11 Threaded Fasteners_1.ppt
Transcript of 11 Threaded Fasteners_1.ppt
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Chapter 11 ThreadedFasteners
• Two Basic types of fasteners: Permanent & removable
• Permanent- Examples: ivets & welds
• emovable- Examples: bolts! screws! n"ts! pins! rin#s $eys
• %tandardiation red"ces the costs of fasteners
• ' p"rposes – To hold parts to#ether
– To ad("st
– To transfer power
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%crew Threads
• )e*nition: a %CE+ T,E) is a rid#e of "niform sectionin the form of a helix on the external or internal s"rface of acylinder
• )e*nition: the P.TC, of a thread P is the distance from a
point on the thread form to the correspondin# point on thenext form! meas"red parallel to the axis
• )e*nition: the /E) / is the distance the threaded partwo"ld move parallel to the axis d"rin# one completerotation in relation to a *xed matin# part 0the distance a
screw wo"ld enter a threaded hole in one t"rn
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THREADED FASTENERS
%CE+ T,E) TE2%
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THREADED FASTENERS
T,E) F32%
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THREADED FASTENERS
T,E) F32%
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Three types of threadrepresentation "sed on
wor$in# drawin#s• %impli*ed
• )etailed
•
%chematic
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i#ht- and /eft-,and threads
• Threads are ass"med to be ri#hthand "nless otherwise desi#nated
• bolt bein# threaded into a tappedhole wo"ld be t"rned in a ri#ht-hand0cloc$wise direction
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THREADED FASTENERS
.4,T- 5) /EFT-,5) T,E)%
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THREADED FASTENERS
%.54/E T,E)
/E) 6 1P
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THREADED FASTENERS
)37B/E T,E)
/E) 6 8P
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THREADED FASTENERS
T.P/E T,E)
/E) 6 'P
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.nch Threads
• )e*nition: P.TC, 619threads per inch
• )e*nition: T,E) %E.E% are forfasteners with di;erent diameters and
the same threads per inch
• 75C 7ni*ed Co"rse Thread %eries
• 75F 7ni*ed Fine Thread %eries 0Table
appendix
• 75EF extra *ne thread series
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THREADED FASTENERS
B%.C T,E) C//37T
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Thread Class1!8!' External1B!8B!'B .nternal
• 1!1B: loosest *t
• 8!8B: ordinary #ood #rade ofcommercial prod"ct
• '!'B: ,i#h-#rade commercial prod"cts
• Example: <=>?-1? 75C-8 class of *t• 5ominal )iameter thread series
threads9inch0)iameter! threads9inch! thread form & series!
class of *t
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THREADED FASTENERS
E@TE5/ T,E)%
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THREADED FASTENERS
B/.5) ,3/E .5TE5/ T,E)
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2etric Threads• )e*nition: Pitch for metric threads is the distance between
correspondin# points on ad(acent teeth<• Co"rse-thread is intended for #eneral en#ineerin# wor$ and
commercial applications
• Fine-thread series is for #eneral "se< Compared with coarse! a*ne-thread screw is stron#er in both tensile and torsional stren#th
• )e*nition: the F.T of a screw thread is the amo"nt of clearancebetween the internal and external threads when they areassembled
• Tolerance #rades: the lar#er the n"mber! the lar#er the tolerance
– Tolerance position e 0lar#e allowance
– Tolerance position # 0small allowance
–
Tolerance position h 0no allowance – For internal threads:
• Tolerance position 4 0small allowance
• Tolerance position , 0no allowance
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THREADED FASTENERS
B%.C T,E) C//37T
2ET.C T,E)%
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.%3 2etric %crew Thread)esi#nation
• 5ominal sie 0basic ma(or diameterand pitch expressed in millimeters<
• Example: 21A x 1<> >#A#
2etric desi#nation 5ominal diameter Pitch Tolerance position &
#rade
• Example: 21? x 1<> x 8>
1?mm 1<> pitch 8> mm lon#
• Example: 21A 0pitch may be omitted for coarse threads
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2etric Threads contin"ed
• For external threads! the len#th of the threadmay be #iven as a dimension of the drawin#<
• For threaded holes that #o all the waythro"#h the part! the term T,7 issometimes added
• .f no depth is #iven! the hole is ass"med to#o T,7
•
For threaded holes that do not #o all the waythr"! the depth is #iven in a note 0minim"mdepth of f"ll thread Ex< 218 x 1<=> x 8?
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Pipe Threads
• .nch: D-5PT or D 5PT
• 2etric: D .5< 5PT or D .5<-5PT
•
5ominal diameter and pipe thic$nessspecify inch-sied pipe 0typical• D6nominal diameter
• 6n"mber of threads9inch
•
56merican %tandard• P6pipe
• %6strai#ht pipe thread
• T6taper pipe thread