Cutting Fluids

High-pressure coolant (HPC) aids in chip evacuation and helps keep the cutting tool cool and well-lubricated. It is a must for all gundrilling operations.

Three types of coolant (cutting fluid) are used in machining operations — straight or neat oil, synthetics and semi-synthetics, and water-soluble or emulsion-style fluids.

As a rule, straight oil provides the best tool life, provided it contains sulfur and/or chlorine. Sulfur’s anti-weld properties help prevent built-up edge (BUE) on the cutting tool, while chlorine acts as a lubricant, further enhancing chip evacuation.

Water-soluble cutting fluids contain up to 50% mineral oil, with the balance comprised of water, chemicals, and extreme-pressure (EP) compounds for lubricity. Water-solubles provide more effective cooling and have environmental advantages over oil, although its use can result in shorter tool life.

Similarly, synthetics and semi-synthetics are a chemical solution that contain little to no mineral oil. These fluids require concentration levels of at least 8%, with 10% ideal. However, synthetic cutting fluids can reduce tool life significantly compared to straight oil.

Recommended Coolant Pressures