Reading Assignment
- 21.8 Cutting Fluids
- Haas Video Series
Recommended Reading
Outline
Functions
Cool workpiece and tool
- Temperature is an important factor in tool life
- Influences surface integrity
Lubrication
- Reduces power requirements
- Increases production rates
Corrosion Protection
Inhibit bacterial growth
Chip removal
Inhibit bacterial growth
Chip removal
Oil Vs. Water
Main Advantages
Oil – Lubricity
Water – Cooling Capacity
Oil – Lubricity
Water – Cooling Capacity
- Water is capable of dissipating heat 2.5 times faster than oil.
Wetting
Surface reaction can be:
- Hydrophobic
- Hydrophilic
Contact Angle
Should a cutting fluid’s reaction with the surface be hydrophobic or hydrophilic?
Types of Cutting Fluids
Inactive Cutting Oils
Mineral Oils
- Straight Mineral Oils
- Compounded Cutting Oils
- Blended with additives such as animal and vegetable oils. Increases wetting ability. Alows fluid to penetrate too/chip interace.
- FattyMineral Oils
- Improve surface finish in machining steel, brass, copper, and aluminum
Active Cutting Oils
- Cause a film to develop on tool surface and provide anti-weld properties.
- Contain
- Sulfur
- Chlorine
- Phosphorous
Emulsified Oils (Soluble Oils)
- Oil droplets suspended in water by blending the oil with emulsifying agent.
- Advantages:
- Greater heat reduction, higher cutting speeds
- Potentially cleaner working conditions
- More economical (diluted with water)
- Better operator acceptance (cleaner, cooler parts)
- Improved health and safety benefits
- Not a fire hazard
- Misting and fogging are reduced
Chemical Fluids
Contain no petroleum oil
True-solution Chemical fluids contain no wetting agents, usually clear
Surface-active chemical fluids have wetting agents.
True-solution Chemical fluids contain no wetting agents, usually clear
Surface-active chemical fluids have wetting agents.
Semichemical Fluids
Contain mineral oils
Advantages of Chemical and Semichemical Fluids
- Rapid heat dissipation
- High degree of cleanliness
- Light residual films are easy to remove
- Ease of mixing, little agitation needed
Disadvantages
- Lack of lubricity
- High detergency, irritates hands
- Tend to foam
- Disposal problems
Gaseous Fluids
- Air
- Compressed Air
- Argon, helium, nitrogen have been used, but are expensive.
Pastes and Gels
- Waxes, soap-like lubricants, graphite compounds
- Used where lubrication is much more important than heat removal.
- Tapping
- Drilling
- Used when working against gravity
Factors in Cutting Fluid Selection
- Machining time per part
- Number of rejects from unacceptable surface finish
- Machine downtime due to tool changes and maintenance
- Cutting fluid consumption per part
- Cutting fluid batch life
- Cutting fluid disposal or recycling costs
- Compatibility (workpiece and tool)
Application of Cutting Fluid
- Manual
- Flood
- Mist
- High pressure – through tool
Maintenance Considerations
Clarification/Separation Methods
- Tramp oil skimmers
- Settling (Weirs)
- Centrifuge
- Magnetic Separators
Storage of Concentrate
Water Quality
- Hardness/Softness
Rancidity Control
Bacteria found in fluids
- Aerobic
- Anaerobic
Fungus
Physical Tests
- Concentration (refractometer)
- Viscosity
- Flash Point
- Stability
- Emulsion Stability
- Residue
- Foaming
Chemical Tests
- pH
- Corrosion
Microbiological Tests
Health and Safety
Types of Risk
- Oral Toxicity
- Inhalation Toxicity
- Dermal Toxicity
- Skin Irritation
- Eye Irritation
Rule of thumb: Minimize contact with workers!
Additional Resources
Curran, K. and Blohowiak, C. Cutting Fluid Types and Uses Wisc-Online [http://www.wisc-online.com/objects/MTL5302/MLT5302.htm]
Cutting Fluid Brands
Trim (Master Chemical) E206 is good general purpose cutting fluid
Primrose (Extreme Pressure Lubricant)
