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Tribology, Surface Roughness in Machining – Lesson Summary

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Chip - Tool Tribology


During the late 1970's a transparent sapphire tool is constructed to study the chip process. There are two zones of contact: 




Sticking Zone: The chip material sticking to the rake face of the tool
Sliding Zone: The chip material sliding across the rake surface of the tool 




Lubrication in Machining


The process of lubrication is helping the surface to separate and reduce the resistance in the interface. 


The three types of basic lubrication mechanisms are:


Boundary Lubrication
Mixed Lubrication
Hydrodynamic Lubrication

 
Surface Roughness


A numerical assessment of surface roughness can be carried out by the number of ways. These numerical values are obtained with respect to a datum. 


The following methods are used for obtaining primary roughness of a surface:


Peak to valley height method 
The average roughness
Bearing Curve 




Material Removal Rate (MRR)


Material Removal Rate (MRR) in metal cutting indicates the volume of chips being removed from the workpiece per unit time (MRR = Volume Removed / Time).                                                                                           


Machinability 


Machinability is the ease in which the materials can be machined. Machinability depends on the physical properties and the cutting conditions of the material.