1. Modern Automotive Technology PowerPoint for by Russell Krick
Publisher The Goodheart-Willcox Co., Inc. Tinley Park, Illinois

2. Chapter 9
Fasteners, Gaskets,
Seals, and Sealants

3. Contents Fasteners Washers Machine screws Sheet metal screws
(9 Topics)
Fasteners
Washers
Machine screws
Sheet metal screws
Nonthreaded fasteners

4. Contents Torquing bolts and nuts Thread repairs
Removing damaged fasteners
Gaskets and seals

5. Fasteners Devices that hold the parts of a vehicle together
Thousands of fasteners are used in vehicles

6. Automotive Fasteners

7. Bolts and Nuts
Bolt
metal rod with external threads on one end and a head on the other
when a bolt is threaded into a part other than a nut, it can also be called a cap screw
Nut
has internal threads and, usually, a six-sided outer shape

8. Bolts and Nuts
When a nut is screwed onto a bolt, a powerful clamping force is produced

9. Bolt Dimensions

10. Bolt Dimensions

11. Thread Types There are three basic types of threads used on fasteners:
Coarse threads
UNC-Unified National Coarse
Fine threads
UNF-Unified National Fine
Metric threads SI

12. Thread Direction Bolts and nuts come in right- and left-hand threads
Right-hand threads
fastener must be turned clockwise to tighten
Left-hand threads
fastener must be turned counterclockwise to tighten
letter L may be stamped on fastener

13. Bolt Grade Also called tensile strength
Refers to the amount of pull a fastener can withstand before breaking
Bolt head markings specify the tensile strength of the bolt
U.S. customary bolts are marked with lines
Metric bolts are marked with numbers

14. Gives information about the bolt
Bolt Description
Gives information about the bolt

15. Used when purchasing new bolts
Bolt Description
Used when purchasing new bolts

16. Bolt Description

17. Common types of nuts used in vehicles
Nut Types
Common types of nuts used in vehicles

18. Castle Nut and Cotter Pin
Cotter pin keeps the nut from turning and possibly coming off

19. Washers Used under bolt heads and nuts
Two basic types of washers are used:
flat washers
lock washers

20. Washer Types Flat washer Lock washer
increases the clamping surface under the fastener
prevents the bolt or nut from digging into the part
Lock washer
prevents the bolt or nut from becoming loose under stress and vibration

21. Washer Types Lock tabs or lock plates
perform the functions of both flat washers and lock washers
increase clamping surface area and secure the fastener

22. Washer Types
A. Plain flat washer B. Split lock washer C. Toothed lock washer D. Lock plate

23. Machine Screws
Similar to bolts, but they normally have screw-type heads
Threaded along their full length
Used to secure parts when clamping loads are light
Available in various head shapes

24. Sheet Metal Screws Also called tapping screws
Commonly used on plastic and sheet metal parts, such as body trim, dashboard panels, and grills
Use tapering threads that are widely spaced

25. Sheet Metal Screws

26. Nonthreaded Fasteners
Numerous types of nonthreaded fasteners, such as snap rings, clips, and adhesives, are used in the assembly of a vehicle

27. Snap Ring
Fits into a groove in a part and commonly holds shafts, bearings, gears, pins, and other components in place
Snap ring pliers are needed to remove and install a snap ring
special jaws grasp the snap ring

28. Snap Ring Types

29. Keys and Set Screws Key Set screw
prevents a part from turning on its shaft
fits into a keyseat (slot) cut into a shaft and a keyway cut into the mating part
Set screw
normally used to lock a part onto a shaft
not as strong as a key

30. Keys and Set Screws
A. Key B. Set screw

31. Splines Series of slots cut into a shaft and a mating part
Allow the gear or collar to slide on the shaft but still not rotate
Used in manual transmissions, clutches, and drive shaft yokes

