fed_std_h28_2 the standard body screw thread standards

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FEDERAL STANDARD

SECTION 2

- UN AND UNR THREAD FORMS

SCREW - THREAD STANDARDS FOR FEDERAL SERVICES

UNIFIED INCH SCREWTHREADS-

"his s tanda rd w a s approved theAssistantAdministrator,Office of Federal Supply and Services, General ServicesAdministration, for the use of al1Federal Agencies.

Orders for this.publication are t o be placed with General Services

Administration, acting as an agent for the Superintendent of Documents.Single copies of t h i s standard are available at th e GSA Business ServiceCenters i n Boston, MA N ew York, N Y ; Philadelphia, PA; Washington, DC;Atlanta, GA; Chicago, IL; Kansas C i t y , I D; Fort Worth, TX; Houston, 'M;Denver, CO; San Francisco, CA ; Los Angeles, CA ; and Seattle, WA , or fromthe Genera l Services Admin istration , Specifi cation Unit (WFXS), ROOM 6039,7th and D Stree ts , S.W.; Washington, DC 20407.

NO DELIVERAELE DATA RJiQUIRED RY THI S DOCUME3P THDS

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FED-STD-HZBIZA T H m 7777977 0003532 B m

This Federal Standard is issued i n loose-leaf formt o permit the imer t io n o rmnoval of new o r =vised pages and sec t iom.

Al w e m of Federal Standards should keep them up t o date by imert ingrevised o r new pages as issued and removing superseded and canceled paqes.

New and revised pages w l l be issued unde r Change Notices which w i l l benurîbered consecutively and will bear he date of ssuance. Change NoticesshoùLd beretained anrl f i l e d in fro nt of the standard until such t i m as they

a re sqeweded by a reissue of the ent i re s tan dad.

This sect ion was developed t o provide Unified Inch Screw Threads f o r th eFederalServices. It w a s f o m r l y known as "Unified Thread Form m d ThreadSer iesforBolts, Screws, N u t s , Tapped Holes and GeneralApplicatiom". Thepresent issue is a complete revision of FE€)-STD-H23/2 dated 31 Manh 1973. I talsoncludes the materialpreviouslydentified as FHTSTD-H23/3 dated 31March 1973; which was known as "Unified Threads of Special Diaretem, Pitches,a n d Lengths of Engagemnt" . Material fmm Appendices A3 a n d A5 of F€%STD-HBdated 31 March 1978 has beenrevised d is now i n Appendices A and B,

mqec t ive ly , of F'EeSTILH23/2A.

FED-STD-m/2A was p r q a p d by t he Deferme Indust r ial 3upply Center (DLPIIS)and incorporates the h r i c a n National Standard f o r Unified Inch Screw Threds ,ANSI BI .I-1 982. Si gn if ic an t changes fmm the previow issues include hefollowing:

( 1 ) Added UNR, external hread form withmandato y rounded mot.

(2) Revised tole ran ce equir emn ts or ead an d flank angles.

( 7 ) Added requiRmnts f o r cont ro l of surf ace extu re, chamfers, anrJ.

rolled hread ead-ins and run-outs.

(4 ) Added r equ imwnt ha t mpec t ionmthds o racceptabi l i ty aE i naccordance with FEg)-STD-HB/X>.

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F E D - S T D - H 2 8 / 2 A T H W 7777777 0003533 T W

SECTION 2 - Unified Inch Screw Threads -UN and UNR Thread -Form

l . Scope. Th issectionprovides hestandard or unif ied inch screw threadst o be used by t h e 'Federal Services.

1 . 1 Limitations. Only UN and UNR screw threads are covered i n t h i ssection. For UNJ threa ds (con troll ed exte rnal hre ad root with rounded formand increased form minor diameter) see F&STD-H28/4 (MILS-€3979). For UT?"threads(miniature hreads) see FDSTD-H28/5.

