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Chapter 10Threads and Fasteners
TopicsExercises
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Summary
What will we learn in Chapter 10?→ How to represent fasteners and threads on
an engineering drawing.
→ How to calculate bolt and screw clearanceholes.
Key points→ Threads are represented by thread sy bols!
not by a realistic drawing.
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Threads and Fasteners
10.1) Fasteners
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Fasteners
Fasteners include→ bolts and nuts "threaded#→ set screws "threaded#
→ washers→ $eys→ pins
Fasteners are not a permanent meanso! assem"ly such as weldin# oradhesi$es.
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Fasteners
Fasteners and threaded !eatures must"e speci!ied on your en#ineerin#drawin#.
→ Threaded features% Threads are specified ina thread note.
→ &eneral 'asteners% Purchasing infor ationust be gi(en to allow the fastener to be
ordered correctly.
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Thread %e!initions
Screw Thread ) ridge of unifor sectionin the for of a heli*.
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Thread %e!initions
External Thread +*ternal threads are onthe outside of a e ber.
→ ) cha fer on the end of the screw threada$es it easier to engage the nut.
Cha fer
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Thread %e!initions
External Thread
→ )n e*ternal thread is cut using a die or alathe.
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Thread %e!initions
&nternal Thread ,nternal threads are onthe inside of a e ber.
→ )n internal thread is cut using a tap.
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Thread %e!initions
'a(or %& *%) The largest dia eter "'orboth internal and e*ternal threads#.
'inor %& *d) The s allest dia eter.
%epth o! thread "- d#/2
+itch %& *d + ) The dia eter at which a
line cuts the spaces and threads e ually.
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Thread %e!initions
Crest The top surface.
,oot The botto 1urface.
Side The surface between the crest androot.
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Thread %e!initions
+itch *+) The distance fro a point on ascrew thread to a corresponding point onthe ne*t thread "in/Threads#.
n#le o! Thread * ) The angle betweenthe threads.
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Thread %e!initions
Screw xis The longitudinal centerline.
-ead The distance a screw threadad(ances a*ially in one turn.
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Thread %e!initions
,i#ht anded Thread )d(ances whenturned C . "Threads are assu ed RHunless specified otherwise.#
-e!t anded Thread )d(ances whenturned CC .
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Types o! Thread
There are many di!!erent types o!thread !orms *shape) a$aila"le. Themost common are/
→ 3nified→ 4etric
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Types o! Thread
Thread !orm choice depends on/→ what it will be used for → length of engage ent
→ load→ etc5
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Types o! Thread *Form)
Thread ame Fi#ure ses
3nified screwthread
&eneral use.
,16 etricscrew thread
&eneral use.
1 uare ,deal threadfor powertrans ission.
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Types o! Thread *Form)
Thread ame Fi#ure ses
)C4+ 1tronger thans uare thread.
7uttress -esigned tohandle hea(y
forces in onedirection."Truc$ ac$#
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'anu!acturin# Threads
&nternal Threads→ 'irst a tap drill hole is cut with a twist drill.
The tap drill holeis a little biggerthan the inordia eter. hy9
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'anu!acturin# Threads
&nternal Threads→ Then the threads are cut using a tap.
The tap drill holeis longer than the
length of thethreads. hy9
,nco pletethreads
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'anu!acturin# Threads
&nternal Threads→ Cha fers are so eti es cut to allow for
easy engage ent.
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'anu!acturin# Threads
External Threads→ :ou start with a shaft the sa e si;e as the
a or dia eter.
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'anu!acturin# Threads
External Threads→ The threads are then cut using a die or on a
lathe.
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%rawin# Screw Threads
There are three methods o!representin# screw threads on adrawin#.
→ -etailed→ 1che atic→ 1i plified
1crew thread representation present inthis chapter is in accordance with the
S'E 213.456001 standard.
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%etailed ,epresentation
) detailed representation is a closeappro*i ation of the appearance of anactual screw thread.
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%etailed ,epresentation
Pros and Cons9 Pro%
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Schematic ,epresentation
The schematic representation usesstaggered lines to represent the threadroots and crests.
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Schematic ,epresentation
Pros and Cons9 Pro% =early as effecti(e as the detailedrepresentation and easier to draw.
Con% 1till ta$es so e ti e to draw.
