1. Fasteners and Sealants

2. Fasteners
Question: What is the most important yet typically taken for granted component of an internal combustion engine? Answer: Fasteners If one little rod bolt fails you can general kiss the bottom end goodbye. If a cylinder head does not get the proper clamping force from a fastener, the head gasket is sure to blow.

3. Fasteners are devices that hold the parts of a car together
Fasteners are devices that hold the parts of a car together. There are thousands of fasteners that hold a vehicle together.
Bolts: A bolt is a 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.

4. Every bolt behaves like a spring
Every bolt behaves like a spring. If we apply a tensile (a metal's resistance to being pulled apart) pre-load to the bolt it will elongate (stretch). Also present within the bolt is a force waiting to return the bolt to its original length.
It is this property of the bolt trying to return to its original length that gives the fastener its holding ability.
As long as the bolt's pre-load is within the elastic range of the stress/strain, permanent deformation of the bolt will not result.

5. Bolt and Nut terminology:
Bolts and nuts come in various sizes, grades, strengths, and thread types. It is important to be familiar with these different bolt dimensions.
Bolt size – the measurement of the outside diameter of the bolt threads.
Bolt head size- the distance across the flats or the outer sides of the bolt head (same as wrench size)
Bolt length – measured from the bottom of the bolt head to the thread end of the bolt.
Thread pitch- Is the number of threads per inch. With metric fastener it’s the distance between each thread in millimeters.

7. Thread types:
Course threads UNC- unified national course
Fine threads UNF- unified national fine
Metric threads SI (international standard)
Thread pitch gauge

8. Threads
TPI stands for Threads Per Inch. This is simply a count of the number of threads per inch measured along the length of a fastener. TPI is used only with American fasteners.

9. Thread Pitch
Metric fasteners are specified with a thread pitch instead of a thread count. The thread pitch is the distance between threads expressed in millimeters (measured along the length of the fastener).
For example a thread pitch of 1.5 means that the distance between one thread and the next is 1.5mm.

10. Bolt Grade
Tensile strength or grade, refers to the amount of pull a fastener can withstand before breaking.
Bolts are made of different metals, some stronger than others. Tensile strength can vary from bolt to bolt.
US customary bolts are marked with slash marks on the head of the bolt .
Metric bolts are given a number for example 8.8 or 10.9 the larger the number the stronger the bolt.

12. Bolt Description Imperial
¾ - 10 UNC- 2A X 1 3/4
¾ - Thread diameter or bolt size
10 – Threads per inch
UNC – Unified coarse
2A – Fit symbol
1 ¾ - Bolt Length

13. Bolt Description Metric
M – 20 X 2.00 X 50 – 8.8
M-20 – Metric thread/ diameter of threads in mm (bolt size)
Distance between threads (pitch)
50- Length in mm
8.8 – Strength (grade)

14. Nut Types
There are many types of nuts used in a vehicle. These are some of the most common ones used in the automotive manufacturing sector.

15. Castle Nuts & Nylon Nuts
A cotter pin slides through a castle nut and a hole in the bolt. This makes sure the nut cannot turn and come off. Nylon nut uses a plastic ring placed at the end of the nut to act like a stop. These two styles of nuts are often used in the automotive industry.

16. Washers
Washers are used under bolt heads and nuts. The two basic types are flat washers and lock washers.
Washer must be correctly sized to fit the shank of the bolt to prevent damage to the bolt's shank and be concave (dish) resistant. If the washer is too soft, the washer will concave and fail to provide a uniformed load transfer
Washers that are too hard could fracture and fall out of position, releasing the bolt's pre-load.

17. Flat washer
Increases the clamping surface under the fastener and it prevents the bolt or nut from digging into a part.

18. Lock washer
Prevents the bolt or nut from becoming loose under stress and vibration.
Lock washers are not to be used were high heat is present or they loose their locking memory. These are split lock washer and a toothed lock washer

19. Machine screws
Are similar to bolts, but they normally have screw type heads. They are threaded along their full length and are relatively small.
Machine screws are used to secure parts when clamping loads are light. They come in various head shapes.

20. Snap Rings
A snap ring fits into a groove in a part and commonly holds shafts, bearings, gears, pins, and other similar components in place. Snap ring pliers are needed to remove and install snap rings.
The snap rings shown are internal type, external type, and external “E”-type

21. Keys
A metal key fits into a key seat, or slot, cut into a shaft and a key way cut into the mating part, such as a gear, pulley, or collar. The key prevents the part from turning on its shaft.

