Workshop Technology
Extrusion

Consists of pressing the metal inside a chamber to force it out by high pressure through an orifice which is shaped to provide the desired form of the finished part
Is extensively used for making bolts and nuts
Is used to improve fatigue resistance of the metal by setting up compressive stresses in its surface
Is used for reducing the diameter of round bars and tubes by rotating dies which open and close rapidly on the work

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Workshop Technology
Riddle is used for

Moistening the sand around the edge before removing pattern
Cleaning the moulding sand
Smoothing and cleaning out depressions in the mould
Reinforcement of sand in the top part of moulding box

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