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Schematic ,epresentation
,ules o! use !or Schematic threads→1hould not be used for hidden internal
threads or sections of e*ternal threads.
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Simpli!ied ,epresentation
The simplified representation uses (isibleand hidden lines to represent the a orand inor dia eters.
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Simpli!ied ,epresentation
Pros and Cons9Pro% 1i ple and fast to draw.Con% -oesn>t loo$ li$e a thread.
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Simpli!ied &nternal Threads
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Simpli!ied &nternal Threads
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%rawin# Screw Threads
Thread tables in the appendi* can beused to loo$ up (alue for the?→ Pitch
→ 4inor dia eter → Tap drill dia eter
,f screw thread tables are not a(ailable!the inor dia eter can be appro*i atedas @AB of the a or dia eter.
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ni!ied Threads *inch)
)fter drawing a thread! we need to identifythe si;e and thread for in a thread note.
Thread =ote
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ni!ied Thread ote Components
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ni!ied Threads *inch)
'a(or %iameter The largest dia eter.Threads per inch =u ber of threads perinch for a particular dia eter.
→ + ual to one o(er the pitch " /P#.
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ni!ied Threads *inch)
Thread Form and Series The shape ofthe thread cut.→ C D Unified National coarse .
E 'or general use.→ F D Unified National fine .E 3sed when high degree of tightness is re uired.
→ EF D Unified National extra fine .E 3sed when length of engage ent is li ited
"+*a ple% 1heet etal#.
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ni!ied Threads *inch)
Thread Class Closeness of fit betweenthe two ating threaded parts.→ 1 D &enerous tolerance. 'or rapid asse bly
and disasse bly.→ 6 D =or al production→ 7 D High accuracy
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ni!ied Threads *inch)
External or &nternal Threads→ D +*ternal threads→ 8 D ,nternal threads
,i#ht handed or le!t handed thread→ , D Right handed "right handed threads
are assu ed if not stated.#
→ - D
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ni!ied Threads *inch)
%epth o! thread The thread depth isgi(en at the end of the thread note andindicates the thread depth for internal
threads→ This is not the tap drill depth.
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ni!ied Threads *inch)
Thread class is assu ed to be 6.Threads are assu ed to be , .
4ay be left off if
assu ptions hold.
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ni!ied ational Thread Ta"les
Standard screw thread ta"les area$aila"le in order to loo9 up the→ 4a or dia eter
→ Threads per inch→ 4inor dia eter or Tap drill si;e.
Thread tables are located in )ppendi* 7.
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Exercise 1057
rite the thread note for a :10 !ine thread. "1ee )ppendi* 7#
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Exercise 1057
rite the thread note for a :10 !ine thread. "1ee )ppendi* 7#
0 F G2 3='
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Exercise 1057
rite the thread note for a :10 !ine thread. "1ee )ppendi* 7#→ ,s the a or dia eter 0 inches9 =o
0 F G2 3='
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Exercise 1057
rite the thread note for a :10 !ine thread. "1ee )ppendi* 7#→ ,s the a or dia eter 0 inches9 0. 0
0 F G2 3='
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Exercise 1057
rite the thread note for a :10 !ine thread. "1ee )ppendi* 7#→ hat is the inor dia eter9
0 F G2 3='
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Exercise 1057
rite the thread note for a :10 !ine thread. "1ee )ppendi* 7#→ hat is the inor dia eter9
0 F G2 3='D F .082A P D0. 0 F .082A/G2 D0.1;4
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'etric Threads
The etric thread note can contain a pitch diameter tolerance.
hat is the pitch dia eter9 s see.
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+itch %iameter
The pitch diameter cuts the threads at apoint where the distance of the spacese ual the distance of the threads.
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'etric Thread ote Components
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'etric Thread ote Components
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'etric Threads
'etric Form Placing an ' before thea or dia eter indicates the etric thread
for .
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'etric Threads
'a(or %iameter The largest dia eter +itch "P# 4illi eters per thread.
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'etric Threads
Tolerance Class ,t describes thelooseness or tightness of fit between theinternal and e*ternal threads.=u ber D Tolerance grade
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'etric Threads
Tolerance Class→ Tolerance &rade% 1 aller nu bers indicate
a tighter fit.→
Tolerance Position% 1pecifies the a ount ofallowance.E 3pper case letters D internal threadsE
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'etric Threads
Tolerance Class Two classes of etricthread fits are generally used.→ IH/Ig D &eneral purpose
→ IH/AgIg D Closer fit.→ ) tolerance class of IH/Ig is assu ed if it is
not specified.