32. Splines

33. Adhesives Special glues widely used in vehicles
Used to hold body moldings, rubber weather stripping, and body emblems
Some stay soft and pliable; others dry hard
Some take hours to dry; others dry in seconds
Observe all directions and safety precautions when using adhesives

34. Torquing Bolts and Nuts
It is very important that bolts and nuts be tightened properly—this is called torquing

35. Torque Specifications
Tightening values given by the auto manufacturer
Normally given for all precision assemblies, such as engines, transmissions, and differentials
Factory specifications should be used
general bolt torque chart may be used if factory specs are not available

36. Bolt Torque Chart

37. Torque-to-Yield
Requires a bolt to be tightened to a specific torque and then turned an additional number of degrees
Procedure stretches the bolt to its correct yield point, preloading the fastener for better clamping under varying conditions
New bolts may be required each time

38. Torque Stretch
Determined by measuring bolt length change while torquing the bolt
when building a racing engine, you can “mike” connecting rod bolts to measure the length before and after tightening
Too much stretch indicates bolt weakness
Not enough stretch may indicate thread problems affecting torque

39. Bolt Tightening Sequence
Used to make sure that parts are fastened evenly
Creates an even, gradual clamping force along the entire mating surface of the parts
Crisscross pattern is often recommended

40. Bolt Tightening Sequence
Service manual pattern for a cylinder head

41. Bolt Tightening Sequence
Service manual pattern for wheel lug nuts

42. Torque Wrench Rules Keep a steady pull on the wrench
Clean fastener threads
Avoid using swivel joints
When reading a torque wrench, look straight down at the scale
Use manufacturer’s specifications when available

43. Torque Wrench Rules
When manufacturer’s specs are not available, use general specs in a crisscross pattern
To avoid a false reading, pull only on the handle
Tighten bolts and nuts in four steps
Retorque when required
some assemblies must be retightened after operation and heating

44. Thread Repairs
Threaded holes in parts can become damaged, requiring repairs. A technician must be capable of repairing damaged threads quickly and properly.

45. Minor Thread Repairs
Minor thread damage includes nicks, partial flattening, and other less serious problems
Minor damage can be repaired with a thread chaser or a thread file
the thread chaser is run through or over the threads to restore them

46. Major Thread Repairs
Badly smashed or stripped threads may be repaired with either a tap or die
Tap
threaded tool for cutting internal threads in holes
Die
cuts external threads on metal rods, bolts, shafts, and pins

47. Tap and Die

48. Using a Tap and Die Hold the handle squarely with the work
Back the handle off to clean metal out of the threads
Use a taper tap to start the threads
Use a plug tap and a bottoming tap to cut the threads to the bottom of the hole

49. Tap and Die Rules Never force a tap handle or the tool may break
Keep the tap and die well oiled to ease cutting
Use coarse threads when threading or tapping into soft metal, like aluminum
coarse threads will hold better than fine threads

50. Tapping Oversize
When threads cannot be restored, the hole can be drilled and tapped oversize
Use a “drill and tap size chart” to choose a drill bit and tap
Drill the hole one size larger than the original hole
Cut new threads in the drilled hole
Use a larger bolt in the threaded hole

51. Thread Repair Insert
Used when the use of an oversize hole and fastener is not acceptable
Takes place of damaged internal threads
Allows the use of the original-size bolt

52. Using an Insert A. Drill the hole oversize B. Tap the hole oversize
C. Mount the insert on a mandrel
D. Thread the insert into the hole

53. Insert allows the use of the original-size bolt
Using an Insert
Insert allows the use of the original-size bolt

54. Damaged threads before a repair
Using an Insert
Damaged threads before a repair
Installed insert

55. Removing Damaged Fasteners
An automotive technician must be able to remove broken bolts, screws, and studs, as well as fasteners having rusted or rounded-off heads
Specific tools and methods are needed for removing problem fasteners

56. Removal Methods Grasp a rusted or rounded head with locking pliers
Use a stud puller or stud wrench
removes studs and bolts broken off above the surface of the part

