Why Is Cutting Fluid Concentration So Important?

Water-soluble cutting oils must be diluted before use. The ideal concentration varies depending on workpiece material and cutting load.

Low concentration can result in:

■ Insufficient rust prevention

■ Faster tool wear

■ Bacterial growth in stagnant tanks

■ Foul smell (due to coolant degradation)

Excessively high concentration may cause:

■ Increased oil usage and cost

■ Residue buildup on parts

■ Smoke generation affecting operator safety

Real Case: Severe Rust Due to Low Concentration

A metal machining factory reported a surge in customer complaints due to severely rusted workpieces, leading to high return rates.After inspection, it was found that the coolant concentration had dropped to 2.5%, well below the recommended 6%.Root cause: No regular monitoring or refilling,coolant evaporation over time,coolant sitting idle and allowing bacterial growth and odor

Solution: 1. Weekly testing with a refractometer 2.Monthly coolant replacement 3.Use of an oil-water separator to prevent contamination 4.Maintaining target concentration at 7–9%, with pH between 8.5–9.5.

Result: Quality stabilized within 3 weeks, and rust complaints dropped by 80%.

How to Measure & Adjust Cutting Fluid Concentration

Common Measurement Methods:

■ Refractometer: Fast and accurate method used on-site

■ pH Test Strips: Track coolant health and detect potential bacterial growth

■ Watch out for false readings: Contamination by slideway oil or hydraulic oil may affect results. Always combine testing with visual inspection.

Adjustment Guidelines:

■ Too concentrated? → Gradually dilute with water while stirring thoroughly

■ Too weak? → Add concentrated oil. Avoid adding too much at once to prevent separation

3 Daily Tips to Extend Coolant Life

1. Regular concentration & pH checks:Test coolant 2–3 times per week and record trends. This helps you make timely refills or corrections.

2. Circulate coolant regularly:Idle tanks allow bacteria to grow. Run the machine for 30 minutes weekly to circulate fluid and prevent odor.

3. Use filtration & separation equipment:Install oil skimmers, filters, or magnetic separators to remove debris, tramp oil, and fine particles. This prevents clogging and helps extend coolant lifespan.

Proper cutting fluid concentration management isn't just about performance—it's about cost control, product quality, and operator safety.

By maintaining the right concentration and following daily practices, you can:

■ Improve tool life

■ Reduce rust and waste

■ Keep your shop environment clean and odor-free

Need help selecting the right coolant or managing your cutting fluid system? Our team at Hai Lu Jya He is here to assist with full-service support and expert advice. Feel free to contact us today for a customized solution!