Andrew Darley

Senior Technical Support

24 years engineering experience, specializing in milling, turning, grinding & EDM wire erosion.

When searching for Soluble Cutting Fluids there are many facets to take into consideration.

Over time we have been asked all sorts of queries from customers who have varying levels of knowledge and experience. I have summarised below some of the most frequently asked questions that I am asked on a regular basis...

How should you prepare / mix cutting fluids with water?

When mixing a soluble cutting fluid which contains oil and emulsifier (emulsion or semi synthetic) then it is vitally important to always SLOWLY add oil to water and not vice versa. This is due to how the emulsifiers react with water. Adding water to oil can create an “invert emulsion” which will offer poor performance and instability issues such as short sump life and increased risk of corrosion.

Where possible, an automated mixing device such as a Mixtron should be used to ensure accurate and safe mixing of soluble cutting fluids.

Why do cutting fluids have a concentration range e.g 7-10%? & How important is it to control the concentration of my cutting fluid?

Good concentration control is the most important aspect in maintaining soluble cutting fluids in good, healthy condition and will help to maximise tool life, sump life surface finish and minimise the risk of skin irritation, corrosion, foaming and sticky residues. Using a hand refractometer is an easy method for measuring and maintaining good concentration control.

All coolants are formulated to have a minimum and maximum operating range which is determined by the additives in the formulation and the materials and applications they are designed to work with.

What precautions should you take when mixing cutting fluids?

When mixing soluble cutting fluids, care should be taken to avoid contact with skin and eyes, and the use of appropriate PPE should be observed in line with the manufacturer’s instructions. The use of automatic mixing units such as a Mixtron eliminate the possibility of contact with the concentrated product which significantly reduces the risks associated with handling these products.

Why is your cutting fluid staining your metal?

Certain sensitive materials including aluminium, copper and brass are prone to staining due to contact with certain soluble cutting fluids, particularly after prolonged contact. When machining these materials, careful selection of an appropriate coolant such as Cutsol Ultra V7 is required to ensure that it is passivated to prevent staining and the formation of soaps.

When machining these materials, careful selection of an appropriate coolant such as Cutsol Ultra V7 is required to ensure that it is passivated to prevent staining and the formation of soaps.

What causes corrosion from my cutting fluid and how can I control it?

Corrosion can be caused by a multitude of issues relating to soluble cutting fluids. The most common cause is the coolant concentration being too weak, this can be quickly corrected by increasing to a suitable level. Other causes include bacterial infection, low pH and high chloride levels which can build up on old emulsions, particularly in hard water areas. Carrying out regular concentration and bacteria checks can significantly reduce the risk of corrosion along with planned maintenance to fully clean out the coolant sump at least once per year.

What causes cutting fluids to smell and how can I prevent it?

The rotten egg, sulphur or “Monday morning smell” often associated with soluble cutting fluids is caused by bacteria in the fluid. This can be caused by several factors including the wrong type of coolant for the materials/application, poor concentration control, poor housekeeping and heavy tramp oil contamination. Light to moderate bacterial infections can be controlled by use of a suitable biocide such as Cutwel Bactericide and by ensuring that a suitable systems cleaner is used when carrying out full fluid changes such as Cutwel Cutclean SC.

Why are you getting poor cutting tool life from your cutting fluid?

Poor tool life can be caused due to poor coolant flow to the workpiece, low concentration, bacterial infection and the wrong type of coolant for the material and process. Machining hard and exotic alloys will benefit from a high lubricity coolant such as Cutsol Ultra V7, Cutsol Ultra HW, Cutsol Ultra LF or Custol Crystal Cool.

Why are you getting short fluid life?

There are a few factors which can shorten fluid life, including the wrong product type for the make-up water, running at low dilutions or dilutions below those advised by the manufacturer and poor sump cleaning regimes. The use of a system cleaner such as Cutwel Cutclean SC can have a dramatic impact on increasing coolant sump life as it ensures the new coolant is going into a sterile environment and isn’t being immediately compromised by bacteria harbouring in the system.

Can cutting fluids by recycled?

It is possible to filter and recycle soluble cutting fluids using a Freddy Coolant Vacuum. Unless particularly large volumes of waste coolant are being produced (100 000’s litres p/a) then the only viable option currently available is disposal via an authorised waste disposal carrier.

