Course Content:

Mechanics of chip formation, chip curl. Bluntness and cutting forces. Thermal aspects of machining. Tool wear, tool life and economics of machining. Mechanics of grinding, forces and specific energy, temperature. wheel wear and surface finish.

Lecturewise Breakup (based on 50min per lecture)

I. Introduction: (2 Lectures)

Machining; Plastic Deformation, Tensile Test, Stress and Strain; Mechanism of Plastic Deformation: Slips, defects, plastic deformation on atomic scale.

II. Machining Process: (2.5 Lectures)

Types of machining processes; Chip formation; Orthogonal and Oblique Cutting; Types of Chips; Built-up edge formation.

III. Tool Geometry: (4 Lectures)

Reference planes; Tool specification: American System (ASA), continental or Orthogonal System (ORS), International or Normal Rake system (NRS); Tool angle relationships in ORS, ASA and NRS; Selection of Tool Angles; Multiple-point cutting tools: twist drill, helical milling cutter.

IV. Mechanics of Metal Cutting: (4.5 Lectures)

Merchant's Circle Diagram; Co-efficient of Friction: Determination of stress, strain and strain rate; Measurement of shear angle; Thin Zone model: Lee and Shaffer's Relationship; Thick Zone model: Okushima and Hitomi Analysisc.

V. Friction in Metal Cutting: (3 Lectures)

Nature of sliding friction; Friction in Metal Cutting: Sticking and Sliding Zones, Analysis of Stress Distribution on the tool face: Zorev’s model; Determination of mean angle of friction.

VI. Mechanism of Oblique cutting: (5 Lectures)

Rake angles in oblique cutting: Analytical determination of Normal Rake angle, velocity rake angle and effective rake angle; their relationship; shear angles in oblique cutting; velocity relationship; Force relationships in oblique cutting.

VII. Practical Machining Operations: (3.5 Lectures)

Turning, shaping and planning, Slab milling, Drilling: Machining Parameters, force magnitudes, power consumption, material removal rate, time per pass.

VIII. Measurement of cutting Forces: (2 Lectures)

Basic methods of measurement: Axially Loaded members, Cantilever Beam, Rings and Octagon, dynamometer requirements; machine tool dynamometers.

IX. Laboratory experiments on turning and grinding: (3 Lectures)

Tool angles; Measurement of cutting forces in turning and grinding; Measurement of temperature; chip thickness ratio; grain concentration in grinding.

IX. Tool Material, Tool Wear and Tool Life: (4 Lectures)

Types of tool wear; Mechanisms of wear: Abrasion, Adhesion and Diffusion. Progressive tool wear: flank and crater wear. Tool Life: variables affecting tool life - cutting conditions, tool geometry, Types of tool materials, fabrication of cutting inserts, coatings, work material and cutting fluid; Machinability and their criteria.

X. Economic of Machining: (2.5 Lectures)

Minimum Production Cost Criterion; Maximum Production Rate Criterion, and Maximum Profit Rate Criterion. Restrictions on cutting conditions: maximum power restriction, speed restriction, force and vibration restriction, surface finish restriction.

XI. Thermal Aspects of Machining: (2 Lectures)

Distinct regions of heat generation; Equations of Heat Flow: heat Flow due to conduction, heat flow due to transportation, heat absorbed and heat generated; Average Shear Plane temperature; Average Chip-tool interface Temperature; Experimental determination of cutting temperatures.

XII. Abrasive Machining Process: (3.5 Lectures)

Introduction: Types of abrasive machining processes; Grinding; types and characteristics; characteristics and specification of grinding wheels; Mechanics of Grinding Process; Determination of chip length in Grinding; Size effect; Wheel wear; Thermal Analysis; Honing and Lapping.

XIII. Term Paper:

Submission of soft and hard copies: presentation.

References:

1. E.J.A. Armarego and R.H.Brown-The machining of Metals
2. G Boothroyd-Fundamentals of Metal Machining and Machine tools
3. A.Ghosh and Asok Mallik- Machining Science
4. G.K.Lal and S.K.Choudhury-Fundamental of Manufacturing Processes
5. M.C.Shaw-Metal Cuttting Principle