prevent corrosion of the work, the tool and the machine
 
Properties of a good cutting fluid:
  • High thermal conductivity for cooling
  • Good lubricating qualities
  • High flash point, should not entail a fire hazard
  • Must not produce a gummy or solid precipitate at ordinary working temperatures
  • Be stable against oxidation
  • Must not promote corrosion or discoloration of the work material
  • Must afford some corrosion protection to newly formed surfaces
  • The components of the lubricant must not become smelly and sticky
  • No unpleasant odour must develop from continued use
  • Must not cause skin irritation or contamination
  • A viscosity that will permit free flow from the work and dripping from the chips
  • Must be chemically stable, event at extreme temperatures
Ideal cutting fluid for specific martial:
 
Material Milling Drilling Tapping Turning
Aluminium Soluble oil (96% water) or mineral oil Soluble oil (70-90% water) 25% sulphur-based oil mixed with mineral oil Mineral oil with 10% fat (or) soluble oil
Brass Soluble oil (96% water) Soluble oil 10-20% lard oil with mineral oil Mineral oil with 10% fat
Bronze Soluble oil Soluble oil 30% lard with mineral oil Soluble oil
Alloy Steels 10% lard oil with 90% mineral oil Soluble oil 30% lard oil with 70% mineral oil 25% sulphur base oil with 75% mineral oil
Cast Iron Dry Dry Dry or 25% lard oil with 80% mineral oil Dry
Malleable Iron Soluble oil Soluble oil Soluble oil Soluble oil
Copper Soluble oil Soluble oil Soluble oil Soluble oil
Low Carbon and Tool Steels Soluble oil Soluble oil 25-40% lard oil with mineral oil 25% lard oil with 75% mineral oil
 
Types of cutting fluid:
 
  • Straight oils
These oils are non-emulsifiable and very useful in machining operations where they function in undiluted form. Their composition is a base mineral or even petroleum oil. Often they contain polar lubricants like vegetable oils, fats and esters.They may also contain extreme pressure additives including sulphur, chlorine, and phosphorus. To achieve the best lubrication use straight oils however they may have poor cooling characteristics.
 
  • Synthetic fluids
They do not contain mineral oil base or petroleum. Instead, they’re formulated from the alkaline organic and inorganic compounds alongside additives to prevent corrosion. They function well in their diluted form. Of all the varieties of cutting fluids, synthetic fluids offer the best cooling performance.
 
  • Soluble oils
Soluble Oils usually form an emulsion after mixing them with water. The resulting concentrate contains emulsions and a base mineral oil to produce a stable emulsion. They function well in their diluted form and offer a great lubrication in addition to heat transfer performance. They are the least expensive and are the most widely used fluids in the industry.
 
  • Semi-synthetic fluids
These fluids are basically a combination of the soluble oils and synthetic fluids. Besides, the heat transfer performance and cost of the semi-synthetic fluids falls between those of the soluble and synthetic fluids.