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Types of mechanical forces

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A force exerted on a body can cause a change in either the shape or the motion of the body.The unit of force in SI system is the Newton(N) and CGS system is dyne.No solid body is perfectly rigid and when force are applied to it,changes in dimension occur.such changes are not always perceptible to the human eye since they are negligible. For the example,The span of a bridge will sag under the weight of a vehicle and a spanner will bend slightly when tightening a nut. It is also important for civil engineers and designers to appreciate the effects of forces on materials.Together with their mechanical properties of the materials. There three main types of mechanical forces that can act on a body.They are 1)Tensile force 2) compressive force and 3) shear force
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PRINCIPLE OF BROACHING MACHINE:

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In broaching, the broach is pushed or pulled over a external flat surface of a stationary workpiece. In internal broaching the broach is pushed or pulled through the hole in the stationary workpiece.In certain machines,the braich is held stationary and the workpiece translates over the broach.For broaching no separate feed is required as the feeding action is in built in the teeth form.Each successive tooth is a little higher than the one preciding it.Therefore each tooth removes a layer of workpiece material.The first fee teeth on broach are low to permit the small end of the tool to be passed through work.The intermediate teeth remove the most of the metal; and the last few teeth finish the surface to size machining operation completes in one pass of the broach.The cutting action of broach teeth is shown in fig.


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ADVANTAGES AND LIMITATIONS OF BROACHING:

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Broaching is an interesting machining process which is used in mass production. It has certain advantages and limitations as compared to the other machining processes.these are given below. ADVANTAGES : 1) Fast and simple process. 2)High degree of accuracy and finish is possible. 3)Any shape of profile can be easily machined. 4) Machining process is completed with one stroke of broach. 5) Life of broach tool is high. 6)Cutting temperature and tool wear is low. 7) Doesn't require a highly skilled operator. 8)Cutting force acts in the clamping direction I.e.,it doesn't tends to lift the workpiece from fixture. 9)cutting fluids can be applied more easily and effectively. 10)Most economical for mass production of components. LIMITATIONS: 1) Not economical for small quantity productions. 2)Cost of broach is high. 3) Tool grinding (broach sharpening) is difficult and expensive. 4) Not suitable to machine a surface having obstruction. 5) The work m
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