t-dap map 32 wpp-fasteners & hardware. agenda fastener terminology & application metric,...

T-DAP MAP 32

WPP-Fasteners & Hardware

Agenda

Fastener terminology & applicationMetric, Imperial and non-standard

hardwarePhysical properties of hardwareFactors that affect torqueFastener chemicals

Fasteners & hardware

Function: To hold things togetherMost common automotive type –

threaded fastener


Automotive hardware includes: bolts / nuts screws studs locking devices pins rivets keys washers retaining rings helicoils


Threaded fasteners are available in many sizes, designs & threads

Threads can be rolled - definition “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


Threads can be cut - definition “Threads formed by cutting into a piece of

stock.”


Fasteners are made to imperial or metric measurements

4 classifications of threads (imperial)1. Unified National Coarse (UNC)2. Unified National Fine (UNF)3. Unified National Extra fine (UNEF)4. Unified National Pipe Thread (NPT,UNPT)

Metric fasteners available in standard, fine and superfine


Cap screws (a.k.a. bolts) nomenclatureS = shank diameterT = thread diameterR = root diameter


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


Bolts are usually made from steelDifferent grades of steel give different

strengthsProperty Class

Imperial bolts (fractional) have lines in the head of the bolt

Metric bolts have decimal number in the head of the bolt


Head markings other than property classManufacturer specific (warranty purposes)


Approximate yields strengths

Grade 1 Grade 5 Grade 7 Grade 8

4.5 8.8 9.8 10.9

60,000 120,000 130,000 150,000

Imperial

Metric

Max pound force per

square inch


Property class explainedMetric bolts – numerical e.g. 10.9

10 represents the grade or tensile strength9 represents the yield point as a percentage

of tensile strength 10 = 145,000 lbs/inch tensile strength9 = 130,500 lbs/inch yield strength


Understanding bolt strengthTensile strength Yield strengthShear strength


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

FactorsMaterialsDiameter of bolt

Accelerators?


Yield strengthMaximum strength a material can withstand

and return to its original form without damage or deformation

Identifying a bolt that has reached yield


Shear strengthThe force required to shear or split the bolt

into two parts Approx 60% of ultimate tension strength


M8 X 1.5 X 24 M = metric 8 = ? 1.5 = ? 24 = ?

½ X 13 X 1 Imperial ½ = ? 13 = ? 1 = ?


Studs Rods with threads on both ends Can have different threads on each end Why a stud/nut vs. a bolt?

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


Nuts 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


Types of nuts 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


Washers Different washers have defined purposes Flat washers

spread load of tightening nut or bolt prevents digging Copper – sealing – crush

Lock washers Lock head of bolt or nut to prevent loosening


Types of washers available in metric & imperial

Flat USS SAE Fender

Lock washers Split Internal teeth External teeth


Pins Push pins Cotter pins

Bend once One time use only! Throw away! Use with castellated nuts/shafts Available in different sizes and lengths


Rivets Used for attaching two pieces of material Rivet gun Rivets


Keys Used for aligning shafts Used for preventing pulley rotation on

shaft Key sits in keyway machined into

respective parts Types

Flat/squre woodruff


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


Use special pliers for retaining ring installation and removal

Under tension – watch for launched rings


Thread repair Tap/die set Helicoil ™


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)


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


Step 1


Step 2


Step 3


Step 4


OEMs may recommend the use of sealant or lubricant per application

Antiseize May recommend in aluminum

Thread sealants Used on fasteners tightened in oil cavities or

coolant passages

Threadlocker Prevents bolts from loosening due to vibration


Major manufacturer in sealants/lubricants/threadlockers is Loctite


Factors that affect torque Thread condition

Damaged/Burred Corrosion

Lubrication Reduces friction (even water) – changes torque value

Temperature Heat vs. cold – shrinkage vs. expansion

Fastener composition Different materials have different torque values


Factors that affect torque What do you do? Always follow manufacturer literature on

fastener torque Apply lubrication when specified otherwise dry *wheel nuts

Torque Chart

t-dap map 32 wpp-fasteners & hardware. agenda fastener terminology & application metric,...

Documents

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