Transcript T-DAP MAP 32 - Centennial College

T-DAP MAP 32
WPP-Fasteners & Hardware
Agenda
Fastener terminology & application
 Metric, Imperial and non-standard
hardware
 Physical properties of hardware
 Factors that affect torque
 Fastener chemicals
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Fasteners & hardware
Function: To hold things together
 Most common automotive type –
threaded fastener
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Fasteners & hardware
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Automotive hardware includes:
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bolts / nuts
screws
studs
locking devices
pins
rivets
keys
washers
retaining rings
helicoils
Fasteners & hardware
Threaded fasteners are available in
many sizes, designs & threads
 Threads can be rolled - definition
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“Threads formed by tightly pressing or
rolling the piece of stock between serrated
dies. This is the most common method of
creating threaded fasteners today.”
Rolled threads = 30% stronger and
better fatigue resistance
Fasteners & hardware
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Threads can be cut - definition
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“Threads formed by cutting into a piece of
stock.”
Fasteners & hardware
Fasteners & hardware
Fasteners & hardware
Fasteners & hardware
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Fasteners are made to imperial or
metric measurements
4 classifications of threads (imperial)
1.
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3.
4.
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Unified National Coarse (UNC)
Unified National Fine (UNF)
Unified National Extra fine (UNEF)
Unified National Pipe Thread (NPT,UNPT)
Metric fasteners available in standard,
fine and superfine
Fasteners & hardware
Cap screws (a.k.a. bolts) nomenclature
 S = shank diameter
 T = thread diameter
 R = root diameter
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Fasteners & hardware
When measuring fastener diameter,
always use “T” thread diameter which
measures at the crest of the thread
 Beware: hex head size is not bolt size
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Fasteners & hardware
Fasteners & hardware
When measuring fastener diameter,
always use “T” thread diameter which
measures at the crest of the thread
 Beware: hex head size is not bolt size
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Fasteners & hardware
Bolts are usually made from steel
 Different grades of steel give different
strengths
 Property Class
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Imperial bolts (fractional) have lines in the
head of the bolt
 Metric bolts have decimal number in the
head of the bolt
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Fasteners & hardware
Fasteners & hardware
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Head markings other than property class
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Manufacturer specific (warranty purposes)
Fasteners & hardware
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Approximate yields strengths
Imperial
Metric
Max pound
force per
square inch
Grade 1 Grade 5
4.5
8.8
60,000 120,000
Grade 7 Grade 8
9.8
10.9
130,000 150,000
Fasteners & hardware
Property class explained
 Metric bolts – numerical e.g. 10.9
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10 represents the grade or tensile strength
 9 represents the yield point as a percentage
of tensile strength
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10 = 145,000 lbs/inch tensile strength
 9 = 130,500 lbs/inch yield strength
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Fasteners & hardware
Understanding bolt strength
 Tensile strength
 Yield strength
 Shear strength
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Fasteners & hardware
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Tensile strength (grade)
Sometimes called ultimate strength, is the
maximum stress level a material can
withstand without breaking
 Under how much pressure will the fastener
break
 Factors
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Materials
 Diameter of bolt
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Accelerators?
Fasteners & hardware
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Yield strength
Maximum strength a material can withstand
and return to its original form without
damage or deformation
 Identifying a bolt that has reached yield
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Fasteners & hardware
Fasteners & hardware
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Shear strength
The force required to shear or split the bolt
into two parts
 Approx 60% of ultimate tension strength
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Fasteners & hardware
Fasteners & hardware
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M8 X 1.5 X 24
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M = metric
8=?
1.5 = ?
24 = ?
½ X 13 X 1
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Imperial
½=?
13 = ?
1=?
Fasteners & hardware
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Studs
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Rods with threads on both ends
Can have different threads on each end
Why a stud/nut vs. a bolt?
