Chapter 42met33800/9_Chapter_42/Chapter_42.pdf · chapter 42 - 74 broaching manufacturing methods...
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10/16/2014 1 Before you begin: Turn on the sound on your computer. There is audio to accompany this presentation. Chapter 42 Thread and Gear Manufacturing MET 33800 Manufacturing Processes THREAD MANUFACTURING Screw Thread Ridge of uniform section in the form of a helix on the external or internal surface of a cylinder (straight thread) or in the form of a conical spiral on the frustum of a cone (taper thread). Chapter 42 - 2 Unified and American Screw Thread Standards (1948) H28 Handbook adopted by U.S., Canada, and Great Britain. International Organization for Standards (1968) ISO/R68-1969, metric standards SCREW THREAD STANDARDS Chapter 42 - 3
Transcript of Chapter 42met33800/9_Chapter_42/Chapter_42.pdf · chapter 42 - 74 broaching manufacturing methods...
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Before you begin: Turn on the sound on your computer. There is audio to accompany this presentation.
Chapter 42
Thread and Gear Manufacturing
MET 33800 Manufacturing Processes
THREAD MANUFACTURING
Screw Thread
Ridge of uniform section in the form of a helix on the external or internal surface of a cylinder (straight thread) or in the form of a conical spiral on the frustum of a cone (taper thread).
Chapter 42 - 2
Unified and American Screw Thread Standards (1948) H28 Handbook adopted by U.S., Canada, and Great Britain.
International Organization for Standards (1968) ISO/R68-1969, metric standards
SCREW THREAD STANDARDS
Chapter 42 - 3
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SCREW THREAD STANDARDS
Chapter 42 - 4
1. Pitch distance from a point on one screw thread to the corresponding point on the next thread.
2. Threads per Inch TPI = 1 pitch
3. Pitch Diameter diameter at which thread form width equals thread form separation.
NOMENCLATURE
Chapter 42 - 5
NOMENCLATURE
Chapter 42 - 6
Pitch Diameter
Pitch Line
Pitch
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4. Major Diameter:
External – crest
Internal – root
5. Minor Diameter:
External – root
Internal – crest
NOMENCLATURE
Chapter 42 - 7
6. Lead axial advance of thread per revolution.
Lead = pitch for single lead thread.
7. Root usually radius to relieve stress.
8. Helix Angle angle of thread form from perpendicular to axis.
9. Thread Angle included angle of thread form.
NOMENCLATURE
Chapter 42 - 8
NOMENCLATURE
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10. Class manufacturing tolerances:
Class 1 special applications (ordnance)
Class 2 normal production grade
Class 3 minimum clearance
11. Designator:
A external thread
B internal thread
NOMENCLATURE
Chapter 42 - 10
¼ - 20 UNC – 3A
Nominal Size
Threads per Inch
Thread Series
Thread Class
NOMENCLATURE
Chapter 42 - 11
1. Coarse-thread series (UNC and NC) - general use.
2. Fine-thread series (UNF and NF) - automotive and aerospace.
3. Extra-fine-thread series (UNEF and NEF) - thin wall.
4. Eight-thread series (8UN and 8N) – pipe flanges, 1 to 6 inch diameter.
5. Twelve-thread series (12UN and 12N) - not used extensively, 1/2 to 6" diameter.
6. Sixteen-thread series (16UN and 16N) - fine thread applications, 3/4 to 6" diameter.
TYPES of SCREW THREADS
Chapter 42 - 12
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7. American Acme thread - used to transmit power and motion.
8. Buttress thread - used to transmit power and motion.
9. Square thread - used to transmit power and motion.
10.29 Worm thread - used to transmit power and motion.
11.American standard pipe thread - taper thread form.
