Editing Cutting fluid (section)

==Function==
{{Unreferenced section|date=May 2023}}

=== Cooling ===
Metal cutting  generates [[heat]] due to friction and energy lost deforming the material.<ref>{{Cite journal |last=Abukhshim |first=N. A. |last2=Mativenga |first2=P. T. |last3=Sheikh |first3=M. A. |date=2006-06-01 |title=Heat generation and temperature prediction in metal cutting: A review and implications for high speed machining |url=https://www.sciencedirect.com/science/article/abs/pii/S089069550500180X |journal=International Journal of Machine Tools and Manufacture |volume=46 |issue=7 |pages=782–800 |doi=10.1016/j.ijmachtools.2005.07.024 |issn=0890-6955|url-access=subscription }}</ref> The surrounding air has low [[thermal conductivity]] (conducts heat poorly) meaning it is a poor coolant.<ref>{{cite journal |last1=Tai |first1=Bruce L. |last2=Dasch |first2=Jean M. |last3=Shih |first3=Albert J. |title=Evaluation and comparison of lubricant properties in minimum quantity lubrication machining |journal=Machining Science and Technology |date=October 2011 |volume=15 |issue=4 |pages=376–391 |doi=10.1080/10910344.2011.620910 }}</ref> Ambient air cooling is sometimes adequate for light cuts and low duty cycles typical of [[maintenance, repair and operations]] (MRO) or hobbyist work. Production work requires heavy cutting over long time periods and typically produces more heat than air cooling can remove. Rather than pausing production while the tool cools, using liquid coolant removes significantly more heat more rapidly, and can also speed cutting and reduce friction and tool wear.

However, it is not just the tool which heats up but also the work surface. Excessive temperature in the tool or work surface can ruin the [[Tempering (metallurgy)|temper]] of both, soften either to the point of uselessness or failure, burn adjacent material, create unwanted [[thermal expansion]] or lead to unwanted chemical reactions such as [[oxidation]].

Regulating the heat created during machining processes is necessary to extend tool life, prevent the alteration of the workpieces heat treatment, and prevent warping of the piece.<ref>{{Citation |last=Abdelbary |first=Ahmed |title=Introduction to engineering tribology |date=2023 |work=Principles of Engineering Tribology |pages=1–32 |url=https://www.sciencedirect.com/topics/materials-science/cutting-fluid#:~:text=Main%20purposes%20of%20cutting%20fluids,and%20reduces%20cutting%20tool%20wear. |access-date=2025-04-14 |publisher=Elsevier |language=en |doi=10.1016/B978-0-323-99115-5.00013-X |isbn=978-0-323-99115-5 |last2=Chang |first2=Li|url-access=subscription }}</ref> The use of cutting fluids allows machinists to cut faster than they would be capable of if relying on surrounding air to cool the workpiece. 

=== Lubrication ===
Besides cooling, cutting fluids also aid the cutting process by lubricating the interface between the tool's cutting edge and the chip. By preventing friction at this interface, some of the heat generation is prevented. This lubrication also helps prevent the chips from being welded onto the tool, which would interfere with subsequent cutting.

=== Rehbinder Effect ===
The [[Rehbinder effect|Rehbinder Effect]] is the reduction in strength of a materiel when a [[surfactant]], available in cutting fluids, is applied.<ref name="Chaudhari Rehbinder effect in ultraprecision">{{cite journal |last1=Chaudhari |first1=Akshay |last2=Soh |first2=Zhi Yuan |last3=Wang |first3=Hao |last4=Kumar |first4=A. Senthil |title=Rehbinder effect in ultraprecision machining of ductile materials |journal=International Journal of Machine Tools and Manufacture |date=October 2018 |volume=133 |pages=47–60 |doi=10.1016/j.ijmachtools.2018.05.009 }}</ref> Cutting fluid coats the cutting surface and reduces its surface energy, effectively weakening the material.<ref name="Chaudhari Rehbinder effect in ultraprecision"/> This decreases the force required to make cuts, the wear on tools, and the time required for machining processes.<ref name="Chaudhari Rehbinder effect in ultraprecision"/> The Rehbinder Effect is complicated, relying on the chemical properties and structures of both the cutting fluid and working material, and is therefore difficult for machinists to factor into the planning of machining processes. Experienced machinists may utilize "rules of thumb" or trial and error methods if they consider the effect at all. 

=== Extreme Pressure Additives ===
Extreme pressure additives in cutting fluids create a barrier between the cutting tool and working material.<ref name="Canter Trends in extreme pressure additives">{{cite journal |last1=Canter |first1=Neil |title=Special Report: Trends in extreme pressure additives |journal=Tribology & Lubrication Technology |volume=63 |issue=9 |date=September 2007 |pages=10–18 |id={{INIST|19088019}} {{ProQuest|226959889}} |url=https://www.stle.org/images/pdf/STLE_ORG/BOK/OM_OA/Lubrication_Fundamentals/Trends%20in%20Extreme%20Pressure%20Additives_tlt%20article_Sept07.pdf }}</ref> This barrier prevents contact between the two. If the cutting tool and working material were to make contact, particles from the working material could be welded to the cutting tool.<ref name="Canter Trends in extreme pressure additives"/> these added particles would decrease the accuracy of the tool and its cuts, increase the friction in cutting, and lower the quality of the surface finish.