1.2 Application.

I 2.1 UN form screw threads. The I J J T thread is intendedfor general purposefasteningagplications. Its external hread root mqy be either f l a t or

rounded.

1.2.2 UN R form screw hreads. The U N R form applies only t o ex te rna lthreads. I ts design form is the s e s th at of the external UN threadexcepttha t the root is required. t o be rounded. UNR threads are applied most of te n tohi_@ volume commercial fa st en er th read s produced by ro l l ing .

NOTE: The mandatory rounded root of the UNR thread greatly reducesthe concentrat ion of stress, hence increases th e fat igue l i f eof threaded parts.

2. Referenced documents.

2.1Government pu bl icat ions . The issues of the oll owing documents i neffect on the date of invi tat ion for bids or request for proposal form a par tof t h i s standard to the extent specified herein.

Federal standards. .

FEBSTILH28/1 Nomenclature, Def in it io ns a n d Letter Symbols for ScrewThreads

FDSTD-H28/6 G a g e s and Gaging forUnified Screw Threads

FEIMTD-H28/20 Inspec tion Methods for Acc ep ta bil il q of UNUNR UKJ,M and MJ Screw-Threads

(Activities ou ts ide the Fede ra l Government mqy ob ta in co pies of Federalspecifications, standards, and corns rcial item descriptions as outlinedunder General Information i n th e Index of Federal Specificatio ns,Standards, andCommercial Item Descrip tions. The Index, which inc lud escumulative bi-monthly supplements as issued, is for sale on a s u b s c r i pt ion bas is ty the Super int end ent of Documents, U.9. Government PrintingOffice, Washington, D C 20402.


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(Ringle copies of th i s spec i f ica t ion md other Federal. specificationsa n d cornnzerbid item descri-ptions required by acti .viti es outs ide the Fed-eral. Government for bidding purnoses w e va.ila.ble without charge from

General Services Admini stration Yusiness Senrice Cen-kers i n Roston, "A;?Tew York, ?J"; Philadsl.~hin., A; Washington, DC; Atlanta, GA; Chicaqo,I L; Kansas C i t y , Mg; Fort Worth, T ; Houston, V: Denver, Cg; San %an-cisco, C4; Los Angeles, CA ; 2nd Sea.ttZe, WA.

(Pedera l Goverment activi-k ies may ohta in copies of FederaI standardi-zation documents, snd. theIndex of FederalSpecifica.kions,3tendzrd.s,and Comercial. Item Descriptions from estab!.isheri d is tr ibut ion D0in-b i ntheir agencies. )

2.2 Other publications. The Pollowing d o c m n k form a par t of t h i sstandmd t o the exkentspecifiedherein.Unless a specific issue isidentified., the issue in effect on date of invi tat ion for bids orreqyest; for

proposal shall apply.

ANST Hrj. 1 Surface %xt;ure - Surface Roughness, Waviness and T J ~ B

4. Cener%lequirements;

4 . 1 8crew threads. TJniP-Led inch screw threads hall. he i n accordancewithA?TSI S1.1-198? md t h i s FederalStmdasd. Only Standarc! Series TJnifj.ed 3crewThreads, l is ted. i n TaIfLe 5jA of AV31 R1 .1-1882, shal l be used. for new design f o rthe Tederal Services unl ess prior approvaJ has been granted b;v t he nrocurementauthori iq odeviate from them Coarse a n d fine hread ser i es are preferred.

4.2 Acceptability. Screw thre ad nspe ction methods fo racceptabil-i .b hall

be i n accordancewith FDSTD-H28/30. The requiredgagingsystem s h d . 1 bespecified in accordance with that, standard.

