Neat oils, cutting fluids

Some of the recently developed high-performance EP soluble oils have a cutting performance that almost matches that of additive-type neat oils, and they are particularly suitable for demanding operations in machine tools whose design allows the use of water-based fluids. 

Neat oil is the name given to an orthodox petroleum cutting fluid, whether or not it contains additives, to enhance cutting properties. Oils of this sort are available in a very wide variety, and many combinations of work piece material, machining characteristics and tooling requirement justify special formulations. The neat oils have lower specific heat than water, so they have to be fed to the cutting zone in copious amounts to provide the optimum cutting effect. 

For the more difficult operations, neat oils containing EP (extreme-pressure) additives have to be used. The EP cutting oils usually contain additives based on sulfur or chlorine, or combinations of them. The sulfur in EP oil can be present in two forms. In the inactive fluid, it is chemically combined with a fatty-oil additive, which is blended with mineral oil to produce sulfured fatty oil. The active version, on the other hand, contains sulfur in elemental form, dissolved in mineral oil the fluid is known as sulfured mineral oil. Chlorine is usually present only as chlorinated paraffin, which is blended sometimes singly with mineral oils and sometimes in combination with fatty oils and sulfured additives. 

Cutting fluids may be classified as insoluble (neat or straight) oils and soluble oils (Table 2). The soluble oils are soluble in water and divided into synthetic, semisynthetic and so-called soluble or emulsifiable oils. 

Two factors militate against the universal use of water-based fluids. Very severe machining operations call for a lubrication performance that is beyond the capacity of such fluids, and the design of some machine tools means that water cannot be used because of the risk of cross-contamination with machine lubricants. In these instances, neat cutting oil is the only fluid that can provide the required performance. 

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