Lathe Operations: Facing

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…

Puddling Process of Wrought Iron

Wrought iron is virtually pure iron, containing a large number of minute threads of slag lying parallel to each other, thereby giving the metal a fibrous appearance when broken. It contains negligible carbon percentage and therefore, does not harden when quenched in water. Wrought iron is produced by puddling process in reverberatory furnace.

Puddling Process             

Wrought iron is produced in reverberatory furnace by puddling process which is similar to open hearth furnace with combustion taking place at one end only. The furnace is lined with iron oxide. (in the form of mill scale or ore).  Pig iron is   charged   into the furnace. The carbon present in pig iron is melted and eliminated by the iron oxide lining. When practically all of the carbon and other impurities have been eliminated, the metal has a higher melting point and begins to form into a pasty mass. This pasty mass of metal and slag is well stirred (puddling) and formed into a bar, which is then removed from the furnace. The bulk of the slag is then squeezed from this mass by means of a mechanical squeezer and the iron is then rolled into bars. Now the material is a mixture of high purity iron and some slag (about 0.7%).

Composition of Different Types of Iron

Type of IronCarbon%Sulphur%Silicon%Manganese%Phosphorus%Iron%
Pig Iron1-4.5<11-20.1-1.50.5-295-96
Grey Cast iron2.5-
White Cast Iron4.50.10.5-1.50.2-0.80.1894
Mottled Cast Iron.3.500.750.750.750.7593.5
Nodular cast iron3.2-4.1<0.031-2.780.3-0.8<0.1094.5
Malleable cast iron2.2-2.80.03- 0.10.7- 1.10.3 - 0.40.1097.5
Wrought Iron0.02-0.030.08-0.020.02-


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