1. Machining Operations Part 1: Chapters 21, 22
Manufacturing Processes, 1311
Dr Simin Nasseri
Southern Polytechnic State University

2. Material Removal Processes
A family of shaping operations, the common feature of which is removal of material from a starting workpart so the remaining part has the desired geometry.
Material Removal
Machining – material removal by a sharp cutting tool, e.g., turning, milling, drilling.
Abrasive processes – material removal by hard, abrasive particles, e.g., grinding.
Nontraditional processes - various energy forms other than sharp cutting tool to remove material, e.g. electrochemical and thermal energy processes.

3. Reasons to Machine Variety of work materials can be machined.
Most frequently used to cut metals.
Variety of part shapes and special geometric features possible,
Screw threads.
Accurate round holes.
Very straight edges and surfaces.
Improve dimensional accuracy of:
Castings, forming, or shaping processes.
Produce features that cannot be produced by forming and shaping processes.
External and internal profiles.
Sharp corners.
Flatness.
Remove distortion & discoloration from heat-treatment.
Reduce manufacturing costs (usually small quantities).
Apply special surface characteristics or textures.

4. Machining Limitations
Wasteful of material
Chips generated in machining are wasted material, at least in the unit operation
Time consuming
A machining operation generally takes more time to shape a given part than alternative shaping processes, such as casting, powder metallurgy, or forming
More expensive for mass production.
Consumes more energy.
Can have adverse effects on surface quality & properties.

5. Classification of Machined Parts
Rotational - cylindrical or disk‑like shape
Nonrotational (also called prismatic) - block‑like or plate‑like
Figure Machined parts are classified as: (a) rotational, or (b) nonrotational, shown here by block and flat parts.

6. Or combination of the two.
Machining Operations and Part Geometry
Each machining operation produces a characteristic part geometry due to two factors:
1- Relative motions between tool and workpart
Generating – part geometry determined by feed trajectory of cutting tool
2- Shape of the cutting tool
Forming – part geometry is created by the shape of the cutting tool
Or combination of the two.

7. Part geometry determined by feed trajectory of cutting tool.
Generating Shape
Part geometry determined by feed trajectory of cutting tool.
Figure Generating shape: (a) straight turning, (b) taper turning, (c) contour turning, (d) plain milling, (e) profile milling.

8. Forming to Create Shape
Part geometry is created by the shape of the cutting tool.
Figure Forming to create shape: (a) form turning, (b) drilling, and (c) broaching.

9. Forming and Generating
Part geometry determined by feed trajectory of cutting tool and is also created by the shape of the cutting tool.
Figure Combination of forming and generating to create shape: (a) thread cutting on a lathe, and (b) slot milling.

10. Machining Processes Planing Traditional Chip Removal
Nontraditional Machining
Ultrasonic
Electrical Discharge
Electro-arc
Optical Lasers
Electrochemical
Chem-milling
Abrasive Jet Cutting
Electron Beam Machining
Plasma Arc Machining
Turning
Milling
Drilling
Boring
Reaming
Shaping
Sawing
Broaching
Planing
Grinding
Honing
Lapping
In the following slides, guess the machining processes based on the information given!

11. Conventional Machining

12. Figure 21.3 Three most common machining processes: (a) turning,
Single point cutting tool removes material from a rotating workpiece to form a cylindrical shape

13. Figure 21.3 (b) drilling,
Drilling
Used to create a round hole, usually by means of a rotating tool with two cutting edges

14. Two forms: peripheral milling and face milling
Figure (c) peripheral milling (Axis of the tool is parallel to the surface), and (d) face milling (axis of the tool is perpendicular to the surface).
Milling
Two forms: peripheral milling and face milling
Rotating multiple-cutting-edge tool is moved across work to cut a plane or straight surface

15. Broaching
Broaching operation.
The tool is called a broach. The machine is called the broaching machine.
This process is performed using a multiple tooth cutting tool. The tool is moved linearly relative to the work.