TYPES of SCREW THREADS
Chapter 42 - 13
TYPES of SCREW THREADS
Chapter 42 - 14
External Threads
1. Single point threading on lathe manual or CNC
2. Thread die solid or solid-adjustable, usually hand threading
3. Die head self-opening used on lathes and screw machines
MANUFACTURING METHODS
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MANUFACTURING METHODS
Chapter 42 - 16
MANUFACTURING METHODS
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MANUFACTURING METHODS
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MANUFACTURING METHODS
Chapter 42 - 19
External Threads (continued):
4. Thread milling CNC machines
5. Thread grinding single or multiple form wheels
6. Thread rolling cold forming process, flat or cylindrical dies
MANUFACTURING METHODS
Chapter 42 - 20
MANUFACTURING METHODS
Chapter 42 - 21
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MANUFACTURING METHODS
Chapter 42 - 22
MANUFACTURING METHODS
Chapter 42 - 23
MANUFACTURING METHODS
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THREAD ROLLS
MANUFACTURING METHODS
Chapter 42 - 25
THREAD ROLLING
MANUFACTURING METHODS
Chapter 42 - 26
MANUFACTURING METHODS
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MANUFACTURING METHODS
Internal Thread Variations
Chapter 42 - 28
Internal Threads
1. Tapping hand, drill press, lathe, and CNC equipment
Taper tap (8) tapered (incomplete) threads for alignment.
Plug tap (4) tapered threads.
Bottoming tap (1 1/2) tapered threads.
Straight or spiral flute Controls direction of chip flow.
Standard point or spiral point Controls direction of chip flow.
MANUFACTURING METHODS
Chapter 42 - 29
MANUFACTURING METHODS
Chapter 42 - 30
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MANUFACTURING METHODS
Chapter 42 - 31
MANUFACTURING METHODS
Chapter 42 - 32
MANUFACTURING METHODS
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MANUFACTURING METHODS
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MANUFACTURING METHODS
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MANUFACTURING METHODS
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MANUFACTURING METHODS
Chapter 42 - 37
Tapping Heads:
Internal Threads (continued):
2. Collapsing taps similar to die head.
3. Single point threading on lathe boring bar.
4. Thread milling CNC machines.
5. Thread forming fluteless taps.
MANUFACTURING METHODS
Chapter 42 - 38
MANUFACTURING METHODS
Chapter 42 - 39
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MANUFACTURING METHODS
Chapter 42 - 40
Tap Drill Calculation:
TD = MD – [ 2(d) x 0.75 ]
where: TD = Tap Drill Diameter
MD = Major Diameter
d = Thread Depth = P x 0.6134
P = Pitch = 1/TPI
TPI = #Threads per Inch
MANUFACTURING METHODS
Chapter 42 - 41
Tap Drill Calculation: ¼-20 UNC-3B thread
TD = MD – [ 2(d) x 0.75 ]
d = P x 0.6134
P = 1/TPI
TD = 0.250 – [2(1/20)(0.6134) x 0.75]
TD = 0.204 (#6 Drill)
Example
Chapter 42 - 42
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L R L Rm
(L A A )n πD(L A A )nT
N 12V
Where: Tm = Cutting Time (min)L = Depth of Tapped Hole (in)n = Threads per Inch N = Spindle Speed (rpm)D = Tap Diameter (in)V = Cutting Speed (sfpm)AL = Start Allowance (in)AR = Withdraw Allowance (in)
MANUFACTURING METHODS
Chapter 42 - 43
Gear Manufacturing
Chapter 42 - 44
Gears Transmit power and motion mechanically.
Size range Microscopic to 30+ ft in diameter.
INTRODUCTION
Chapter 42 - 45
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1. Spur Gears straight teeth, parallel shafts.
2. Helical Gears tooth form at angle to axis of rotation, parallel and nonparallel shafts.
3. Rack gear with infinite radius, teeth lie on straight line.
4. Herringbone Gears double helix angle.
Continuous no center relief.
Modified groove or gap between helix pairs.
