Metalworking Fluid Selection

(See Also "Selecting the Perfect Metalworking Fluid - by Jerry Byers [MFM])

Attached below is a protocol that serves the purpose of providing a base point of reason and logic for the decision-making process regarding testing and replacement of metalworking fluids in a manufacturing facility.  Most individuals with this responsibility are besieged by workers and supervisors complaining about the coolant and wanting to replace it with the "Super Euro-Something" from the salesman who gave him the complicated pocket weapon.

Everybody has a solution, nobody has any facts, you have limited means of acquiring any facts, and:



Carve it in stone.  While only large manufacturing facilities will have laboratory testing capability, there are outside labs and magazines such as this one to help fill in.  But don't underestimate the need for lab analysis.  If you don't believe anything else you ever read in this EMag, you better believe this: You CANNOT intelligently select the best metalworking fluid by "trying it out on a machine".  Forget about it.  There are far too many variables between fluids, machines, and operations and you will be wasting time and money.  You are not likely to learn anything, and anything you do learn will apply to that machine alone.  Worse, you have established precedence on a procedure that doesn't work.

The Coolant salesman (see picture) will want you to do it this way.  He will offer to watch the coolant during the test period, which guarantees the results will be screwed up from the beginning.  First, he will clean out your machine with dental tools. Second, he will "keep an eye on it" by strapping a refractometer to his skull and smuggling miniature electronic monitoring equipment into your plant. Third, he will pay-off the machinist with a daily supply of sales aids so that he will smile and appear happy while frequently bragging about the product.  Fourth, he will "drug" your machine with enough biocides, herbicides, and pesticides to sterilize both the machine and the operator.


Even if you decide that I might be exaggerating (and I am), and you're just a field test kinda guy, you will have established a destiny of repetition, where you are constantly asked to just..."try another one out on this other machine". There is always the shop Einstein that goes around saying "Just cause it werks in the lab don't mean it'll werk out here". Well Albert, odds are that as a matter of fact, it will.


It our opinion, field tests are necessary - but only after lab testing in the hierarchy of a proper protocol.

In upcoming issues, we will detail some low and medium budget lab testing that anybody can do to help bring sense to the nonsense of the metalworking fluid selection process.

If, on the other hand, the budget is no object, your boss has a pure science approach, and you have some serious lab time to kill, see the Literature section of this publication for some hard core options. If this is you, please write to us and tell us what planet you work on.

Model Metalworking Fluid Recommendation, Testing, and Selection Protocol



The purpose of this policy is to:

1. ensure the integrity of the MWF selection and testing process;
2. conserve resources required for testing and approval;
3. protect the health and safety of employees and the environment;
4. add stability to manufacturing and purchasing practices;
5. incorporate scientific procedures in the decision-making process;
6. make the best decision possible.


No new MWF will be "Approved for General Use" until an existing MWF is removed from service and from the Approved Chemical Database.

Recommendation Procedure

1. Recommendation for Testing from a Department Manager qualified as a "Responsible Party" (see below).
2. EHS approval for health, safety, and environmental use and disposal
3. Price quotation in writing
4. Lab Testing.
5. Shop testing on at least 3 (dissimilar) machines
6. Evaluation of tested MWF by each Responsible Party

Responsible Parties

To qualify for testing, a request must originate from one of three Department Managers:

1. Plant Manager / Manager of Manufacturing Engineering
2. Environmental or EHS Manager
3. Manager of Purchasing
Criteria for Testing Recommendation

The requirement criteria that each manager uses should be individually associated with the expertise of the Manager.

Example recommended criteria:

1. Plant Manager / Manager of Manufacturing Engineering

There is substantial evidence that the recommended MWF may provide a significant improvement in performance [tool life, part quality, machinability, machine life, etc].

2. EHS Manager

There is substantial evidence that the recommended MWF is significantly safer for employees and/or the environment [misting, bacterial resistance, disposability, etc.].

