1. Manufacturing Rounded Shapes II
Manufacturing Processes

2. Outline Specialized Turning Operations Cutting Screw Threads Knurling
High-Speed Machining
Ultraprecision Machining
Hard Turning
Cutting Screw Threads
Knurling
Boring and Boring Machines
Drilling and Drills
Reaming and Reamers
Tapping and Taps
Chip Collection

3. High-Speed Machining
Decreases cutting time by increasing cutting speed
Approximate Range of Cutting Speeds:
High Speed: ft/min
Very High Speed: ft/min
Ultrahigh Speed: >60000 ft/min
Decreases total energy required:
- Power for high-speed machining ≈ .004 W/rpm
Power for normal machining
≈ W/rpm
Most important when cutting time is a significant part of the manufacturing time

4. High-Speed Machining Factors: Stiffness of the machine tools
Stiffness of tool holders and workpiece holders
Proper spindle for high speeds and power
Sufficiently fast feed drives
Automation
A proper cutting tool for high cutting speeds
Ability to hold the piece in fixtures at high speed

5. Ultraprecision Machining
Used for very small surface finish tolerances in the range of µm
The depth of cut is in the range of nanometers
Machine tools must be made with high stiffness

6. Ultraprecision Machining
Factors:
Stiffness, damping, and geometric accuracy of machine tools
Accurate linear and rotational motion control
Proper spindle technology
Thermal expansion of machine tools, compensation thereof, and control of the machine tool environment
Correct selection and application of cutting tools
Machining parameters
Performance and tool-condition monitoring in real time, and control thereof

7. Hard Turning Used for relatively hard, brittle materials
Produces parts with good dimensional accuracy, smooth surface finish, and surface integrity
May be used as an alternative to grinding

8. Hard Turning Procedure

9. Hard Turning Statistics
Heat dissipated by chips
Tool forces: radial force is greatest

10. Hard Turning Chip Formation
Brittle materials form segmented chips, which cause a large force against the cutting edge

11. Hard Turning Advantages (as an alternative to grinding)
Lower cost of machine tools
Ability to machine complex parts in a single setup
Ability to create various part styles or small part numbers efficiently
Less industrial waste
Ability to cut without fluids (eliminates grinding sludge)
Easily automated

12. Hard Turning Surface Finish
NO YES
A hard journal bearing surface should have a surface with deep valleys and low peaks

13. Cutting Screw Threads
Cutting threads on a lathe is slower than newer methods
Die-Head Chasers
used to increase production rate of threading on a lathe
Solid Threading Dies
used for cutting straight or tapered threads on the ends of pipes or tubing

14. Cutting Screw Threads

15. Cutting Screw Threads

16. Die-Head Chasers and Solid Threading Dies
Straight chaser cutting die (top)
Circular chaser cutting die (bottom left)
Solid threading die (bottom right)

17. Screw Machine

18. Screw Machine

19. Cutting Screw Threads Design Considerations:
Threads should not be required to reach a shoulder
Avoid shallow blind tapped holes
Chamfer the ends of threaded sections to reduce burrs
Do not interrupt threaded sections with slots, holes etc.
Use standard thread tools and inserts as much as possible
The walls of the part should be thick enough to withstand clamping and cutting forces
Design the part so that cutting operations can be completed in a single setup

20. Knurling
Used to create a uniform roughness pattern on cylindrical surfaces
Performed on parts where friction is desired (knobs, grip bars etc.)
Types:
Angular Knurls
create a pattern of diamond-shaped ridges
Straight Knurls
create a pattern of straight longitudinal ridges

21. Knurling Results

22. Knurling Operation

23. Boring and Boring Machines
Boring produces circular internal profiles
Small pieces can be bored on a lathe; boring mills are used for larger workpieces

24. Boring Operation

25. Boring Operation

26. Boring and Boring Machines
Design Considerations:
Avoid blind holes when possible
A higher ratio of the length to the bore diameter will cause more variations in dimensions because the boring bar will deflect more
Avoid interrupted internal surfaces

27. Drilling and Drills Types of drill Twist drill (most common) Gun drill
Trepanner
Pilot Holes
Sometimes, when drilling large-diameter holes, it is necessary to drill a smaller hole first to guide the large drill

28. Types of Drills and Drilling Operations

29. Drill Terminology

30. stainless steel, titanium
Drill Point Angle
Point Angle
118° Standard
135° Harder Materials
stainless steel, titanium
Minimizes burring
90° Softer Materials
plastic

31. Trepanners

32. Drills and Drilling Deep Holes
Complications may occur when drilling a hole longer than 3 times the drill diameter
Problems
Chip removal
Coolant dispensing to the cutting edge
Tool deflection

33. Drills and Drilling Small Holes Small drills .0059-.04 in
Microdrilling in

34. Microdrills

35. Pilot Holes

36. Drills and Drilling Forces and Torque Thrust force:
acts perpendicular to the axis of the hole; large forces can cause the drill to bend or break
Torque:
the torque acting to turn the drill
These values are difficult to calculate

37. Drill Feed and Speed V = πDN/12 V = cutting speed in ft/min;
Velocity at which the drill edge moves along the workpiece surface
D = diameter of the drill
N = RPM of the drill
Feeds for drills are listed as in/rev or m/rev. Multiply these by the RPM to obtain the feed in in/min or m/min. The feed cannot be controlled accurately on a drill press fed by hand.

38. Drill Feed and Speed

39. Drill Feed and Speed Example: Work Material: Aluminum
Tool Material: High Speed Steel
Drill Diameter: .5 in
Recommended Cutting Speed: ft/min (from table)
N = 12V/πD
N=12*( )/(π*.5)
= RPM
Recommended Feed for aluminum, .5in = in/rev (from table)
f = ( )*1528 RPM = in/min

40. Drilling Material Removal Rate
MRR = (πD2/4)f N
D = drill diameter
f = feed, in/rev or mm/rev
N = RPM

41. Drilling Material Removal Rate
Example:
Drill Diameter: .5 in
Feed: in/rev
RPM: RPM
MRR = (πD2/4)f N
= (π(.5)2/4).006*1528
= 1.8 in3/min

42. Drilling Operation

43. Reaming and Reamers
Used to improve the dimensional accuracy or surface finish of an existing hole
Types of reamers
Hand reamers
Rose reamers
Fluted reamers
Shell reamers
Expansion reamers
Adjustable reamers

44. Types of Reamers

45. Reamer Terminology

46. Tapping and Taps Used to make internal threads in workpiece holes
Types of taps
Tapered taps
Bottoming taps
Collapsible taps

47. Tap Terminology

48. Drilling, Reaming and Tapping
Design Considerations:
Holes should be drilled on flat surfaces perpendicular to the hole axis to prevent drill deflection
Avoid interrupted hole surfaces
The bottoms of blind holes should match standard drill point angles
Avoid blind holes when possible; if large diameter holes are to be included, make a pre-existing hole in fabrication
Design the workpiece so as to minimize fixturing and repositioning during drilling
Provide extra hole depth for reaming or tapping blind or intersecting holes

49. Summary
Specialized cutting procedures exist for unusual materials and requirements
Proper procedure, securing of the workpiece, and feeds and speeds must be considered to prevent damage and injuries

50. T h e
E n d