1. Main Metalworking Processes

1.1. Turning

• Characteristics: A cutting tool removes material while the workpiece rotates on a lathe.
• Purpose: Produce external and internal cylindrical surfaces, flats, threads, and special profiles.
• Applied technologies: External turning, boring, threading, profile turning.
• Products: Shafts, bushings, bolts, threaded rods, round-shaped parts.
• Lubricant requirements: Reduce friction, provide rapid cooling, flush chips, prevent tool wear.

1.2. Milling

• Characteristics: A multi-tooth milling cutter rotates while the workpiece is clamped.
• Purpose: Machine flat surfaces, grooves, steps, gears, and 3D contoured surfaces.
• Applied technologies: Face milling, end milling, gear milling, CNC milling.
• Products: Molds, machine bases, complex parts.
• Lubricant requirements: Reduce friction, extend tool life, limit heat generation.

1.3. Drilling – Reaming – Boring – Tapping

• Drilling: Produce rough holes.
• Reaming: Enlarge and finish holes to precise size and surface quality.
• Boring: Re-machine existing holes to high dimensional accuracy.
• Tapping: Create internal threads.
• Products: Assembly holes, threaded fasteners, locating holes.
• Lubricant requirements: Provide good lubrication, reduce cutting friction, flush chips from holes.

1.4. Grinding

• Characteristics: High-speed grinding wheels remove very thin layers of material.
• Purpose: Achieve high dimensional accuracy and fine surface finish (Ra ≤ 0.4 µm).
• Types: Cylindrical, surface, centerless, thread grinding, finishing.
• Products: Bushings, spindles, precision components, molds.
• Lubricant requirements: Low viscosity (2–10 cSt), fast heat removal, low volatility, anti-foam properties.

1.5. Shaping and Slotting

• Characteristics: A single-point tool reciprocates across the workpiece.
• Purpose: Produce flat surfaces, grooves, steps.
• Products: Long flats, keyways, large parts difficult to mill.
• Lubricant requirements: Moderate lubrication primarily to reduce surface friction.

1.6. Broaching

• Characteristics: A broach with progressively larger teeth cuts in a single stroke.
• Purpose: Machine holes, keyways, and precise profiles.
• Products: Square holes, splines, gears.
• Lubricant requirements: Medium-viscosity oils with EP additives to prevent sticking/seizure.

1.7. Stamping and Rolling

• Stamping: Dies and presses cut, bend, or deep-draw sheet metal.
• Rolling: Rolls compress the workpiece to reduce thickness or form shapes.
• Products: Housings, metal lids, rolled steel sheets, cold-formed parts.
• Lubricant requirements: EP additives and tackifiers; sometimes grease, graphite, or molybdenum-based lubricants.

1.8. High-Speed Cutting (HSC)

• Characteristics: Extremely high cutting speeds generate heat rapidly and accelerate tool wear.
• Products: High-precision parts, fine-finish mold components.
• Lubricant requirements: Highly refined base oils, low ash, high flash point, oxidation inhibitors.

1.9. Electrical Discharge Machining (EDM)

• Characteristics: Sparks or a wire electrode remove material by localized melting.
• Purpose: Machine complex shapes and very hard materials.
• Products: Stamping dies, plastic molds, precision parts.
• Lubricant requirements: Dielectric EDM oils, low viscosity (2–3 cSt at 40 °C), clear, low smoke.

1.10. Polishing – Honing – Lapping

• Characteristics: Fine finishing processes requiring extremely smooth surfaces.
• Purpose: Remove minor dimensional errors and produce mirror-like finishes.
• Products: Bearings, cylinders, optical components, precision molds.
• Lubricant requirements: Low viscosity, high purity, low residue, light anti-wear additives.

1.11. Welding

• Characteristics: Heat, pressure, or both are used to join metals.
• Methods: Arc, TIG, MIG, resistance, laser welding.
• Products: Steel structures, frames, pipelines.
• Note: Cutting fluids are not used directly; surfaces should be treated to prevent oxidation.

1.12. Heat Treatment and Surface Treatment

• Heat treatment: Quenching, tempering, normalizing, annealing to adjust mechanical properties (hardness, ductility).
• Surface treatment: Plating, carburizing, nitriding, shot blasting to enhance hardness, wear resistance, and corrosion protection.
• Products: Camshafts, gears, cutting tools, molds.

2. Lubricant Requirements in Metalworking

2.1. Main functions

• Cooling
• Lubrication
• Cleaning
• Protection

2.2. Required technical properties

• Appropriate viscosity
• Anti-wear & EP performance: Sulfur-, phosphorus-, and chlorine-containing additives.
• Chemical stability: Oxidation resistance; biostability for water-miscible fluids.
• Safety: Low smoke, non-irritating to skin, high flash point.
• Environmental compatibility: Easy oil–water separation and waste handling.

2.3. Types of cutting fluids

• Mineral oils
• Synthetic fluids
• Semi-synthetic fluids
• Soluble (emulsifiable) oils

3. Current Trends

• Water-miscible fluids: Fast cooling and cost efficiency; require microbial control.

• Straight oils: High lubricity; suitable for reaming, tapping, and heavy-duty forming.

• MQL (Minimum Quantity Lubrication): Uses micro-quantities of aerosolized oil, saving consumption and reducing environmental impact.