In tribological measurement of thermoplastics against steel the surface roughness has a potentialeffect in dictating the frictional behavior of the material. In most cases the roughness of the specimen ismeasured before and after the test, where it affects the friction force and influences the mechanisminvolved. The roughness of the material is not the exact value and it has a deviance which depends uponthe machining process used in preparing the surface. Generally, the direction of machining

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... s an influenceon the topography of the surface in case of turning, milling and drilling but in case of pressed componentsthe direction has no effects. In order to maintain ideal test condition the surface roughness of the testmaterials has to be consistent for the given number of samples. Even though the test specimens aremachined in the same machine with same parameters there are number of parameters involved in decidingthe consistency of the surface roughness. The roughness of the surface are defined by number ofparameters such as Ra, Rz and few 3D parameters in such a case narrowing down to a specific constant isvital. The results from the roughness is not made from one measurement were an average and deviancefrom several measurement decides that if two ideal samples has same or different roughness.