1. Total Lubricants USA Technical Training Series: Metalworking Coolants

2. Coolants Water-containing fluids designed to:
provide lubrication between tool and workpiece
remove heat from surfaces
flush away debris created during machining
Coolants are used in place of cutting oils because:
heat removal is about 2-3 times faster than oil
much thinner in composition which allows faster machining with closer tolerances
produce less misting than similar viscosity oils
typically are easier to dispose of

3. Coolant Use
Coolants are used to perform many different metalworking tasks including:
turning
boring
drilling
sawing
honing
milling
grinding
broaching
gear hobbing, etc.

4. Metalworking Fluid Selection
Selection of a particular MWF depends on the:
type of machine and operation
type of metal and speed of cut
machine lubrication requirements
MWF’s must provide effective rust & corrosion protection for the tool, workpiece, and machine
MWF’s consist of 4 basic types:
straight oils
emulsifiable (“soluble”) oils
synthetic fluids
semi-synthetic fluids

5. Types of Metalworking Fluids

6. Emulsifiable Oils Known in the industry as “Soluble Oils”
Consist of about % oil
Usually formulated with naphthenic oils
Common additives include sulfur, chlorine, & fats
Form oil-in-water emulsions
Provide good tool life, anti-weld properties, and rust & corrosion properties
Typically provide the best lubricating properties

7. Synthetic Coolants Contain large quantities of water but no oil
Form a clear or translucent solution when mixed with water
Have a higher pH than emulsifiable type oils
Provide benefits such as increased workpiece visibility, good wetting properties, stability, tramp oil rejection, and little rancidity
Formulated with rust & corrosion inhibitors, extreme pressure enhancers, biocides, surfactants, anti-foam agents, & more

8. Semi-Synthetic Coolants
Formulated much like a synthetic fluid but contain from 5 to 25% oil
Designed to combine the best features of both emulsifiable oils and synthetic fluids
Offer better lubricity than synthetic fluids and better visibility & tramp oil rejection than emulsifiable oils
Provide a good finish on most non-ferrous metals and recommended where other fluids are not practical

9. Coolant Performance
Successful performance of any coolant depends primarily on proper:
storage of the concentrate (neat coolant);
preparation of coolant dilutions for the initial charge and for daily makeup;
maintenance of coolant dilutions including the use of good housekeeping techniques; and
routine condition monitoring by a laboratory to detect and correct discrepancies before problems arise

10. Proper Storage
Storage methods are important to the success of the finished product
Improper handling can render a coolant useless or may lead to premature solution failure
Coolant concentrate should be stored inside between 50o and 100oF; outside storage should be avoided
Concentrate must be protected from moisture

11. Coolant Make-Up Water Make-up water must be of suitable quality
The pH & water hardness along with chlorides, sulfate, and iron content must be considered
Hard water can split emulsions and form scum
Chlorides can split emulsions and create rust
Sulfates may promote microorganism growth
Hard water discourages foam; soft water provides the best emulsion stability

12. Coolant Dilutions
Coolant should be added at the point of maximum agitation
Coolant mixtures should be prepared using dedicated mixing equipment and containers
To initially charge a system, it is necessary to know the sump capacity of a machine or system

13. Maintenance of Coolant
Coolant maintenance is absolutely essential to ensure consistent quality of manufactured parts
Daily checks are needed since coolant dilutions are constantly changing through carry-off on parts, water evaporation, oil leaks, etc.
Individual operators have the best ability to detect potential problems and maintain coolant solutions by performing simple daily checks

14. Maintenance of Coolant
Daily checks by operators should include:
verifying coolant concentration
noting abnormal conditions such as excess tramp oil, solids, and/or foam, abnormal appearance or odor, etc.
Routine lab testing is performed by Total Lubricants to ensure satisfactory fluid performance
If a problem is detected from lab testing, corrective actions are implemented to ensure uninterrupted service from the coolant
Water vaporization from machine sumps usually makes it necessary to add makeup coolant at a reduced concentration level

