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In addition to fully understanding the operating conditions, be sure to question all assumptions about MWFs. Many of them are the tribological equivalent of old story tales.
Metalworking fluids (MWFs) are a key production aid in the manufacture of metal parts, from seemingly simple items such as coins and wire to complex objects such as medical devices and engines for aerospace applications. These fluids are used because it is more cost effective to run most operations with a fluid than without The benefits include more high quality finished parts by the end of the shift with lower tool wear, reduced grinding wheel usage and less machine downtime.
MWFs help maintain a constant temperature for the metal part, the tool and the machine-improving dimensional stability of the parts produced. Temperature control is achieved through (1.) lubricants that reduce heat generation and (2.) the cooling action of the fluid that removes heat. The fluid is also used to carry metal particles (chips) away from the cutting zone to an area where they are separated and collected.
The benefit for tool life is shown in Figure 1, a graph of tool wear vs. machining time for a turning operation where 390 aluminum is being machined with polycrystalline diamond tooling under two conditions: either dry or with a semisynthetic MWF being applied. Notice that tool wear is greatly reduced and the time between tool changes is dramatically extended when the fluid is applied.
An additional benefit is that MWFs keep metal fumes and dust out of the air. One study published in Applied Occupational Environmental Hygiene showed that in many situations where water-based fluids were in use, total paniculate in the air was less than when cutting metal dry.(1) STLE member Lloyd Lazarus of Honeywell FM&T, LLC, in Kansas City, Mo., describes how one plant handles metal dust concerns: "(Stainless steels are) high in nickel and chrome content. When machined, a microscopic amount of dust is generated at the chip-workpiece interface. These microscopic particles are breathable and present a health hazard (based on the ACGIH TLV). When we use cutting tools that are designed to run dry (to obtain better tool life) in an enclosed machine tool, we use the MWF to wash the dust from the part,...