Mineral-Lard Cutting Mixture.

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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