bolting & riveting
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Bolted joints are one of the most commonelements in construction and machine
design. They consist of fasteners that capture and
join other parts, and are secured with themating of screw threads.
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Screws engage the
threads of nuts or ofother parts.
A nut is a threadedfastening with internalthread. It is screwed on
the bolt and is of a shape
designed to be grippedby a wrench or by hand.
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Thread Terminology
Crest–
Peak edge of thread Root – Bottom of thread cut into a cylindrical
body
Thread angle – Angle between threads faces
External Thread
CrestCrestRootRoot
Thread angleThread angle
Internal Thread
CrestCrestRootRoot
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Thread Terminology
Major diameter – Largest diameter on anexternal or internal thread
Minor diameter – Smallest diameter on an
external or internal thread
Internal ThreadExternal Thread
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M a j o r d i a .
M a j o r d i a .
M a j o r d i a .
M i n o r d
i a .
M i n o r d
i a .
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i a .
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Thread Terminology
Pitch – Distance between crests of threads
Internal ThreadExternal Thread
PitchPitch
PitchPitch
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The act of tightening a bolt engages several different types of mechanical
force that help the resultant joint remain secure. The main forcesgenerated by bolt installation include:
Clamping Force: This is a type of compression that the bolt applies to the
joint, holding the two components together.
Preloading Force: Turning the bolt causes the threads to engage andstretch, which produces the preload force that keeps the threads in place.
Shear Force: The shear force is the transverse pressure working against
the bolt in a perpendicular direction. It can be present alone or incombination with tension force.
Tension Force: Tension force applies to the length of the bolt, providingpressure along its vertical dimension, rather than its width.
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A rivet is a permanent mechanical fastener
They are pre-shaped at one end and have theirother end reshaped when they are put to use.All have a smooth shaft that passes throughthe materials being bonded. They are used to
join two or more materials together.
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• The end opposite the head is called the buck-tail .• On installation the rivet is placed in a punched or
drilled hole, and the tail is upset, or bucked (i.e.,
deformed)
• It expands to about 1.5 times the original shaft
diameter, holding the rivet in place.
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Rivets have been used to make watertighthulls on ships, high-pressure tanks for steamboilers and refineries, gussets for bridges,airtight skins on airplanes --- even used tobind heavy fabrics like denim that could not be
easily sewn.
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