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'etric Threads
,i#ht handed or -e!t handed thread→ , D Right handed "right handed threads
are assu ed if not stated.#→
- D
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'etric Threads
%epth o! thread ,t indicates the threaddepth for internal threads! not the tap drilldepth.
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'etric Thread ote
) tolerance class of 4
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'etric Thread Ta"les
Standard screw thread ta"les area$aila"le in order to loo9 up the/→ 4a or dia eter
→ Pitch→ Tap drill si;e or 4inor dia eter
Thread tables are located in )ppendi* 7.
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'ind this page.
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Exercise 105;
'or a n 14 internal etric thread.
+itch Tap drill %& 'inor %&"+*ternal#
2.A
JJ.A
G.IJ.2
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Exercise 105;
'or a n 14 internal etric thread.
hich has the finer thread9
→ Pitch D 2→ Pitch D .A
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Exercise 105;
rite the thread note for a 14 dia eter coarse thread.
4 I * 2
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%rawin# 8olts
% represents thea or dia eter.
=uts are drawn ina si ilar fashion.
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8olt and Screw Clearances
7olts and screwsattach oneaterial with a
clearance hole toanother aterialwith a threadedhole.
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Ta"le 1056 * ormal !it clearances)
6ther fits ay be found in )ppendi* 7.
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8olt and Screw Clearances
1o eti es bolt orscrew heads need tobe flush with thesurface. This can beachie(ed by usingeither a counter"ore or countersin9 depending on thefasteners head shape.
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8olt and Screw Clearances
Counter"oresCounterbores areholes designed torecess bolt or screw
heads below thesurface of a part.
Typically,CH = H + 1/16 (1.5mm) andC1 = D1 + 1/8 (3 mm)
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8olt and Screw Clearances
Countersin9Countersin$s areangled holes that aredesigned to recess
screws with angledheads.
Typically,C1 = D1 + 1/8 (3mm)
)ppendi* 7 gi(es othercounterbore! countersin$and shaft clearance holes.
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Exercise 1054
hat is the nor al fit clearance holedia eter for the following no inal boltsi;es.
ominalsi=e Clearancehole
/JG/J
/G2G/ I
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Exercise 1054
) ; C Soc9et ead CapScrew needs to go through a piece ofetal in order to screw into a plate below.
The head of the screw should be flushwith the surface.
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Exercise 1054
; C Soc9et ead CapScrew 'ill in the following table. Refer to
)ppendi* 7.ead diameter ei#ht o! head
=or al clearance hole dia.C>7ore dia.C>7ore depth
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- D A/ I
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Exercise 1054
; C Soc9et ead CapScrew 'ill in the following table. Refer to
)ppendi* 7.4a*. Head dia eter @ 1.;*;7ore depth
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Exercise 1054
; C Soc9et ead CapScrew 'ill in the following table. Refer to
)ppendi* 7.4a*. Head dia eter ) D .A"A/ I#D.JI4a*. Height of head H D - D A/ I
ormal clearance hole dia.CB8ore dia.C>7ore depth
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E i 1054
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Exercise 1054
; C Soc9et ead CapScrew 'ill in the following table. Refer to
)ppendi* 7.4a*. Head dia eter ) D .A"A/ I#D.JI4a*. Height of head H D - D A/ I
=or al clearance hole dia. C @ % 1
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Exercise 1054
; C Soc9et ead CapScrew 'ill in the following table. Refer to
)ppendi* 7.4a*. Head dia eter ) D .A"A/ I#D.JI4a*. Height of head H D - D A/ I
=or al clearance hole dia. C D - /G2 D /G2C>7ore dia. 7 D @/G2CB8ore depth
E i 1054
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Exercise 1054
; C Soc9et ead CapScrew 'ill in the following table. Refer to
)ppendi* 7.4a*. Head dia eter ) D .A"A/ I#D.JI4a*. Height of head H D - D A/ I
=or al clearance hole dia. C D - /G2 D /G2C>7ore dia. 7 D @/G2C>7ore depth * 1
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