2


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FE D - ST D - H ZB /ZAH 7477777 0003535 3 W

5. Detailedequiremnts.

5.1 D i e t e r - p i t c h conibinatiom. When standard ize SCRW thr?ads referEdt o i n 4.1 cannotbewed, t h e designershould choose pre fer Ed siz es of sp ec ia lthreads l i s t ed i n Table 3El of ANSI B1 .1-1932. If t h i s is not possible,consideration should be given to the follcawing s&-paragraphs i n the choice ofthr?ad.

5.1 .I Pr?ferr?dnowstandarddiam tem. Whenever pm si bl e, the nominald i e t e r should be selected f mm series of diawter inc rements as follows:

D i e t e r m g e

inch

0.25 t o 0.5above0.6 t o 1 . 5above l . 5 t o 5 .0above 5 t o 16above 6 t o 24

Fi rs t choiceilncrement

inch

O. O 5o. 1o. 25o. 5 '

I o t

Second choiceinc remnt

inch

0.05o. 1O. 2 5o. 5

It is r ec om n de d t ha t d i e t e r s l e s s t h a n 0.25 nch conform t o t h e s t a n d a ds izes as there is v i r t u a l l y no nec ess iS for the sel ect ion of a d iawte r no ti n c l d e d i n those sizes. !CLSO, thecoarse and f ine hreadser ie s prnvi.de amplechoice of diamter-pitch combinations.

5.1 2 Preferr?dnon-standadpitches . Whenever pm sible, hepitchshouldbe selected f mm one of the ollowin g; 40, 3 6 , '32, B, 4, XI, 16, 1 2, 1O, 3,

6 an3 4 threadsper inch. I nte md iat epi tchessho uld be med only whenabsolutelynecessary.Pitchescoamer han 4 threadsper nch are notrecommended. The curves s h a m i n Figur? 2.B. 2 of Appendix B cover theprac t ica l diamete.r limits suggested f o r each pi tch.

5.2 Thread Class Selection.StandardUnified hreadclasses and t h e i rapplications are described i n Section 4 of ANSI B1 . I -1 932. When se lec t ing athread class, consideration should firnt be given t o th e me of a cl ass2A externäì thread with a cl ass 'B internal thread since these classes aredesigned forge ne ra l me. Beforespecifying cl ass ?A/% series, it mwt beconsidered whether the additional. production cost, necessary fo r th e t i gh te r

f i t a n d tolerance is just i f ied. If a f i t locxser th an the st an da d cl ass1A/lR is r e q u i r e d , the non-preferred cl ass 1AR m q be specif ied for anexternal thread of 16 threads per inch and coarser. This special cl asscombines the larger allowance of th e o l d h . r i c a n N ational cl ass 1 thread withthe Unified cl ass 1 A thread toleranc e. See 5.2.2 f o r class 1AR allowance.

'5

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__

FE D-STD-HZB/ZA H m 3777777 Ö00153b 5 m

5.2.1 Replacerrents forob so le te Amzrican Natio nal hreadclasses. When

threads specified with the obsolete Amrican Nationd-thIwd classes are t o bereplaced by unifiedhreads,heollowinguidelines are provided:

a. h r i c a n National class 1 coame hread series (NC-1) is approxi-mtely equiva1en-b t o Unified class 1A/?R se ries. Cl ass 1 f inethread series (NF-1) is approximtezyequivalentdimmionally t oUnified class 2A/B series. StmdaldUnified se ries threadsshouldbe comi dered prior t o appmval of replacement by non-standardthreads,

b. h ican National class 2 coarse hread series (NC-2), 8 thRadseries (8N-2), 1 2 thread series ( 1 ZH-2), I6 hrmd series (16N-2),anCi ex t r a f ine thpad series (IlEE"2) are most nearlyequivalent t oUnified series lNG2A/2B, .SUN-2A/B, 12UN-2A/2B, 16VrcJ-2A/2R andU?WE'-ZA/B respectively. Cl ass 2 fine hread series (NF-2) isapproximatelyequivalent di m mi on al ly to Unified clas s 7A/Yseries, but he me of class 2A/B se ri es should be consideEdp r i o r t o approval of Epl ace wnt by c lass ?A/%.

