Operating Guidelines

Water-miscible cutting fluids; TROUBLESHOOTING

Regular routine inspections and advanced adjustment of physical, chemical and microbiological indicators of the process emulsions and solutions help improve effectiveness of the cutting fluids, extend their life and reduce their consumption, improve their processing properties.

While circulating cutting fluids in centralized systems, their concentration, pH, total content of microorganisms, foreign oil and scalpings, corrosion resistance, foaming tendency, etc. are monitored.

If cutting fluids are used for machine tools with separate cooling systems, the scope of the monitored indicators is smaller and mainly includes organoleptic ones (appearance, smell, homogeneity). For example, a bluish white colour of the emulsion compared to a milky white colour of the freshly-mixed emulsion indicates low concentration of the cutting fluid in it; white with yellow or brown tint indicates the content of foreign oil in the emulsion; a grey tint suggests inclusion of metal impurities.

Heterogeneity of the emulsion indicates a significant content of foreign oil, and putrid (hydrogen sulphide) odours suggests that the cutting fluid contains bacteria.

Organoleptic indicators of cutting fluids should be inspected daily, and its full analysis in machine tools with separate cooling systems should be performed selectively in 2-3 machines from a group of 15-20 machines weekly.

Cutting fluids in circulating systems should be inspected twice a week.

Regular quality control of cutting fluids in the process is an integral part of measures to extend their service life and is necessary for the timely and efficient adjustment of operational properties of the cutting fluid.

If the quality indicators of the cutting are abnormal, properties of process emulsions or cutting fluid solutions are to be adjusted. Adjustment methods are shown in the table below. In this case, bactericides, detergent-disinfectants and anti-corrosion additive packages should be added directly into the process emulsions or cutting fluid solutions, while the adjustment of properties by means of cutting fluid concentrates should be carried out with disconnected filter cutting fluid circulation systems or in special containers, followed by stirring.




Emulsion circulation system is heavily clogged with chips, especially with fine dust-like ones, slurry sludges, foreign return oil

  • reduction of the emulsion life
  • processing quality deterioration
  • smell, smoke
  • machine contamination
  • skin exposure
  • filtering (filter functionality check)
  • thorough washing of the machine and all its channels, as well as the cooling system pipelines with detergent TEHMOS-2
  • removal surfaced return oil from the cutting fluid;

Emulsion circulation system is clogged with household waste (human factor): cigarette butts, bread, packages, etc.

  • bacteria, fungi and yeast formation
  • increased risk of skin exposure,
  • reduction of the emulsion life
  • occupational training, personnel instruction;
  • inspection
  • thorough flushing of the system

The number of microorganisms is very high, higher than 106, though there is no smell.

  • possible reduction of the emulsion life
  • possible health risks for the personnel affected by pathogenic microorganisms;
  • reduction of the carry-over performance of the cutting fluid
  • check and increase the concentration
  • add a biocide to the system;
  • thorough flushing of the system and emulsion replacement

pH of the process emulsion is very high (over 9.0)

GOST 6243-75, para. 4

  • skin irritation
  • check if the concentration is too high
  • check for the foreign alkaline materials in the emulsion

pH of the process emulsion is very low. Amine cutting fluids: less than 8.6,

cutting fluids without amines: less than 8.0

Recommended range

pH 8.5 – pH 9.3

  • decrease in emulsion stability
  • “sour” odour
  • reduction of the emulsion life
  • rapid growth of bacteria
  • deterioration of anti-corrosion properties
  • check if the concentration if too low; check for foreign acidic materials or increase in the number of microorganisms
  • increase the concentration
  • add an alkalizing additive and a biocide

Deterioration of anticorrosive performance of the process emulsion

GOST 6243-75, para. 2.1

  • tool corrosion
  • equipment corrosion
  • (increased levels of chloride sulphate ions)










  • increase the concentration
  • change the environment conditions (when operating in conditions of high humidity and exposure to condensation)
  • avoid formation of an aggressive environment, gas; use exhaust ventilation
  • check pH
  • bacteria test
  • double-check the type of the cutting fluid (e.g., mineral oil content)
  • add an anti-corrosion additive to the system
  • change the tool storage conditions
  • eliminate accumulated chips from the chip conveyor

Foaming above normal

  • equipment and work area contamination
  • inadequate cooling and lubricating properties of the emulsion due to air suction by the pump
  • decrease in filtration efficiency
  • increased concentration
  • insufficient water hardness
  • bacteria and fungi formation
  • check the quality of water
  • identify and repair a defective air pump
  • change hydrodynamics of the cutting fluid flow in the tank and filtration system
  • increase emulsion level in the system
  • increase water hardness
  • check for emulsion instability (foreign return oil content)
  • add an anti-foam agent to the system;
  • check the emulsion supply pressure

Water hardness is too high

Recommended water hardness

10…20°dH, equivalent to

1.79 ….3.58 mmol/l (1°dH = 0,179 mmol/l or 0.357 millival/l)

Chlorine content should not exceed 150 mg/l

  • deterioration of anti-corrosion properties and settling-out of calcium soaps
  • soften a portion of water required for the preparation of the emulsion by means of an ion exchange process or the addition of sodium carbonate or sodium orthophosphate

Low level of the cutting fluid in the tank

Concentration adjustment

  •  If the cutting fluid level does not reach the MIN (minimum) level, it will cause damage to pumps and processing failures
  • control the level in the tank of the cutting fluid supply unit
  • add the emulsion with a slightly lower concentration, as over time its concentration increases due to emulsion evaporation

Adverse effects on the skin

  • short or prolonged deterioration
  • seek medical advice
  • change a workplace
  • wash with softening detergent
  • apply water-resistant skin cream during work
  • apply a moisturising hand cream after work
  • regular training and briefing of the personnel working with the cutting fluid
  • prevent contamination of the emulsion
  • remove surfaced return oil regularly
  • monitor the total number of microorganisms
  • observe with the general rules of personal hygiene 
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