57. Removal Methods
Cut a slot in the fastener with a hacksaw or weld on a nut to grasp
Use a hammer and punch
angle the punch so that blows from the hammer can drive out the broken fastener
Drill a hole almost as large as the inside diameter of the threads
use a tap or punch to remove the thread shell

58. Removal Methods Using a screw extractor
A. Drill a hole
B. Tap the extractor into the hole
C. Unscrew the extractor and bolt

59. Use rust penetrant to help ease turning and prevent fastener breakage
Removal Methods
Use rust penetrant to help ease turning and prevent fastener breakage

60. Gaskets and Seals
Used between parts to prevent leakage of engine oil, coolant, transmission fluid, and other fluids

61. Gaskets
Soft, flexible material placed between parts to prevent leakage
Made of fiber materials, rubber, neoprene (synthetic rubber), cork, treated paper, or thin steel
When parts are fastened together, the gasket material fills small gaps, dents, or scratches in the mating surfaces

62. Gasket Rules Inspect for leaks before disassembly
Be careful not to damage mating surfaces while removing parts
Clean off old gaskets carefully
Wash and dry parts thoroughly
Compare the new gasket to the shape of the mating surface

63. Gasket Rules Use a sealer if specified
When assembling, start all bolts by hand
Tighten fasteners in steps
Use a crisscross tightening pattern
Do not overtighten fasteners
apply only the specified torque

64. Sealers
Gaskets are often coated with a sealer to help prevent leakage and to hold the gasket in place during assembly

65. Types of Sealers

66. Form-in-Place Gaskets
Used instead of conventional fiber or rubber gaskets
Two common types are:
room temperature vulcanizing (RTV) sealer
anaerobic sealer

67. RTV Sealer Also called silicone sealer Dries in contact with air
Used to form a rubber-like gasket on thin, flexible flanges
Available in tubes
has a shelf life of one to two years

68. Commonly recommended where two different gaskets join
RTV Sealer
Commonly recommended where two different gaskets join

69. Using RTV Sealer
Apply in a continuous bead that is approximately 1/8” (3 mm) wide
Circle all mounting holes
Torque components in place while the RTV is still wet to the touch
within about 10 minutes of application

70. Anaerobic Sealer
Cures to a plastic-like substance in the absence of air
Designed for tightly fitting, thick parts
Used between two smooth, true surfaces

71. Using Anaerobic Sealer
Apply in a continuous bead that is approximately 1/16"–3/32" (1.5 mm– 2 mm) wide
Circle all mounting holes
Torque components in place within 15 minutes of sealer application

72. Both anaerobic and RTV sealers are used on this water pump
Using Sealers
Both anaerobic and RTV sealers are used on this water pump

73. Seals Prevent leakage between a stationary part and a moving part
Found in engines, transmissions, power steering units, and any part containing fluid and moving parts
Made of synthetic rubber molded onto a metal body

74. Seal lip faces the fluid and keeps it inside the part
Seal Application
Seal lip faces the fluid and keeps it inside the part

75. Seal Rules Inspect the seal for leakage before disassembly
if the seal is leaking, look for a bent shaft, misaligned seal housing, or damaged parts
Remove the old seal carefully, without scratching the seal housing

76. Inspect shafts for wear and burrs
Seal Rules
Inspect shafts for wear and burrs

77. Seal Rules Compare the old seal to the new seal
make sure the inner and outer diameters match before installation
Install the new seal correctly
coat the outside with an approved sealer
coat the inner lip of the seal with system fluid
install the seal with the sealing lip toward the inside of the part

78. O-Ring Seal Stationary seal that fits into a groove between two parts
When the parts are assembled, the synthetic rubber seal is partially compressed to form a leakproof joint

79. O-Ring Seal
Normally, the O-ring seal is coated with system fluid before installation

80. Specially-shaped seal that fits down into a groove formed in the part
Synthetic Seal
Specially-shaped seal that fits down into a groove formed in the part