2-1 2-1 Fasteners and FasteningFasteners and Fastening2-22-2 Threaded FastenersThreaded Fasteners2-32-3 Screw and Screw Thread Screw and Screw Thread 2-42-4 Screw Thread TerminologyScrew Thread Terminology2-52-5 Basic Profiles of Screw ThreadsBasic Profiles of Screw Threads2-62-6 Types of V-threadsTypes of V-threads2-72-7 Profile of Square Thread and its Profile of Square Thread and its modificationsmodifications2-82-8 Right-Hand and Left-Hand ThreadsRight-Hand and Left-Hand Threads2-92-9 Single-start and Multi-start ThreadsSingle-start and Multi-start Threads2-102-10 Bolts and NutsBolts and Nuts2-112-11 Chamfering of Bolts and NutsChamfering of Bolts and Nuts2-122-12 Washer facing of the hexagonal bolts and Washer facing of the hexagonal bolts and nutsnuts2-132-13 Counter-sinking of the nutCounter-sinking of the nut2-142-14 Method of drawing hexagonal head bolt Method of drawing hexagonal head bolt and nutand nut2-152-15 Method of drawing a square head bolt and Method of drawing a square head bolt and nutnut

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A mechanical element which holds two or more parts of a

machine or a structure is known as fastener. The process is

called fastening.

Permanent fastening: it involves destruction during

separation

press fits

shrink fits

rivets

welding, brazing, and soldering

adhesives

Temporary fastening: it doesn’t involve destruction

during separation

Bolts and nuts

studs and nuts

screws

keys

pins, etc…

Externally threaded fasteners

Internally threaded fasteners

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Use:

to fasten parts together

for the relative adjustment of the adjacent parts

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To transmit motion and

power

Lead=L=n pn = number of start

Figure 2-1Terminology of screw threads. Sharp Vee Threads shown for clarity; the crests and roots are actually flattened or rounded during the forming operation

V-thread

Square thread

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Right-hand thread – A screw thread that is screwed in by rotating CW.

Left-hand thread – A screw thread that is screwed in by rotating CCW.

(a) Single (STANDARD) (b) double (c) triple threaded

2-102-10 Bolts and NutsBolts and Nuts

Bolt . Threaded fastener designed topass through holes in mating members and to be secured by tightening a nut from the end opposite the head of the bolt.

2-112-11 Chamfering of Bolts and Chamfering of Bolts and NutsNuts

2-112-11 Chamfering of Bolts and Chamfering of Bolts and NutsNuts

2-122-12 Washer facing of the hexagonal Washer facing of the hexagonal bolts and nutsbolts and nuts

The difference between a finished andUnfinished hex head bolt is a washerUnder the head of the finished bolt.

Finished vs.Unfinished Bolts:

2-132-13 Counter-sinking of the nutCounter-sinking of the nut

Countersinking of nut facilitates the gripping of the bolt end when the nut first enters while it is threaded on

2-142-14 Method of drawing Method of drawing hexagonal head bolt and nuthexagonal head bolt and nut

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2-142-14 Method of drawing Method of drawing hexagonal head bolt and nuthexagonal head bolt and nut

2-142-14 Method of drawing Method of drawing hexagonal head bolt and nuthexagonal head bolt and nut

2-142-14 Method of drawing Method of drawing hexagonal head bolt and nuthexagonal head bolt and nut

2-152-15 Method of drawing a square Method of drawing a square head bolt and nuthead bolt and nut

2-152-15 Method of drawing a square Method of drawing a square head bolt and nuthead bolt and nut

2-152-15 Method of drawing a square Method of drawing a square head bolt and nuthead bolt and nut

Conventional representati

ons of threads

2.17.Locking of nuts

2.21 Foundation bolts