1. Fasteners Chapter 5

2. Fasteners Objectives Describe USC threaded-fastener measuring system
Describe metric threaded measuring system
Identify grade markings of threaded fasteners
List and describe common thread repair tools

3. Objectives
Identify and explain purpose of common nonthreaded fasteners
Explain importance of wire gauge sizes
Identify common types of electrical fasteners

4. Introduction Automotive components are held together with fasteners
Much of a technician’s time is spent removing and installing fasteners
There are two basic groups
Threaded
Non-threaded

5. Threaded Fasteners Most common type of fastener
Use spiral threads to wedge parts together
Fastener Sizing and Torquing
Must be correct strength and size
Must be replaced with like size and quality
Never install a heavier sheer pin to “fix” a problem

6. Threaded Fasteners Screws One of the most common threaded fasteners
Fits into a threaded hole
Different designs to meet attaching needs
Some require a wrench to install, others can be installed with screwdrivers
Often classed by shape of head

8. Threaded Fasteners Bolts Use a nut instead of a threaded hole
Usually goes through parts that don’t have threads
Most have hex-shaped head
Two different types
Standard
Torque-to-yield

9. Threaded Fasteners Studs Nuts
Fastener with no head and threads on both ends
Nuts
Used with bolts and studs
Many different designs
Can be specialized to specific applications

11. Torque-to-Yield Bolt Installation
Follow all manufacturer instructions on torquing the bolt
Typically first two steps involve an actual ft.lbs reading on a torque meter

12. Torque-to-Yield Bolt Installation
Final step requires tightening the fastener a specified number of degrees
Greatly reduces effect of friction on torque readings

13. Threaded Fasteners Washers Often used to distribute loads
Prevent a nut from becoming loose
Prevent damage to a machined surface

14.                                   
Washers
Flat
Spring Lock
External tooth lock
Internal tooth lock

15. Nuts

17. Threaded Fasteners U.S. (English) Thread Sizes
Manufactured to Unified System specifications in Fractions of an Inch
Threads can be course or fine depending on the number of threads per inch
Bolt size is determined by shank diameter, bolt length, and threads per inch

18. Bolt Identification (Cont’d)

19. Bolt Identification Diameter Thread pitch (English system)
Measured across the threaded area
Thread pitch (English system)
The number of threads per inch
Thread pitch (Metric system)
The distance in millimeters between two adjacent threads

20. Metric Size Bolt Identification Example
A metric size bolt that is identified as
6mm x 30mm x 1.25mm:
Has a shank diameter of 6 millimeters.
Is 30 millimeters long from the bottom of the head to the end of the shank.
Has a distance of 1.25 millimeters between its threads.

21. Imperial Size Bolt Identification Example
An Imperial size bolt that is identified as 3/8" x 2" x 24:
Has a shank diameter of 3/8 inch.
Is 2 inches long from the bottom of the head to the end of the shank.
Has 24 threads per inch.

23. Threaded Fasteners Metric Thread Sizes
Same basic measurements as U.S. (English) bolts
Pitch number differentiates between fine and coarse as opposed to NC or NF ratings

24. Measuring Devices (Cont’d)
Screw pitch gauge / Thread pitch gauge
Is used to determine thread pitch of a bolt or screw.
Machinist’s rule
Is usually used to measure items that don’t require extremely close tolerances, such as bolt lengths

28. Bolt Grade Markings Customary (inch) bolts Metric bolts
Identification marks correspond to bolt strength.
Increasing numbers represent increasing strength.
Metric bolts
Identification class numbers correspond to bolt strength.
Metric and SAE size wrenches are not interchangeable.

29. Threaded Fasteners Hardness and Strength
Strength is identified by grade markings on the bolt head
Standards are set by the Society of Automotive Engineers (SAE)
Tensile strength is amount of pressure the fastener can take before it breaks

30. Grade Markings

31. Threaded Fasteners Fastener Torque
Must be tightened to the correct amount
Not enough torque causes fastener to loosen
Too much leads to breakage

32. Torque Wrenches

33. Thread Repair Tools Tap and Die Set Heilicoil
Thread Restorer and Chasers
Screw Extractor or EZ-Out (Brand Name)

34. Thread Repair Tools Tap and Die Sets
Dies are used to make external threads
Taper taps must extend through hole to work properly
Bottoming taps thread to bottom of hole

35. Thread Repair Tools Helicoils
Threaded device threads into a hole and provides internal threads for a bolt
Must be used in conjunction with a properly sized drill and tap

36. Heilicoil

37. Thread Repair Tools Thread Restorers and Chasers
Restoring files are used to smooth and shape damaged threads
Thread chasers fit over the damaged thread like a fastener
Turned back and forth over damaged threads until repaired

38. Thread Restorer files

39. TAP

44. Screw Extractor-EZ Out

46. Nonthreaded Fasteners
Snap Rings
Often used to hold parts in place on a shaft
Made from high quality steel that retains its shape
Snap rings can be internal or external

48. Electrical Wire
Replacement wire must be at least as heavy as the wire being repaired
Always try to match wire color
Use diagrams to pinpoint wire purpose before repairing

49. Electrical Wire size

50. Wire Sizes

51. Wire Crimpers

52. Connectors Two types of connectors-Solder and solderless Soldering
Best repair method for wires
Adds little or no resistance to circuit
Use only resin based solder in automotive circuits Acid based solder can add resistance to circuit.
Terminal Connectors
Device fastened to end of wire, allowing connection to a component
Most are covered with an insulator

53. Connectors Molded and Shell Connectors Many different shapes and sizes
Matched in color, shape, purpose to help prevent crossing circuits

54. Wire Connectors

55. Connectors Butt Connectors Connects two wires together
Quick and easy to install, but may add resistance

56. Nonthreaded Fasteners
Keys
Used to retain a part on a shaft
Fits into a slot called a keyway
Locks the two parts into position

57. Nonthreaded Fasteners
Splines
Long teeth are formed onto inside or outside of a part
Matching part has splines on opposite side

58. Nonthreaded Fasteners
Rivets
Used to hold parts together that are hardly ever disassembled
Made from soft materials
Rivets are removed by a drill or chisel
Then drive shaft out with a punch

59. Rivets

60. Summary
Threads are measured and classified using U.S. (English) or metric system
Fasteners must be used as designed
Nonthreaded fasteners are also common
Electrical terminals and wiring must be maintained