LATHE OPERATIONS - OD1645 - LESSON 1/TASK 1
characteristics. Two mineral oils, kerosene and turpentine, are often used
alone for machining aluminum and magnesium. Paraffin oil is used, alone or
with lard oil, for machining copper and brass.
(c) Mineral-Lard Cutting Mixture. Various mixtures of mineral oils and
lard oil are used to make cutting oils which combine the good points of both
ingredients but prove more economical and often as effective as lard oil.
(d) Sulfurized-Fatty-Mineral Oil.
Most good cutting oils contain
mineral oil and lard oil with various amounts of sulfur and chlorine, which
give the oils good antiweld properties and promote free machining.
These
oils play an important part in present-day machining because they provide
good finishes on most materials and aid the cutting of tough materials.
(e) Soluble Cutting Oils. Water is an excellent cooling medium but has
little lubricating value and hastens rust and corrosion. Therefore, mineral
oils or lard oils which are mixable with water are often mixed with water to
form a cutting oil.
Soluble oil and water has lubricating qualities
depending upon the strength of the solution.
Generally, soluble oil and
water is used for rough cutting where quick dissipation of heat is most
important.
Borax and trisodium phosphate are sometimes added to the
solution to improve its corrosion resistance.
(f) Soda-Water Mixtures. Salts such as soda ash and trisodium phosphate
are sometimes added to water to help control rust.
This mixture is the
cheapest of all coolants and has practically no lubricating value. Lard oil
and soap in small quantities are sometimes added to the mixture to improve
its lubricating qualities. Generally, soda water is used only where cooling
is the prime consideration and lubrication is secondary. It is especially
suitable in reaming and threading operations on cast iron where a better
finish is desired.
(g) White Lead And Lard Oil Mixture.
White lead can be mixed with
either lard oil or mineral oil to form a cutting oil which is especially
suitable for difficult machining of very hard metals.
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