c. AwricanNational class 3 se r i e s NC-3, NF-3, NEZ-3, 8N-3, 1 B -3 and15N-3 ar e most nearly equivalent t o Unified class '3 s e r i e sUNG3A/3B, UNF-?A/%, UNEF-3A/3B, SUN-3A/%, 12UN-'3A/3 nd15UN-3A/33, respectively .

d . There is no Uni fied, hreadclassequivalent to th e old AmricanNational cl&s 4 which r e q u i r e d se lec t ive f i t of parts du e t o t h epms i b i l i Q of i n t erfe rence.

5.2.2 T h P d allmance and tolerance. Al l owances and tolerances pecifiedfo r st an da nl Unified thread classes are described in Se ct io n 5 of ANSI B . I -1932. For he special external t h m d c l a s s 1 AR tolerances are he sa~e sf o r c l a s s 1 A and 'allowances are as f ol l ows:

-

ThEads per inch 1 Class 1 AR allowance

inch15

O O0230O. 00242O 002140.001s

o.00440.0074

- 4 0.0054

TO complement, paragraph 5.6 of ANSI B? .?-1gS2, recomwnded tap d r i l l s i zes andhole s ize limits before threading , for d i f fepnt l e n g t h s of engagewnt, areincluded i n Appendix A .

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F ED- STD- H2 8 /2 A T H m 7777777 0003537 7 m

5.3 Designation.DesignationofUnified s c m threads is in accordance w i t h

sec t ion 6 of ANSI R1 .I-1 932. Wominal s i z e s h a l l be stated i n decimals. Thesynibol UNS is applicable t o aq r thread:

(1) having theba si c Unified hread form

( 2) with limits based upon Unif i.ed for nul at iom , and

(3) -which is not in he stand ard series l i s ted i n Table 3A o fPNSI BI 1 -1 932.

5.4 L i m i t s of siz e. See se ct io n 8 of MSI BI .I-1 992 f o r limits of s i z e ofsta nda rdx d pre ferr ed non-standard th pa ds and f o r i n f o m k i o n Lsed f o rcalculation of non-standarrl hread s i z e limits which are not tabulated. For

class 1AR calculate as f o r c l a s s 1 A except allowance is tab ula ted in 5.2.2.The follo wing exmp le j.llustra-tes the p m e d u p necessaqr to ca lc ul at e th elimits of si ze of a'non-standard thread; this follows the outlines in tables 1 Aand 113 O f ANSI BI -1-1 932:

Exte rnal hread , 2.500 - 23UNS-2ALen.&h of engagemnt, 1 inch

%aximummajor d i e t e r =Nominal si z e - allavance( s ec t ion 13 of ANSI BI . I-1 932)

= 2.m 0.001 4 ( f rom table 32 o f ANSI BI . I -1 932)= 2.49%

Minimum major diameter =M a x i m u m major d i e t e r - tolerance(Section 13 o f ANSI BI .l-1932)

= 2.4935 - 0.m5 (from table 31 of AVSI BI .l-1932)= 2.4921

Y k m i m u m p i tch d i a mt e r =Maximum major d i e t e r -( t ab le 6 , col. 1' 3 o f AISI9 .1-1932)

= 2.4935 - 0.0232 ( rouw3ed f r o m O. O23197)= 2.4754

Minimum pi tch rliarneter =M a x i m u m pi tch d i e t e r - tolerance(sec t ion 13 of ANSI BI . I-1 932)

= 2.4754 - 0-005 ( f mm table 34 of ANSI B1 . ? - I 932)= 2.469

Nomina ( m a x i m u m ) minor =Maxi mummajor d i e t e r -d i m t e ( t a l e 6 , C O L 3 5 o f DISI"r. I - I92)

= 2.4936 - O.OY7 ( rounded from 0.03366)

