Page 59 - CITS - Fitter - Trade Theory

FITTER - CITS

Definition of coolants: Coolants (Cutting fluids) play an important role in reducing the wear of cutting tools.
Coolants (Cutting fluids) are essential in most metal cutting operations. During a machining process, considerable
heat and friction are created by the plastic deformation of metal occurring in the shear zone when the chip slides
along the chip tool interface. This heat and friction cause the metal to adhere to the cutting edge of the tool, and
the tool may break down. The result is poor finish and inaccurate work.
Types of coolants
1 Water-based coolants
• Soluble Oils: Soluble oils are water-based coolants that contain emulsified mineral or synthetic oils, along
with additives such as corrosion inhibitors, lubricants, and biocides. They offer good lubrication and cooling
properties and are suitable for a wide range of machining operations, including drilling, milling, and grinding.

• Synthetic Coolants: Synthetic coolants are water-based fluids formulated from synthetic chemicals, such
as polyalphaolefins (PAO) or polyglycols. They offer excellent cooling and lubricating properties, high
stability, and resistance to bacterial growth. Synthetic coolants are suitable for high-speed machining,
aluminum machining, and operations requiring tight tolerances.
2 Oil-based coolants
• Straight Oils: Straight oils, also known as neat oils, are mineral or synthetic oils used without dilution. They
offer excellent lubrication and cooling properties and are suitable for heavy-duty machining operations,
such as broaching, threading, and gear cutting. Straight oils provide good surface finish and corrosion
protection but may require additional cleaning due to their high viscosity.
• Semi-synthetic Coolants: Semi-synthetic coolants are oil-based fluids blended with water to create an
emulsion. They combine the lubricating properties of oil with the cooling and flushing properties of water.
Semi-synthetic coolants offer improved stability and performance compared to soluble oils and are suitable
for a wide range of machining operations.
3 Synthetic coolants
• Polyalphaolefins (PAOs): PAOs are synthetic hydrocarbon-based fluids known for their high thermal
stability, oxidation resistance, and lubricating properties. They are suitable for high-temperature machining
operations, such as aerospace machining and hard metal machining.

• Polyalkylene Glycols (PAGs): PAGs are synthetic fluids with excellent lubricating and cooling properties.
They offer high thermal stability, low volatility, and resistance to microbial growth. PAGs are suitable for
machining operations involving high-speed steel, stainless steel, and non-ferrous metals.
4 Vegetable-based coolants
• Vegetable Oils: Vegetable-based coolants are derived from natural oils, such as soybean oil, rapeseed
oil, or coconut oil. They are biodegradable, environmentally friendly, and offer good lubrication and cooling
properties. Vegetable-based coolants are suitable for applications where environmental concerns are
important, such as food processing and agricultural machinery.
5 Air-based coolants:
• Air or mist coolants: Air-based coolants, also known as air or mist cooling systems, use compressed air
to create a fine mist of coolant that is directed onto the cutting tool and workpiece. Air-based coolants offer
minimal fluid consumption, reduced environmental impact, and improved operator safety. They are suitable
for high-speed machining operations and applications where fluid contact is limited.
Application of coolants:
- Cools the tool and the work piece

- Lubricates the chip / tool interface and reduces the tool wear due to friction
- Prevents chip welding - Improves the surface finish of the work piece
- Flushes away the chips
- Prevents corrosion of the work and the machine

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CITS : CG & M - Fitter - Lesson 8