Which option is a common cutting fluid used for cutting metals?

A common cutting fluid used for cutting metals indeed encompasses a variety of substances that can be effective in reducing heat and friction during the machining process, improving the life of cutting tools, and enhancing surface finish.

Water mixed with soda or borax serves as an effective coolant and lubricant in certain applications, particularly when it comes to soft metals. Light mineral oil is another cutting fluid that provides excellent lubrication properties and is suitable for various machining operations, especially for non-ferrous metals. Soluble oil, which is an oil that can be diluted with water, combines the benefits of oil and coolant, providing both lubrication and cooling. By mixing it with water, it can decrease tool wear significantly while also dissipating heat during cutting.

Thus, the inclusion of all of these options indicates that they are all valid choices for cutting fluids in metal machining processes, reflecting the broad application of various cutting fluids across different machining scenarios.