= 2.4999

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Internal thread 2.500 - BUNS-2B

( to mte wi th the above th re d )

Minimum minor diameter =Nominal s i ze -(table 6 , col. ?29f ANSI B1 .I1 932)= 2. %XI - 0.037 ( rounded f r o m O OB 6 6 )= 2.4613 which is rounded t o 2.461

Maximum minor d i e t e r =Yinimum minor di am te r( + to le ra nc e(sec t ion 13 of ANSI BI 1-1932)

= 2.4617 + 0.0063 (fmm table 39 of ANSI BI .1-1932fo r le n g th of engagernent of 0.4D)

= 2.4675 which is rounded t o 2. $8

Minimum pitch diameter =Nominal size -( tab le 6 , col. I of ANSI S1.I1 932)

= 2.W

- 0.032 ( rounded f r o m 0.0~197)= 2.4763

Pilaximum p i t c h d i a w t e r =Minimum pitch d i a t e r f tolerance(sect ion 13 o f ANSI BI .I1 992)

= 2.4758 f 0.0073 ( f m m table 77 of ANSI 'B1.1-1%2)= 2.4841

Nominal (minimau) mj r =Nomina S ized i a m t e r

= 2.m,

Factors used in the des i in of threads, particularly special -t ,hreds, a p

pE se nt ed n Appendix B. It is t o be noted that devia tiors f r o m standardtolerances f o r major di am te r of the external thrmd aril f o r minor dians ter ofinternal thEad m q be necessary in order to arr ive at the optimum design.

5.5 Surface t extura

5.5.1 The th read s sh al l have a smooth fi ni sh mbe fre e from f l ms andotherdefects,such as fins, nicks ard bu rr s, ha t would make them m u i t a b l ef o r t h e purpose ntended.

5.5.2 W o h m h i p s h a l l be cornistent with the tolerances specif ied herein.Surface texture of threads pmdaed to th is s t an da d sh al l not exceed 100mic minch arithmetical ave rage roughness (Ra) f o r cut threads and 53

misroinch (Ra) for rol led and grouml th m& in ac co da nc e wi th A?lSI B45.1

NOTE: Coarse and finepitch hEadswith rough surface t e x t u r e are mopl ikely ocms-thIparl. Thpadswi th chamfe-red ent erinq ends have the le a s ttendency t o cms-thrPad when asse&lea with paver tools.

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F E D - S T D - H Z B / Z A H W 7 7 7 7 7 7 7 0003537 O m

5.6.1 -U1ente ring ends of fas teners and threaded components sh a l l have45' chamfers approximakely) Prom minor diameter of ex ter na l threads and

major d i e t e r of internal.. hreai(.s,unlessotherwisespecified.

F;. Rolled hreads.

5.7. I Comple%el_y ormed thren$s. A completely forined. thr ead .foll_ows th ethread profil e, wit hin the tole rance zoneover an a x i d distance of one pitch.See figure 2.1 .

5.7.2 Inconplete formed threads.

5.7.7.1 The lead- in th read is measured from the end OP the product t o thestart of the f i r s t complete thread where the major diameter is eq-ual. t o the

m-inixum a,llmmble major diameter m d the thread root iseq-ua.l-

to themax_i.mum

minor diameter. This shouldnot exceed 2P. See figure 2.2.

5.7.2.2 The run-out thread is mam.red between th e tr an si ti on po in t of theproduct an d - the first, thread root which is completely fòrmd, where t h e minordianeter equals the maxi mumpermissib1.e minor 'diameter and -the m j o r diameterof the last fü!.ly for md thr ead equal s the minimum permissible major diameter.'hen root radius is specified, the las t completely formed root a t the minordiaLwter must meet th e requirement. See f i g r e 2.7 for f u l l sha.nk fastener,f i q r e 2.4 for pitch diameter shank fastener, figure 2.5 for shoulder bolt,f igure 2.6 for oversize diameter shark fastener m d f igures 2.7 and 2 . R f o rthreaded t o head fasteners.