16. Figure 22.14 Machining operations related to drilling: (a) reaming
Used to slightly enlarge a hole, provide better tolerance on diameter, and improve surface finish.

17. Boring
Internal turning operation which is performed on the inside diameter of an existing hole (Turning is performed on the outside diameter of an existing cylinder)
Boring!
Figure A vertical boring mill – for large, heavy workparts.

18. Counterboring
Provides a stepped hole, in which a larger diameter follows smaller diameter partially into the hole.
Figure Counterboring

19. Compare!
Reaming Counterboring Boring

20. Tapping Used to provide internal screw threads on an existing hole
Figure (b) tapping. Tool is called a tap
Tapping
Used to provide internal screw threads on an existing hole

21. Tool is called a saw blade
Sawing
Cuts narrow slit in work by a tool consisting of a series of narrowly spaced teeth.
Typical functions:
Separate a workpart into two pieces.
Cut off unwanted portions of part.
Sawing
Tool is called a saw blade

22. Shaping & Planing Shaping: Planing:
Tool has a linear speed motion. Work has occasional feed motion.
Planing:
Work has a linear speed motion. Tool has occasional feed motion.
Figure (a) Shaping (, and (b) planing.

23. Machinery
In the following slides, guess the name of each machine based on the machining operation!

24. Figure 22.7 Diagram of an engine lathe, showing its principal components.
Turning:

25. Vertical Boring Mill Boring:
Figure A vertical boring mill – for large, heavy workparts.
Vertical Boring Mill
Boring:

26. Drill Press Drilling: Upright drill press stands on the floor
Figure Upright drill press
Drill Press
Drilling:
Upright drill press stands on the floor
Bench drill similar but smaller and mounted on a table or bench

27. Radial Drill Drilling: Large drill press designed for large parts.
Figure Radial drill press (photo courtesy of Willis Machinery and Tools).
Radial Drill
Drilling:
Large drill press designed for large parts.

28. Horizontal Milling Machine
Figure (a) Horizontal knee-and-column milling machine.
Horizontal Milling Machine
Milling:
Axis of the tool is parallel to the surface of the part.

29. Vertical Milling Machine
Figure (b) Vertical knee‑and‑column milling machine
Vertical Milling Machine
Milling:
Axis of the tool is perpendicular to the surface of the part.

30. Figure 22.30 Components of a shaper.
Shaping:
The shaping machine is used to machine flat metal surfaces especially where a large amount of metal has to be removed.
Other machines such as milling machines are much more expensive and are more suited to removing smaller amounts of metal, very accurately.
As the disc rotates, the top of the machine moves forwards and backwards (reciprocating motion), pushing a cutting tool. The cutting tool removes the metal from work which is carefully bolted down.

31. Figure 22.31 Open side planer.
Planing:

32. Shaping and Planing Two operations which are similar.
Both use a single point cutting tool moved linearly relative to the workpart.
A straight, flat surface is created in both operations
Interrupted cutting
Subjects tool to impact loading when entering work
Low cutting speeds due to start‑and‑stop motion
Typical tooling: single point high speed steel tools
Figure (a) Shaping (, and (b) planing.

33. Figure 22.35 (a) Power hacksaw
Sawing:
Linear reciprocating motion of hacksaw blade against work.

34. Figure 22.35 (b) Bandsaw (vertical)
Sawing:
Linear continuous motion of bandsaw blade, which is in the form of an endless flexible loop with teeth on one edge.

35. Figure 22.35 (c) Circular saw
Sawing:
Rotating saw blade provides continuous motion of tool past workpart.

36. CNC 4‑axis turning center
Figure CNC 4‑axis turning center (photo courtesy of Cincinnati Milacron);
CNC 4‑axis turning center
Capable of turning and related operations, contour turning, and automatic tool indexing, all under computer control.