Editing Cutting fluid (section)

=== Air or other gases (e.g., nitrogen) ===
Ambient air, of course, was the original machining coolant. Compressed air, supplied through pipes and hoses from an [[air compressor]] and discharged from a nozzle aimed at the tool, is sometimes a useful coolant. The force of the decompressing air stream blows chips away, and the decompression itself has a slight degree of cooling action. The net result is that the heat of the machining cut is carried away a bit better than by ambient air alone. Sometimes liquids are added to the air stream to form a mist (mist coolant systems, [[#Aerosols (mists)|described above]]).

[[Liquid nitrogen]], supplied in pressurized steel bottles, is sometimes used in similar fashion. In this case, boiling is enough to provide a powerful refrigerating effect. For years this has been done (in limited applications) by flooding the work zone. Since 2005, this mode of coolant has been applied in a manner comparable to [[#MQL|MQL]] (with through-the-spindle and through-the-tool-tip delivery). This refrigerates the body and tips of the tool to such a degree that it acts as a "thermal sponge", sucking up the heat from the tool–chip interface.<ref name="Z2">{{Citation |last=Zelinski |first=Peter |date=2011-01-28 |title=The 400° difference |journal=Modern Machine Shop |volume=83 |issue=10 |url=http://www.mmsonline.com/articles/the-400-difference }}</ref> This new type of nitrogen cooling is still under patent. Tool life has been increased by a factor of 10 in the milling of tough metals such as [[titanium]] and [[inconel]].<ref name="Z2"/>

Alternatively, using airflow combined with a quick evaporating substance (ex. alcohol, water etc.) can be used as an effective coolant when handling hot pieces that cannot be cooled by alternate methods.