6.1 Supersessionnote. Inaddit ion t o superseding FF'srRTILIJ28/2 dated. 71Narch 1978 and FLWP!!!D-F2P/'i; dated 71 Narch 1978, t h i s doamnt , a lso supersed.esAppendices A3 and A5 of FE&STD-V8 d a t ed 31 P4arch 197%

Custodians

A r m y - ARTSavy - A?

A ir Force - 11

Review Activities

Army - CR,M ,ER,Pl?Air Force - 15,W

TJser Act iv i t i e s

Arqy - AT ,M I

PREPARING A C T I V L 9

DLA-I S





r d BASICMAJOR DIA

L-" /- c.

. M I N M A J O RDI A

d e BASIC PITCH DIA

d 3 MAX ROUNDED

R OOTMINORDI A

L 3 MIN ROUNDEDROOTMINORDI A

FIGURE 2,l COMPLETELY FORMED EXTERNALTHREAD

L E A D TH R E A D S = 2 P M A X

"Id M I N M A J O RDI A

d 3 MA XROUNDED

ROOT MINOR DIA

Y C H A M F E R A PPROX 45O

END OF SHANK

FIGURE 2.2 INCOMPLETE FORMED EXTERNAL THREADS,LEAD-IN THREADS

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F E D - S T D -H 2 8 / 2 A H m 7777777 O O O L 5 4 L 7 m

FED-STD-H28/2A

FIGURE 2.3 INCOMPLETE FORMEDTHREADS, FUL L SHANK

FASTENER -STANDARD DIAMETER

P- MA XUNOUT = 2PO M P L E T EH R E A D S

MIN RUNOUT = 0 . 6 P

" 7 3 0 . J

d MINM A J O R DIA

d 3 MA XROUNDED

ROOTMINORDI A

FIGURE 2.4 INCO MPL ETE FORMED THREADS, PITCH DIAMETER

SHANKFASTENER



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. F E D - S T D - H 2 8 / 2 A TH 9 7 7 7 7 7 7 7 0003542 O 9

FED -STD -H28/2A

d MINM A J O RDI A

d 3 M AXROUNDED

ROOTMINORDI A

FIGURE 2.5 FUL L SHANKFASTENER-STANDARDDIAMETER.

OPTIONAL CONFIGURATION (SHOULDER BOLT)

t a

MA X RUNOUT =2~ +(OVERSIZEINCREMENT +2 TAN 8 M I N )

C OM P L E TEH R E A D S -

t I N R U N OU T =IP " (OVER-S I ZE N C R E M E N T f- 2 TAN

8 M A X ) i

L 12 OV E R S I ZEINCREMENT

N OTE :

8 = TR A N S I T I ONTA P E RA N G L E

d 3 M A X R O UN D EDROOTMINORDI A

FIGURE 2.6 FULL SHANKFASTENER-OVERSIZEDIAMETER

IO




F E D - S T D - H 2 8 /2 A H m 7 7 7 7 7 7 7 0001543 2 m

FED-STD-H28/2A

r NDERHEAD SURFACE

4 W MAX 2P -I- MAXILLET RADIUSOMPLETEHREADS -W MIN=IP+MAX -FILLET RADIUS

-

d MIN MAJ OR DIA

r MIN FOR THREAD ROOT

FIGURE 2.7 F U L L S HA N KFASTENER -THREADED TO HEAD

r NDERHEAD SURFACE

4 W MAX 2P -I- MAXILLET RADIUSOMPLETEHREADS -W MIN=IP+MAX -FILLET RADIUS

-

d MIN MAJ OR DIA

r MIN FOR THREAD ROOT

FIGURE 2.7 F U L L S HA N KFASTENER -THREADED TO HEAD

UNDERHEADURFACE

W MA X =2P +MAX FILL ET RADIUS"OMPLETE HREADS -RADIUS

\

d MIN MAJ OR DIA

/

-v"-----

F I GURE 2.8 PIT CH DIA ME TE R SHANK FASTENER-THREADED TO HEAD

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APPENDIX A

12



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F E D - S T D - H 2 8 / 2 A H W 7777777 0003545 b m