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Soft material where coarse threads are needed
but requires clamping force of fine threads
Remember the finer the thread the greater
holding power & resistance to vibration
Remember coarse threads for soft material
Square, cross, circle
Fasteners & hardware
Fasteners & hardware
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Nuts
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Most common is hex nut
Grade (tensile strength only) of nut must
match bolt grade
If a grade 8 bolt were used with a grade 5
nut – connection is max grade 5
Fasteners & hardware
Fasteners & hardware
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Types of nuts
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Hex nut
Hex nut – nylon insert (lock nut)
Hex jam nylon lock nuts
Cap nuts
Flanged serrated
Wing nuts
K-nuts
Prevailing torque lock nuts
Castellated
Fasteners & hardware
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Washers
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Different washers have defined purposes
Flat washers
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spread load of tightening nut or bolt
prevents digging
Copper – sealing – crush
Lock washers
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Lock head of bolt or nut to prevent loosening
Fasteners & hardware
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Types of washers available in metric &
imperial
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Flat
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USS
SAE
Fender
Lock washers
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Split
Internal teeth
External teeth
Fasteners & hardware
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Pins
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Push pins
Cotter pins
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Bend once
One time use only! Throw away!
Use with castellated nuts/shafts
Available in different sizes and lengths
Fasteners & hardware
Fasteners & hardware
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Rivets
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Used for attaching two pieces of material
Rivet gun
Rivets
Fasteners & hardware
Fasteners & hardware
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Keys
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Used for aligning shafts
Used for preventing pulley rotation on
shaft
Key sits in keyway machined into
respective parts
Types
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Flat/squre
woodruff
Fasteners & hardware
Fasteners & hardware
Fasteners & hardware
Fasteners & hardware
Fasteners & hardware
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Retaining rings and snap rings are
fasteners used to axially position a
component on a shaft or in a bore. The
primary retaining ring type can be
internal or external. Internal retaining
rings fit into a housing or bore.
Note diameter and thickness of
fastener for proper application
Fasteners & hardware
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Use special pliers for retaining ring
installation and removal
Under tension – watch for launched
rings
Fasteners & hardware
Fasteners & hardware
Fasteners & hardware
Fasteners & hardware
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Thread repair
Tap/die set
Helicoil ™
Fasteners & hardware
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Helicoil insert are made from high quality
stainless steel wire, with a diamond shaped
cross section, wound to the shape of a
spring thread. The insert, which is larger in
diameter than the tapped hole, is
compressed during installation then allowed
to spring back, permanently anchoring the
insert in the tapped hole. Because of its
larger diameter, the Helicoil Insert has a
greater contact area and is normally stronger
than the original threads. (toolsnextday UK)
Fasteners & hardware
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Step 1 – Drill to clear out bad threads
**right size please
Step 2 – tap with helicoil tap
Step 3 – insert helicoil
Step 4 – knock tab *if in combustion
chamber break off and pull out with
pliers
Fasteners & hardware
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Step 1
Fasteners & hardware
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Step 2
Fasteners & hardware
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Step 3
Fasteners & hardware
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Step 4
Fasteners & hardware
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OEMs may recommend the use of sealant or
lubricant per application
Antiseize
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Thread sealants
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May recommend in aluminum
Used on fasteners tightened in oil cavities or
coolant passages
Threadlocker
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Prevents bolts from loosening due to vibration
Fasteners & hardware
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Major manufacturer in
sealants/lubricants/threadlockers is
Loctite
Fasteners & hardware
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Factors that affect torque
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Thread condition
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Lubrication
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Reduces friction (even water) – changes torque value
Temperature
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Damaged/Burred
Corrosion
Heat vs. cold – shrinkage vs. expansion
Fastener composition
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Different materials have different torque values
Fasteners & hardware
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Factors that affect torque
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What do you do?
Always follow manufacturer literature on
fastener torque
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Apply lubrication when specified otherwise dry
*wheel nuts
Torque Chart
Fasteners & hardware