22. Set Screws
Are normally used to lock a part onto a shaft. They can be used with or without keyways.
A set screw is a headless fastener normally designed to accept a hex (Allen) wrench or screwdriver

23. Torquing Bolts and Nuts
It is very important that bolts and nuts are tightened properly. This is called torquing.
If over tightened, a bolt will stretch and possible break. The threads could also fail.
If under tightened the bolt may loosen and fall out. Part movement could also shear the fastener or break a gasket, causing leakage.

24. Torque specifications
Tightening values are given by the auto manufacturer so technicians can tighten the fasteners to their stretching limits without compromising the integrity of the fastener. Torque specifications are given for all precision assemblies, such as engines, transmissions, and differentials.
Service manuals sometimes recommend new bolts because of torque to yield process (Head bolts).

25. Torque to Yield
Bolt tightening methods requires a specific bolt torque, followed by turning the bolt a specific number of degrees.
After using a torque wrench, a degree wheel adapter is placed between the wrench and the socket. The fastener is then turned until the degree wheel reads as specified by the manufacturer.
This stretches the bolt to its correct yield point and preloads the fastener for better clamping under varying conditions.

26. Torque Stretch
Determined by measuring bolt length change while torquing the bolt.
Example; measuring connecting rod bolts before and after tightening using a gauge.
Too much stretch indicates bolt weakness. Not enough stretch may indicate thread problems affecting torque.

27. Using a Torque Wrench Keep a steady pull on the wrench
Clean the fasteners threads
Avoid using universal joints
Read a torque wrench looking straight down at the tool
Only use a general torque scale when the manufactures specifications are not available
Pull only on the handle of the wrench
Tighten the bolts in a step torque
Retorque when required by the manufacture. Example cylinder heads, and exhaust manifolds.

28. General Torque Specs

29. Extracting Broken Fastener
A technician must be able to remove broken bolts, screws, studs and fasteners that have rounded-off heads.
Locking pliers - used for badly rusted heads and rounded off fasteners.
Stud puller-can remove studs and broken bolts that have been broken off at the surface of the part.

30. Other Methods
If fasteners are too short to grasp with a tool there are a variety of methods to use;
Hammer and punch – Angle the punch on the fastener so the blows from the hammer will walk out the bolt.
Hacksaw and Flat screwdriver- Cut a channel into the broken fastener then use the screwdriver to turn the fastener out
Weld a bolt onto the broken fastener

31. “Easy out” screw extractor – Drill a hole into the center of the broken fastener. Then, lightly tap the correct size extractor into the hole. Then, unscrew the broken bolt by simple turning the extractor with a wrench.
Note: DON’T BREAK THE EXTRACTOR OFF

32. Rust Penetrate
It is a chemical that dissolves rust or corrosion. It is often applied to rusted fasteners to aid in their removal.
Allow the penetrate to soak for a few minutes. This will help the fastener to free up without breakage.

33. Gaskets & Seals
Gaskets and seals are used between parts to prevent leakage of engine oil, coolant, transmission oil, and other fluids.
Gasket: Is a soft, flexible material. It can be made of fiber materials, rubber, neoprene, cork, treated paper, or thin steel.
When the parts are fastened tightly together the gasket is compressed and deformed.
This fills in small gaps or imperfections in the surfaces and a leak proof seal is created.

34. Gasket Rules Inspect for leaks before disassemble.
Be careful not to nick, gouge, or dent mating surfaces while removing parts.
Clean off old gaskets carefully.
Wash and dry parts thoroughly using solvent. Then wipe the surface clean.
Compare the new gasket to the surface of the part to make sure everything will line up (bolt holes, cut outs).
Use sealer if needed. Use sealer sparingly!
Tighten the fastener in steps. When more then one fastener is used to retain the part don’t over tighten.

35. Sealers
They help prevent leakage and hold the gasket in place during assembly.
There are numerous sealers with different uses:
Hardening sealers - used on permanent assemblies, such as threads and fittings. They are usually heat and chemical resistant.
Non-hardening sealers - used on assemblies that are to be removed, such as plates, covers, flanges.

36. Form –in- Place Gaskets
Are special sealers used instead of conventional fiber or rubber gaskets. The two types are:
R.T.V (room temperature vulcanizing)- comes in a tube and is used to make a rubber like gasket that dries when it comes in contact with air.
Anaerobic sealer - cures to a plastic like substance in the absence of air. It is used on thick parts and the surface must be smooth, true and not flexible.

38. Lets make a gasket