FASTENERS,GASKETS,
SEALS AND SEALANTS.
Produced By
Joe Wintermute
ASE Certified
Master Automobile Technician
FASTENERS
• Fasteners are devices that hold the parts
of a car together.
• Thousands of fasteners are used in the
modern automobile.
• The next slide shows how the fasteners
could be used (look familiar)
NUTS AND BOLTS.
• A bolt is a metal rod with external threads
(outside) on one end and a head on the
other.
• When a bolt is threaded into a part without
a nut it is called a cap screw.
• A nut has internal threads (inside) and
usually a hex(6 sided) outer shape
• When a nut is screwed onto a bolt a
powerful clamping force is produced.
IN AUTOMOTIVE TECHNOLOGY
• Nuts and bolts are named after the parts
they hold. For example “head bolts” these
bolts obviously hold the cylinder head to
the engine block.
• Can you tell me what the bolts that
connect the piston ROD to the crankshaft
are called?
• That’s correct they are called ROD bolts.
NUT AND BOLT
TERMINOLOGY.
• Nuts and bolts come in a wide variety of
sizes and grades (strength) and thread
types.
• It is important to understand the
differences.
• The most important bolt dimensions are.
• Bolt size, bolt size is the measurement of
the outside diameter of the bolt threads.
TERMINOLOGY CON’T
• Bolt head size, is the distance across the flats or
outer sides of a bolt head
• IT IS THE SAME AS THE WRENCH SIZE!
• Bolt length, is measured from the bottom of the
bolt head to the threaded end of the bolt.
• Thread pitch, is the distance between the
threads of a bolt.
• With U.S. fasteners it is the number of threads
per inch.
• With metric fasteners it is the distance between
the threads in millimeters.
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)
Never interchange thread types or
thread damage will result!
Different thread directions
• Bolts come in right hand thread of left hand
thread.
• No this does not mean that you have to use your
left hand to turn a left handed bolt.
• This simply means that one turns to the right to
tighten and one turns to the left to tighten.
• Left thread fasteners are identified with a capital
(L) on their heads
BOLT GRADES
• Bolt grading or tensile strength refers to
the amount of pull of stretch a fastener can
withstand before breaking.
• Tensile strengths can vary, bolts are made
of different metals some stronger than
others.
BOLT HEAD MARKINGS
• Also called grade markings specify the
tensile strength of a bolt.
• COVENTIONAL BOLTS, are marked with
lines or slash marks.
• The more lines the stronger the bolt.
• METRIC BOLTS, are marked with a
numbering system.
• Yes you guessed it the larger the number
the stronger the bolt.
BOLT MARKINGS EXAMPLES
DANGER! PELIGRO!
• NEVER REPLACE A HIGH GRADE BOLT
WITH A LOW GRADE BOLT.
• THE WEAKER BOLT COULD EASILY
SNAP CAUSING PART FAILURE AND A
VERY DANGERIOUS SITUTATION!
BOLT DESCRIPTION
• A bolt description is a series of numbers
and letters that describe a bolt.
• These numbers and letters are needed
when buying a new bolt.
• For example M-20x2.00x50-8.8
• This is a description for a metric bolt.
Bolt Description
• The M tells us that it is a metric thread bolt.
• The 20 tells us that what the diameter of the
threads in millimeters is.
• The 2.00 is the distance between the threads in
millimeters. (this is referred to as THREAD
PITCH)
• The 50 tells us the length of the bolt in
millimeters.
• Lastly the 8.8 tells us how strong the bolt is or
it’s tensile strength.
NUT TYPES
• Many types of nuts are used in the
automotive field.
• The most common are shown below
COTTER PINS AND
WASHERS
• First a cotter pin is a safety device
normally used in a slotted nut.
• It keeps the nut from turning and coming
off.
• Washers are used under bolt heads and
nuts.
• There are two basic types of washers Flat
and Lock.
WASHERS
• FLAT WASHERS, Increase the clamping force of
a bolt or nut.
• LOCK WASHERS, Prevent the bolt or nut from
coming loose under stress and vibration.
• LOCK TABS OR PLATES, perform the same
function as flat washers and lock washers.
• They increase clamping surface area and
secure the fastener.
TORQUEING BOLTS.
• It is very important that nuts and bolts be
tightened properly.
• If OVERTIGHTENED, a bolt could stretch
and possibly break, the threads could also
fail.
• If UNDERTIGHTENED, a bolt could work
loose and fall out.
• Part movement could also shear the bolt in
two or break a gasket.
TORQUE SPECIFICATIONS
• Also called “TORQUE SPEC’S” are
tightening values given by an auto
manufacturer.
• They are normally given for all precision
assemblies.
• Such as CYLINDER HEAD TO BLOCK.
• TRANSMISSION TO ENGINE
USING A TORQUE WRENCH.
• When using a torque wrench follow these basic
rules.
• 1) Keep a steady pull on the wrench. For
accuracy do not use short jerky pull motions.
• 2) clean and lightly oil the fastener threads.
• 3) When possible avoid using swivel joints.
•
they can upset torque wrench accuracy.
• 4) When reading a beam type torque wrench
look straight down at the scale looking from an
angle can give a false reading.
TORQUE WRENCH.
• 5) A general torque reading chart should
only be used when manufacturer’s specs
are NOT available.
• 6) When manufacturer’s torque patterns
are not available, use a general crisscross
pattern.
