Lathe Operations: Facing

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Facing Operations Facing is the process of removing metal from the end of a workpiece to produce a flat surface. Most often, the workpiece is cylindrical, but using a 4-jaw chuck you can face rectangular or odd-shaped work to form cubes and other non-cylindrical shapes.

When a lathe cutting tool removes metal it applies considerable tangential (i.e. lateral or sideways) force to the workpiece. To safely perform a facing operation the end of the workpiece must be positioned close to the jaws of the chuck. The workpiece should not extend more than 2-3 times its diameter from the chuck jaws unless a steady rest is used to support the free end. Cutting Speeds

If you read many books on machining you will find a lot of information about the correct cutting speed for the movement of the cutting tool in relation to the workpiece. You must consider the rotational speed of the workpiece and the movement of the tool relative to the workpiece. Basically, the softer the metal the faster the cutting. D…

Types of Heat Treatment

Heat treatment is defined as an operation or combination of operations, involving heating and cooling of a metal or alloy in the solid state to obtain desirable properties.



Heat treatment consists of three phases.



(a)        Heating of the metal



(b)       Soaking of the heat into metal



(c)        Cooling of the metal



Heating.       Heating temperature of metal for the purpose of heat treatment depends upon its grade, grain size, type and shape of a metal or alloy. Generally, the metal is never heated much beyond its upper critical temperature. Plastic deformation takes place because of heating. This deformation depends upon the chemical composition of the metal or alloy and the temperature at which it is heated.



Soaking - Metal or alloy to be given heat treatment, is held at the specified temperature for a specified period so that there is a uniformity of temperature throughout the mass. The period of soaking depends upon the size and shape of the component.



Cooling - Main changes in the properties of metal or alloy take place in the cooling process. Change in properties or transformation depends mostly on the rate at which the cooling takes place. The different media used for cooling are,



(a)          Caustic Soda solution.



(b)          Brine solution (NaCl).



(c)          Water.



(d)          Oil.



(e)          Air.

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