20.2.3 Pexent of thread isted n ables is the ra t io n penen t of the

ac%ualeight of thread t o t h e value 0.7W, his value is the basic threadhei,ght of th e ob ol et e Amrican National Thread Profi le. Sinc e he basicheight of a Unified Thread Profi le is 0.52!3, the m a x i m u m penent. threadpermissible is 83. 9. Due t o allowances f o r d r i l l s t o cut oversize o r du e t olack of availability of drill s with in specif ied minor d i e t e r l imits , tapd r i l l s l is ted in tab les II.A.l and II.A.2 may show grea te r th an 89.3% threads.This indicates that the d r i l l size is smaller than the minimum thread minord ia r e te r aril additional machiningof the hole may be necessaly in or de r tope mit economical tapping.

30. Recomndedhole size limits before hreading.

39.1 General. For hor t eng thof engagem?nt, th ehole d i e t e r required

pr io r to thr ea di ng should be held near the minimum limit t o maximize threadheight or mximum jointstrength. PS length of engagemnt ncreases, it isdvantageous t o increase the hole diawter for mre economical tapp ing withless risk of ta p breakage.Therefore, he ollowing ecomndatiom weredeveloped (also see 30.2 below) :

Length of Engagemnt

Up t o and including 0.33D

Above 0.739 t h r u 0.67D

Above 0.673 t h r u l .9

Above l . 9 t h r u 3.0D

Minimum Hole Si5e M a x i m u m Hole Size

Minimum minor d i a Min minor d i a plusI /2 minor d i a tolerance

Min mino r d i a plus Min minor d i a plus

1 / 4minor dia, tolerance 3/4 minor d i a tolerance

Min minor d i a plus Max minor di a ( min minor1 /2 Minor d i a tolerance d i a plus tolerance)

‘Minminor d i a p l w ax minor d i a plus I / 43/ 4minor d i a tolerance minor d i a tolerance

(See 30.2)

Prom the foregoing it w i l l be seen that the diffe rence between limits in eachrange is t he s e nd eqd t o half of the minor d i e t e r tolerance.This is ageneral rule. However, the minimum dif fe rences for s izes below O. 25 n are

equal t o t h e minor d i e t e r olerances given in tables 39 and. 40 i n ANSIBI .1-1932 f o r lengths of engagemnt t o and i n c l d i n g 0.33D. For engths o fengagement gr ea te r tha n 0.37D f o r s i z e s 0.25 i n and lar ge r, th e minimum valuesare adjusted s o t h a t the dif fere nce between limits is never less than 0.0040in .



--``,,```,``,,`,``,,,,-`-`,,`,,`,`,,`---



50.2 Tabulated. d a t a . Recommend.ed hole size lfmits f o r standard TJniPied

3hreads md som special. (TJVS) threads me given in ta bl es LI'.p\.'j; and II.A.4.For otherspecid. hreads,ca lcul ate n a.ccordance with 70.1 above; u s e m i n i m

ninor d.iawter a n d tolerance from tabl-e ?R o f APITSI R1 . -IW?,r caI-cx1.a.te i naccordance wi$h section 8 o f AJTSI €?II-1 9.82 using apnropriate tol-ermce f romtab1.e 39 or 40 of A N S I Pl . l - lW2 for tolerance ra t io o f . 1 or fromPormt .hs i np a r c ~ a p h.8.2 of ANST R1.1-1982. Tabulaked hoTe sizes md hole sizescalcu1.ated i n accorciance $ r i t h SO. 1 are not mandatory unl ess the threaddesi,pns.tion s ta tes the modified. minor d iamter limits and the d.esipns.*ionX 7D i n accordance withgmagraph 6.7 i n A F E T F1.l-1982. Tf modified minord i R m t w L i m i t s are not speci f i ed, acceptance will be i n .accordance w thstand-ard minor diameter l imits .