3. Manager of Purchasing

There is substantial evidence that the recommended MWF will provide an equivalent performance and safety at a significantly reduced cost [MWF life cycle, disposal cost, recommended concentrations, purchase cost, etc.].

Substantial Evidence

Department Managers should understand that the Substantial Evidence criteria is intended to limit testing to products for which there is a quantity of tangible, discernible evidence which demonstrates the potential of the MWF to produce the required "significant" results.  Examples of such substantial evidence include:

1. Published test results.
2. Analytical and chemical data.
3. Material Safety Data Sheets.
4. Papers published in recognized trade journals.
5. Written quotations.
Manufacturer’s brochures and salesperson’s representations alone are generally insufficient.

Significant Results

Department Managers should understand that the Significant Results criteria is intended to limit testing to products for which there is substantial evidence available to demonstrate the potential of the MWF to produce results that are consequential, material, or significant in nature. Examples of such results include:

1. Cost savings of 5%.
2. 10% improvement in 4-ball lubricity test results.
3. A MWF with an NPFA health category improvement.
4. A MWF that addresses an existing and identified issue [performance, EHS, or other].

Laboratory Testing

Laboratory testing should be required to distinguish the performance differences between metalworking fluids, particularly when an issue with the exsiting MWF has been indentified.  Manufacturing employees are constantly tempted to test a new product on a machine.  Quantification and qualification of performance differences in metalworking fluids cannot normally be accomplished on machines alone, as discernable by machine operators.  There are simply too many variables in operation and environment. Controlled laboratory testing and respect for the scientific method can save tens of thousands of dollars. Laboratory testing can include many things, such as:

1. Corrosion Inhibition
2. Elastomer Capability
3. Surface Coating Compatibility
4. Plexiglas Compatibility
5. Oil Rejection
6. Lubricity
7. Foaming Resistance
8. Heat Transfer Capacity
9. Bacterial Growth Inhibition
10. Misting
11. Employee Sensitivity Testing

Shop Testing

After successful laboratory testing, a proposed metalworking fluid should be tested in the manufacturing environment. This is necessary to qualify the performance of the metalworking fluid under application conditions.

Final Approval

Approval to add the new MWF to the Approved Chemical Database by all Responsible Parties: [EHS, Manufacturing, and Purchasing] and agreement as the the MWF to be removed from the Approved Chemical Database. 


The above article was recently reviewed by Jerry Byers, of Milacron who had this to say: Hello John, I had read the portion of your website on MWF Selection. You make some excellent points in that article. Oddly enough, I wrote an article on this same topic which is appearing in the October issue of TLT. The one area where we might disagree on this subject is in your section on “Criteria for Recommendation.” You state that the EHS Manager must ensure that “There is substantial evidence that the recommended MWF is significantly safer for employees and/or the environment.” This is an excellent idea, but there is no easy way to ensure this since different companies use different internal rules for the wording of the MSDS and HMIS ratings. I discuss this in my article in the October issue. Just because company A gives their product a “1” on health ratings and company B gives theirs a “0” does not mean the B is safer. Company B may not have any toxic data on their product, operating on “faith” in the safety of their product. Neither can one select products based upon the number of “hazardous ingredients” listed. Again, that would assume all companies use the same standards for what to list. They don’t.

Everything Jerry says is right, (of course) but we note that the criteria above is not limited to MSDS and HMIS ratings. That was listed as an example, and as Jerry points out, not a very good one.  It is always possible that something will show-up in these documents, but there are better metrics available by which the criteria can be met.  For example, if the use of a metalworking fluid is suspected of causing health issues such as dermatitis, an alternative fluid can be considered and sensitivity to the proposed product can be tested.  Also, resistance to microbial growth can be tested in existing and proposed products.  As another example, the misting of fluids can be tested in shops where fluid mist is determined to be an issue, and the results of the test can be a basis for believing a substantial improvement can be made.