Choosing The Right Coolant

What are coolants

Coolants are an important part of the machining/manufacturing processes such as milling, turning and grinding. They are used to improve tool life and surface finish by dissipating heat, helping to remove swarf (chips) and reducing friction in the machining process. This is to ensure you can maximize performance of the machine and its tooling as well as improving the quality of finish in the workpiece. Selecting the right type of coolant to use can be instrumental in maximizing productivity on your machine.

Most manufacturers of coolant offer a range of different fluids, all having their own benefits and drawbacks.

3 of the most popular types of coolant used in lathes, milling machines and grinders are:

• Emulsified oil (soluble oil)
• Semi-synthetic
• synthetic

These products all require additives for increased foam control, corrosion control, pH stability and improved machining.

Soluble Oils

A very popular and common choice usually forming a milky fluid. On average they are 50%+ oil content, with emulsifiers and additives. The high oil content offers great lubricity and corrosion control of the machine and components. Although, oil emulsifiers are a known breeding ground for bacteria and can impede the heat dissipation process.

Semi-Synthetic

A coolant which contains a synthetic (polymer) and oil, an average oil content for a semi-synthetic coolant can contain anywhere between 5% and 35% oil. The heat dissipation process works much faster with a lower oil content than with a soluble oil, which usually leads to improved tool life and finish.

Synthetic

A wide range of ingredients are usually used in synthetic oils; polymers are used to replace some additives and oil found in soluble and semi-synthetic coolant. Due to limited oil content, additives are used to improve corrosion control. Historic issues with corrosion and hard deposits have been improved greatly in modern coolants. There are now formulas which emulsify limited oil to help improve the performance. Synthetic coolants can offer improved tool life, sump life and superior cooling.

Speak to a specialist

Before deciding which coolant would be best for you it is always a good idea to discuss the application with the manufacturer. There are many factors which can play a role in finding the most suitable coolant such as machine type, material machined, tooling and age of the machine, water hardness and operator exposure. Again, your manufacturer should be able to make a recommendation based on the factors listed.

Managing your coolant

A coolant management system is vital to maximize performance of the machine and the machine tooling. Checking the pH, the dilution rates and bacteria levels are all part of the coolant management process. Not all machine shops have a coolant management system in place and in these cases soluble oils can be the most forgiving. If you can manage the dilution rates a semi-synthetic can be a very effective solution. If you do have a full coolant management system in place, then a synthetic coolant should be the most cost effective and efficient option.

Health and Safety

All coolant manufacturers should be able to offer technical data sheets and safety data sheets for all their products manufactured. These will give you more information on the formula, directions of use, disposal and health risks of the chemicals used in the manufacturing process. Some chemicals such as chlorine and sulphur can cause skin irritation and lung disease although many of the newer coolants on the market avoid using these chemicals due to health and safety risks. It is always best to check with your manufacturer as the operator may have a previous skin condition which could be worsened by exposure to certain additives.