• 7) pull only on the handle of a beam type
torque wrench do not let the beam touch
anything.
THERE IS A LOT TO KNOW ABOUT HOW
TO USE A TORQUE WRENCH
•
8) Retorque when required, on
some assemblies like cylinder heads,
intake manifolds and exhaust manifolds,
the bolts may have to be retightened after
reaching operating temperature.
THREAD REPAIRS
• A technician must be able to repair
damaged threads quickly and properly.
• Threaded holes can be damaged requiring
repairs.
MINOR THREAD REPAIRS
• Minor thread damage includes partial
flattening and other less serious problems.
• Minor thread damage can usually with a
thread chaser or threading tool.
MAJOR THREAD REPAIRS
• Major thread damage generally includes
• Badly smashed threads, striped threads
or threads that can not be repaired easily.
• Sometimes major thread damage is
repaired with either a tap or die.
TAPS
• A tap is a threaded tool.
• Used for cutting threads
into a hole.
• Various tap shapes are
provided.
• Some are used for
starting the threads
others for cutting threads
down to the bottom.
DIES
• A die cuts an external
thread
• It can be used to cut
threads on metal
rods.
• It can also be used to
cut threads on bolts,
shafts and pins.
TAP AND DIE RULES
• NEVER FORCE a tap handle or the tool could
break.
• For every one turn you must back off ¼ turn to
clean out the metal shavings.
• Keep taps and dies well oiled to ease the cutting
process and prolong tool life.
• Always use the correct size tap in a correctly
sized drilled hole.
• Use coarse threads when threading into soft
metal such as aluminum, coarse threads will
hold better than fine.
THREAD REPAIR INSERT
• A thread repair insert is a coil of metal that
when inserted into a hole will bring that
hole back to the manufacturers
specifications.
• They are used where an oversized hole
would be unacceptable.
• A good example of this would be a car that
is being restored original condition.
SHEET METAL SCREWS.
• Sheet metal screws are commonly used to
hold plastic and sheet metal parts.
• Sheet metal screws have tapering threads
that are widely spaced.
• Sheet metal screws come in a wide variety
of head shapes, sizes and screwdriver
head sizes.
NON THREADED FASTENERS.
• Numerous types of non threaded fasteners
are used in the assembly of an
automobile.
• It is important that you learn the most
common types.
SNAP RINGS
• A snap ring fits into a
groove in a part and
holds one part into
another.
• There are two types
of snap rings.
• INTERNAL and
EXTERNAL
KEYS AND KEYWAYS
• A metal key fits into a keyway (groove) cut
into a shaft and part.
• The key prevents the part from turning on
its shaft.
• SET SCREWS are used to lock a part
onto its shaft.
• They can be used with or without a
keyway.
SPLINES
• Splines are a series of slots cut into a
shaft and a mating part.
• Splines have one advantage over a key
splines allow the part to slide over the
shaft but still not rotate.
• This sliding lock system is commonly used
in transmissions and driveshafts.
ADHESIVES
• Adhesives (special glues) are widely used
on modern automobiles.
• They hold everything from emblems to
nuts and bolts together.
• Some are designed to stay soft and
pliable.
• Others dry hard some take hours to dry
while others take minutes.
GASKETS AND SEALS.
• Gaskets and seals are used between
parts to prevent leakage of various fluids.
• Such as engine oil, coolant, transmission
fluid and other fluids.
• It is important to understand a few
principles about gaskets and seals.
• If they are serviced improperly mechanical
failures can result!
GASKETS
• A gasket is a soft, flexible material placed
between two parts to prevent leakage.
• It can be made of many different materials such
as rubber, neoprene, cork, treated paper or thin
steel.
• When the parts are fastened together the gasket
is compressed and deformed.
• This forces the gasket to fill any imperfection in
the parts so there is no leakage.
GASKET RULES
• When working with gaskets remember the
following.
• Inspect for leaks before disassembly, if two parts
are leaking they should be inspected for defects
before reassembly.
• Avoid part damage during disassembly. Be
careful not to gouge, nick or scratch any
imperfection could cause a leak.
• Clean off old gasket carefully all of the old
material must be remove from the old parts.
Sealants
Sealants are commonly used with
gaskets to prevent leakage or to
hold the gasket in place.
Sealants
Type
Temperature
Range
Shellac
-65 to 350F
-54Cto 177C
Use
General assembly
Gaskets of paper,
felt,cardboard rubber
metal
Hardening
-65 to 400F
Gasket Sealant -54C to
205C
Permanent assemblies
Fittings threaded
connections and for
filling uneven surfaces
Non Harding
-65 to 400F
Gasket Sealant -54C to
205C
Semi permanent
assemblies cover
plates flanges
threaded assemblies
hose connections and
metal to metal
assemblies
Resistant
to
Gasoline,kersene
Two Types of Sealers
• Hardening sealers are used on permanent
assemblies such as fittings and threads.
• They are resistant to heat and most
chemicals.
• Non hardening sealers are used for semi
permanent assemblies such as cover
plates, flanges, threads, hose connectors
they are resistant to most chemicals.
Form in place Gaskets
• These are special sealers that are used
instead of gaskets.
• Two types of form in place gaskets are
RTV and anaerobic sealer.
• RTV (room temperature vulcanizing) is a
silicone based sealer that cures or dries in
the air in other words it needs the moisture
in the air to dry!