Machining Operations

Machining Operations
In MACHINING, the shape, size, finish and accuracy are obtained by removing the excess material from the workpiece surface. Various surfaces are obtained as an interaction between a workpiece and a cutting tool with the help of a contrivance known as MACHINE TOOL.

Prof. S.K. Choudhury, Mechanical Engineering Department, IIT Kanpur

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Advantages and Disadvantages of Machining
Variety of work materials can be machined. o Most frequently used to cut metals Variety of part shapes and special geometric features possible, such as:  Screw threads  Accurate round holes  Very straight edges and surfaces  Good dimensional accuracy and surface finish  Generally performed after other manufacturing processes, such as casting, forging, and bar drawing Disadvantages: Wasteful of material and time consuming
Prof. S.K. Choudhury, Mechanical Engineering Department, IIT Kanpur 2

Basic Machining Parameters
Speed (V) [m/min] • Relates velocity of the cutting tool to the work piece (Primary motion). Feed (f) [mm/rev] • Movement (advancement) of the tool per revolution of the workpiece Depth of Cut (d) [mm] • Distance the tool has plunged into the surface

Prof. S.K. Choudhury, Mechanical Engineering Department, IIT Kanpur

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Chip Formation

Cutting action involves shear deformation of work material to form a chip. As chip is removed, new surface is exposed.

Prof. S.K. Choudhury, Mechanical Engineering Department, IIT Kanpur

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Cutting Tools & Types of Machining

A Typical Lathe Tool Wedge-Shaped tool

Orthogonal Cutting

Oblique Cutting
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Prof. S.K. Choudhury, Mechanical Engineering Department, IIT Kanpur

Tool Angles
Rake Angles (α) • Influence cutting forces, power and surface finish • Large α – lowers forces and improves surface finish – In general, power consumption ↓by ~ 1% for 1 degree change in α – Has adverse effect on tool strength because less metal is available to support the tool. – Greatly reduced