How often should you dispose of your cutting fluid and clean your machine sump?

This is largely dependent upon the type of machine; volume of work and type of materials being machined. However, it is considered good practice to carry out a full machine clean every 12 months. Before cleaning out, it is essential to run a system cleaner such as Cutwel Cutclean SC through the machine for 24-48 hours beforehand in order to kill of bacterial and fungal infections, clean down dirt and slime that may have accumulated and ensure the new charge of coolant is going into a sterile, clean environment.

What causes skin irritation from cutting fluids and how can I minimize or prevent it?

Skin irritation is often caused by dirty, contaminated coolant entering under small skin abrasions. This can be reduced by regularly filtering the fluid using a Freddy Coolant Vacuum which will help to remove contaminants. Another cause can by elevated concentration for prolonged periods. This can be easily rectified by checking coolant concentration at least weekly using a hand refractometer.

Why & how often should you monitor the pH value of your cutting fluid emulsion?

pH is a measure of the acidity or alkalinity of a fluid. Most soluble cutting fluids are designed to be mildly alkaline (8.6~9.7 pH) as this environment is unattractive for bacteria and difficult for them to survive or proliferate in. pH should be checked and recorded on a weekly basis in line with HSE guidelines.

What else should you monitor cutting fluids for?

In order to maximise fluid life, performance and safety, you should check soluble coolants on a weekly basis for; concentration, pH, tramp oil contamination, odour, appearance and bacteria on a weekly basis. If good bacteria control is evidenced then the frequency of bacteria checks can be extended out following a suitable risk assessment.

What effect does tramp oil have on my cutting fluid? How can I manage tramp oil?

Tramp oil (caused by slideway oil, hydraulic oil etc) can have a detrimental impact on soluble cutting fluids. As the oil floats to the surface, it cuts off oxygen entering the fluid which increases the risk of bacterial infection or shortened fluid life. If tramp oil emulsifies into the coolant, this can lead to increased smoking and compromised tool life and surface finish. Tramp oil can be easily removed by use of a CNC MS2 Oil Skimmer or by skimming off with a Freddy Coolant Vacuum.

What causes foaming in my cutting fluid and how can I control it?

Foam in soluble cutting fluids is usually caused by either chemical or mechanical means. Mechanical means can be blocked filters, significant fluid displacement or low fluid levels which cause air entrainment. This will lead to the coolant foaming excessively and can compromise tool life and surface finish. Chemical issues such as running the coolant concentration above what’s recommended by the manufacturer or using the wrong coolant type for the make-up water or machine type can also cause coolant to foam. Sometimes the use of an antifoam agent such as Cutwel Antifoam Ultra can help to control foam until other parameters are checked and resolved. additives and detergency additives to aid good fines flushing and maintain machine cleanliness.

All Cutwel PRO coolant are free from formaldehyde release biocides and chlorinated paraffins ensuring a good HSE profile and keeping waste disposal costs to a minimum.

How do you clean out a machine tool sump properly?

Machine tool sumps should be cleaned out by first adding a system cleaner such as Cutwel Cutclean SC to the existing coolant 24 to 48 hours prior to clean out. This will help to sterilise the system and break down dirt and slime which has built up in the system. The fluid should then be removed using an industrial vacuum such as a Freddy, taking care to skim off any tramp oil from the surface. If the sump is particularly contaminated, then a secondary flush with a solution of 1% cleaner and 1% coolant mix should be circulated for up to 1 hour before being removed and refilling with new coolant per the manufacturers recommended concentration.

How should you store cutting fluids?

Soluble cutting fluids should be stored at temperatures between 5-40deg c. When stored below 5-degree c the emulsifiers in the concentrate can become frost damaged meaning the coolant will not mix. If this occurs, then the product should be disposed of.

Soluble cutting fluids fall under the oil storage regulations, therefore if storing 200 litres of oil or above then this should be bunded on a suitable oil storage bund.

Where can I find government regulations on cutting fluids?

Exposure to metalworking fluids can cause several health risks, for all government regulations surrounding these, please visit: http://www.hse.gov.uk/metalworking/index.htm

Wide range of cutting fluids from general purpose to high performance.

Wide range of machine tool care products including system cleaners, tramp oil skimmers, fluid mixers, refractometers and more

Freddy leads the way in coolant recycling by eliminating coolant disposal costs and drastically reducing machine downtime.