15. Coolant Concentration
Concentration is the single most important factor to coolant success:
concentration must be maintained as consistently as possible within an established range
rich concentrations may cause an increase in skin irritation, produce excessive foaming, reduce the coolant’s ability to remove heat, & increase costs
lean concentrations can destroy tool life, create rust and corrosion problems, promote growth of microorganisms, and lead to rapid fluid failure

16. Concentration by Refractometer
A fast and easy method for checking coolant concentration is with a handheld refractometer.
A refractometer is an optical instrument that reads the amount of total solids by passing light through a sample of coolant.
Synthetic coolants produce the sharpest line on a refractometer; soluble oils are often difficult to read accurately
Tramp oil or chemical contaminants may cause inaccurate readings

17. Routine Lab Testing Coolant condition monitoring tests include:
concentration
total alkalinity
total oil content (“soluble”/semi-synthetic) pH
microbe activity (aerobic/anaerobic bacteria & fungi)
solids
tramp oil
cation levels (Ca, Mg, Na, Fe, Al)
conductivity
rust prevention properties

18. pH pH expresses the hydrogen ion concentration in a solution
pH scale ranges from 0-14; is acid; 7.0 is neutral; and, is alkaline
pH is measured with pH paper or electronic meter
A high pH (8.5+) promotes good protection from corrosion and microorganisms
A low pH is best for non-ferrous metals and is kinder to an operator’s skin.

19. Control of Microorganisms
Coolants provide an excellent environment for the growth and reproduction of microorganisms
Common microorganisms consist of bacteria and fungi (yeast and molds)
Microorganisms digest helpful ingredients and produce foul odors
Microorganism content is determined by growing cultures from coolant samples
Biocides may be added to fluid to combat growth

20. Foam
Some foam is good since it cleans machine surfaces and promotes good wetting properties
Excessive foam, however, is a safety hazard and may cause pump cavitation
Foaming is dependent on coolant concentration, water hardness, type of coolant, agitation, and severity of the operation
Foam may be effectively controlled with anti-foam agents

21. Tramp Oil
A layer which floats on the surface & consists of split-out oil, carry-over oil, and/or process oils
Tramp oil causes incorrect refractometer readings, severe loading of grinding wheels, and a reduction in heat removal capacity and wetting ability
Failure to control tramp oil often leads to an increase in the growth of microorganisms
Effective control can usually be obtained by using oil skimmers and felt-covered wipers

22. Solid Contaminants
Solids are formed during the machining process and consist of fines, shavings, and dirt
Solids which are not effectively removed can scratch surfaces and interfere with close tolerances
Solids provide additional breeding ground for microorganisms and promote operator dermatitis
Most solid contaminants can be reduced or eliminated through the use of magnetic skimmers, filters, and chip separator devices

23. Operator Procedures
Prior to the beginning of the shift & throughout the work day:
observe the holding tank to detect any significant changes in tramp oil levels, dirt, or fungal growth (slime)
slime-type growth on walls should be reported as soon as observed so that an anti-fungal treatment can be added (line clogging can quickly become a problem)
“dirty” sumps should be changed out as soon as production & maintenance schedules permit
operators will obtain a “feel” for the general operating condition of their machine through daily inspections

24. Dermatitis Dermatitis is an irritation or inflammation to the skin
Coolants contain surfactants and wetting agents (soaps) which tend to dry skin
Alkaline cleaners, degreasers, solvents, and abrasive cleaners further irritate the skin
Common industrial irritants include kerosene, chlorinated solvents, acidic solutions, and metals including chromates, zinc, cadmium, & mercury

25. Dermatitis
Factors external to the work environment which may cause dermatitis include:
poison ivy, poison oak, ragweed, and sumac
white pine, Frazier fir, & teak trees
lemons, oranges, & onions
penicillin, sulfa-drugs, & anti-histamines
dyes, bleaches, deodorants, & nail polishes
wool, silk, nylon, leather, & fur
detergents, polishes, & waxes

26. Dermatitis Synthetic coolants tend to dry out skin the most
Dermatitis, by definition, is not caused by bacteria although bacteria may aggravate an existing case of dermatitis
Factors such as age, type of skin, previous exposure, & duration of contact determine an individuals’ susceptibility level to dermatitis
Proper fluid maintenance and operator hygiene are key factors in preventing or reducing dermatitis