CHESTER Craftsman, Instruction Manual

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Cutting Fluid & Lubricant
The aims in metal cutting are to retain accuracy, to get a good surface finish on the work piece and at the
same time to have a longer tool life.
However during the metal cutting process heat is generated due to:
·
the deformation of the material ahead of the tool
·
friction at the tool point
Using a lubricant can readily reduce heat generated due to friction. Heat caused by deformation cannot
be reduced and yet a fluid can carry it away. Thus the use of a cutting fluid will serve to reduce the tool
wear, give better surface finish and a tighter dimensional control.
The proper selection, mixing and application of cutting fluids is however often misunderstood and
frequently neglected in machining practice. In order that the cutting fluid performs its functions properly it
is necessary to ensure that the cutting fluid be applied directly to the cutting zone so that it can form a
film at the sliding surfaces of the tool.
Cutting fluids in common use
Water
It has a high specific heat but is poor in lubrication and also encourages rusting. It is used as a cooling
agent during tool grinding.
Soluble Oils
Oil will not dissolve in water but can be made to form an intimate mixture or emulsion by
adding emulsifying agents. The oil is then suspended in the water in the form of tiny
droplets. These fluids have average lubricating abilities and good cooling properties.
Soluble oils are suitable for light cutting operations on general­purpose machines where
high rates of metal removal are often not of prime importance. There are many forms of
soluble oil in the market and the supplier’s instruction should be followed regarding the
proportions of the `mix'.
Mineral Oils
They are used for heavier cutting operations because of their good lubricating properties
and are commonly found in production machines where high rates of metal removal are
employed. Mineral oils are very suitable for steels but should not be used on copper or its
alloys since it has a corrosive effect.
Vegetable Oils
They are good lubricants but are of little used since they are liable to decompose and smell
badly.
Chester UK Craftsman Lathe
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