metric fasteners ¨a general apporach

8/20/2019 Metric Fasteners ¨a general apporach

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FASTENERS

A GENERAL APPROACH

Nelson Montaña

31 Agosto, 2015


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Contents

• Historical background

• History of standardization

•

er!inology• "esignation

• Mec#anical $ro%erties


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Historical background

• cre's and nails beca!eco!!on%lace in t#e Middle agesand are seen in e(eryday ite!s suc#

as clocks, ar!or, and furniture+


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History of standardization

•

tandardization of scre' t#reads began!any centuries ago, t#e -rst ti!e acrafts!an '#o car(ed and -led scre't#reads e(er tried to !ake t'o scre's, or

t'o !ated %airs of scre' and nut, co!eout alike+ Ho'e(er, in craft %roduction ofindi(idual t#reads or !ated %airs oft#reads, interc#angeability 'as not a

reuire!ent custo! -tting 'as t#e nor!+

https://en.wikipedia.org/wiki/Craft_productionhttps://en.wikipedia.org/wiki/Interchangeable_partshttps://en.wikipedia.org/wiki/Interchangeable_partshttps://en.wikipedia.org/wiki/Craft_production


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#e -rst #istoricallyi!%ortant intraco!%anystandardization ofscre' t#reads began'it# Henry Maudslay around 1400, '#en t#e!odern scre'cuttinglat#e !adeinterc#angeable t#read !ac#ine scre'sa %ractical co!!odity+

https://en.wikipedia.org/wiki/Henry_Maudslayhttps://en.wikipedia.org/wiki/Henry_Maudslayhttps://en.wikipedia.org/wiki/Screw-cutting_lathehttps://en.wikipedia.org/wiki/Screw-cutting_lathehttps://en.wikipedia.org/wiki/Interchangeable_partshttps://en.wikipedia.org/wiki/Interchangeable_partshttps://en.wikipedia.org/wiki/Screw-cutting_lathehttps://en.wikipedia.org/wiki/Screw-cutting_lathehttps://en.wikipedia.org/wiki/Henry_Maudslayhttps://en.wikipedia.org/wiki/Henry_Maudslay


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• #e -rst serious standardizationatte!%t at t#read design ca!e in14)1, '#en 6ose%# 7#it'ort#

%ro%osed t#e -rst standard8


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•

23 years later, in 149), 7illia! ellers%ro%osed a 90: t#read %ro-le, 'it# t#isc#ange, only one cutter and lat#e isneeded instead of t#ree kinds of cutters

and t'o kinds of lat#es, !aking t#e%rocess easier, uicker and !orei!%ortantly, cheaper to make.


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• *y 1443, %ractically all cor%orations in ;A 'ereusing t#e ellers scre' t#read '#ile on t#e ot#er#and, *ritain ado%ted t#e 7#it'ort# syste!+

• #e %arallel syste! did not %ose a !a/or%roble! until 7orld 7ar &&+ As tanks broke do'non eit#er side, t#e re%lace!ents t#at 'ere beingrus#ed in by A!aerican factories 'ould notinterc#ange 'it# t#e original *ritis# t#reads

because the thread profles dd !ot match.


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•

#e international organization forstandardization


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er!inology

• Scre%& &t is t#e ter! used for a t#readed fastener,'it# or 'it#out #ead so designed as to %er!it it tobe %ro%erly asse!bled in a %re for!ed internalt#readed #ole or ca%able of for!ing its o'n t#readand secured by !eans of tig#tening t#e #ead+

• 'olt& &t is t#e ter! used for a t#readed fastener,'it# a #ead, designed to be used in con/unction'it# a %ro%erly asse!bled by !eans of tig#tening anut+

• #us, t#e di@erence bet'een a cre' and *olt isbased on (des)!( ca%ability, and not t#e actualser(ice a%%lication+


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er!inology

• Cap Scre%& A ter! used to describe a!e.ternally t#readed fastener 'it# a %rotruding#ead, designed to be torued by a s%anner or'renc# and al'ays %receded by a #ead stylesuc# as #e. ca% scre'+

• Stud& A stud is a #eadless fastener, '#ic# #ast#reads at bot# ends+ ne end is inserted intoan internally ta%%ed #oke and tig#tening a nut

on t#e ot#er end induces tensiBn+ &f a stud ist#readed its entire lengt# and a nut is used onbot# ends, it ser(es t#e function of a bolt andt#en classi-ed a stud bolt+


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"esignation

• A !etric & scre' t#read is designated by t#eletter M follo'ed by t#e (alue of t#e no!inaldia!eter D and t#e %itc# P, bot# e.%ressed in!illi!eters and se%arated by t#e !ulti%licationsign, ×


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"esignation


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Mec#anical $ro%erties

Class8 ;sed to designate t#e fastenerstrengt#+ Class is a !aterialdesignation eui(alent to ; ter!

)rade+


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,PREG#NTAS-


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APN/0CE

metric fasteners ¨a general apporach

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