Oke Thread and Fastener

8/19/2019 Oke Thread and Fastener

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Copyright © 2008 by K. PlantenbergRestricted use only

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



Thread %e!initions

External Thread

→ )n e*ternal thread is cut using a die or alathe.



Thread %e!initions

&nternal Thread ,nternal threads are onthe inside of a e ber.

→ )n internal thread is cut using a tap.



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.



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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&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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&nternal Threads→ Cha fers are so eti es cut to allow for

easy engage ent.


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External Threads→ :ou start with a shaft the sa e si;e as the

a or dia eter.


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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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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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,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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'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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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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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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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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%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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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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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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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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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


)ppendi* 7.4a*. Head dia eter @ 1.;*;7ore depth


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Exercise 1054


)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



=or al clearance hole dia. C @ % 1


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Exercise 1054



=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



=or al clearance hole dia. C D - /G2 D /G2C>7ore dia. 7 D @/G2C>7ore depth * 1


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Oke Thread and Fastener