TYPES of GEARS
Chapter 42 - 46
5. Worm and Worm Gear type of screw thread in mesh with special gear tooth form.
6. Bevel Gear teeth form on conical form, straight or spiral-tooth.
7. Hypoid Gear spiral bevel gear not requiring common intersecting axes.
8. Zerol Gear bevel gear with teeth in circular arc.
9. Crown Gear tooth form in side of disk.
TYPES of GEARS
Chapter 42 - 47
TYPES of GEARS
Chapter 42 - 48
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TYPES of GEARS
Chapter 42 - 49
1. Pitch Circle - corresponds to effective diameter of gear, controls angular velocity.
2. Pitch Diameter (PD) - pitch circle diameter.
3. Pitch Point - point of intersection between gears in mesh, should be on pitch circle.
4. Involute Curve - Gear tooth form. Allows rolling motion rather than sliding motion.
NOMENCLATURE
Chapter 42 - 50
NOMENCLATURE
Chapter 42 - 51
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INVOLUTE CURVE
NOMENCLATURE
Chapter 42 - 52
5. Diametrical Pitch (DP) – number of teeth (N) per unit of pitch diameter (PD): DP = N/PD
6. Addendum – radial distance from PD to outside diameter: Addendum = 1/DP.
7. Dedendum – radial distance from PD to root circle.
8. Circular Pitch – distance between corresponding points on adjacent teeth. Circular Pitch = /DP
NOMENCLATURE
Chapter 42 - 53
NOMENCLATURE
Chapter 42 - 54
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9. Tooth Thickness - measured along pitch circle.
10. Face Width length of teeth in axial plane.
11. Tooth Face mating surface between pitch circle and addendum circle.
12. Tooth Flank mating surface between pitch circle and root circle.
NOMENCLATURE
Chapter 42 - 55
NOMENCLATURE
Chapter 42 - 56
1. Machining - multi-step process.
2. Cold-Forming - rolling process similar to thread method.
3. Extrusion
4. Casting - sand, die and investment casting used.
5. Blanking - punch press.
6. Powder Metallurgy - high quality.
7. Plastic Molding
8. Forging
9. Flame Machining
MANUFACTURING METHODS
Chapter 42 - 57
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1. Blanking – produces a semi-finished form ready for the gear cutting operation. Methods:
Turning.
Milling.
Grinding.
MANUFACTURING SEQUENCE
Chapter 42 - 58
2. Gear Cutting – forms gear tooth form. Methods:
Hobbing – Generating process. Hob has one tooth form wrapped around cylinder to form helix. Most common gear manufacturing process.
Milling – Form cutters with tooth shape utilized. Stocking cutter used for roughing cuts. Helical gears milled using dividing head. Special milling machines available.
MANUFACTURING SEQUENCE
Chapter 42 - 59
HOBBING
MANUFACTURING METHODS
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HOBBING
MANUFACTURING METHODS
Chapter 42 - 61
HOBBING
MANUFACTURING METHODS
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HOBBING
MANUFACTURING METHODS
Chapter 42 - 63
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MANUFACTURING METHODS
Chapter 42 - 64
HOBBING
MILLING
MANUFACTURING METHODS
Chapter 42 - 65
MILLING
MANUFACTURING METHODS
Chapter 42 - 66
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MILLING
MANUFACTURING METHODS
Chapter 42 - 67
MILLING
MANUFACTURING METHODS
Chapter 42 - 68
MILLING
MANUFACTURING METHODS
Chapter 42 - 69
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2. Gear Cutting (continued) – Methods:
Shaping – Generating process. Reciprocating cutter in form of tooth shape.
Broaching – Both internal and external gears.
Bevel Gear – Utilizes special machines.
Rolling – Cold-forming process.
Grinding – Wheels dressed into tooth form.
MANUFACTURING SEQUENCE
Chapter 42 - 70
SHAPING
MANUFACTURING METHODS
Chapter 42 - 71
SHAPING
MANUFACTURING METHODS
Chapter 42 - 72
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SHAPING
MANUFACTURING METHODS
Chapter 42 - 73
SHAPING
MANUFACTURING METHODS
Chapter 42 - 74
BROACHING
MANUFACTURING METHODS
Chapter 42 - 75
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BROACHING
MANUFACTURING METHODS
Chapter 42 - 76
SPECIAL MACHINES
MANUFACTURING METHODS
Chapter 42 - 77
GRINDING
MANUFACTURING METHODS
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GRINDING
MANUFACTURING METHODS
Chapter 42 - 79
GRINDING
MANUFACTURING METHODS
Chapter 42 - 80
3. Heat Treatment – required for wear, through hardening and surface hardening used.
4. Finishing – Finalize geometry and accuracy. Methods:
Shaving – Gear run at high speed in contact with shaving tool. Minimal stock removed.
Roll Finishing Cold-forming process for helical gears.
Grinding Wheel dressed with tooth form or straight wheel with gear rolling past.
Lapping Cast iron lapping gear.
MANUFACTURING SEQUENCE
Chapter 42 - 81
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FINISHING
MANUFACTURING METHODS
Chapter 42 - 82
The End – See Oncourse for Videos
Chapter 42 - 83
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