V?!"?: Recommended-mnxjmum hole sizes i n 70.1 , *or 1end;ha of enW\eEent;,greater than 1.5D 8re outsidestandardmhordiameter limits. They m e n o t

inchded in takles T I . A . 7 an d T.I.A.4. ?se of a minor ciiameter l a r p r thanstmdarcl will r e su l t in R reduction i n shear area of the external threads ofthe m.%ing art. I f mnuf.wt,uring process permj.ts, maximum hole sizebeforethreading shal1.d be mintained ak the high end of th e slxnderd minor dimeterlimits.

70.7 Other considera%ions. When tappinp rel-a.tive1.y soft; materials,especially with 'ine pitch t h rmds , there i a a tendency for the materid- t o hesqueeze?. c7own.tumrda the r o o t of t he tap s o t h a t t h e minor d?_meterof thet a p p e d hole mav become smaller than the d i m t e r of the drill-erl ho1.e. T t ma~?benecessary t o try a different; s i z e d r i l l or different; style tsy! t o assure asatisfactory thread.

14


--``,,```,``,,`,``,,,,-`-`,,`,,`,`,,`---



F E D - S T D - H 2 8 / 2A H m 7777777 0002547 T m

T hr ead s i z e

.210

i n.o80

.O73

,073

.O80

.O80

.O89

. 99

,112

.112

.125

.125

.138

.138

.le4

.104

.1 m

. lm

.210

.210

-

rhreadcpe rinch

-

80

04

72

50

04

48

50

40

48

40

44

32

40

32

30

24

32

24

28

32

FED- STD-H28/2A

T A B L E I I .A .1 - a p d r i l l sizes,Unified screw t h e a d s , c l a s s e s 1B an d 28

1 I-

h i g -l a t i m

-

U N F

U N C

U N F

U N C

U N F

U N C

U N F

U N C

U N F

U N C

U N F

U N C

U N F

U NC

U N F

U N C

U N F

U N C

U N F

U N E F

-

Classes 1 B and 2Bminordiameter , I T a pr i l l s o n dercent of thread

ilinimum

i n0.0405

.O501

.O580

.O607

,0691

.O704

,0797

.O849

.O894

.o978

.loo4

,104

.111

,130

.134*

.145

.150

.171

.177

.182

internal threads

Percant-

threado f

1/

83.1

83.3

83.1

83.2

8; .3

83.5

83.2

83.4

83.5

83.4

83.3

83.8

83.1

83.8

83.1

83.1

83.8

83.1

84.1

83.8

Maximum

i nO. 0514

.o823

.o835

.O737

,0753

.O845

. 88 5

.OL)39

.o908

.lo82

.lo79

,114

.119

. .139

.142

.150

.164

,181

*186

. 1 w

l -thread I

53.0 {FI i n

#48

53.0 1 5 4 7

'53.9

#45'#40

#40

' 44

~ #44#45

55.7

'Y43

$i;

56.2#4 2

,Y41

I #4 0

57.9 $ 3, #37#38

57.9L 8 3 0

#37

'#37

#36

R34#33#e4

58 .5 ' #33#32

01.0 #29#29

01.0[c8

( 8 2 7

02.8 #25X 20

X24

59.1 y35

,#23

04.0#21

' Y 2 2

#20

04.7

#16

64.7

, #13$i:#14

04.0 I#13

Y1 2

O. 0405i n

.O409

.O550

.O595

.O595

.O625

.o870

.O700

.O730

.O700

.O730

.O700

.O781

.O785

.O810,0820.O810.O820.O800

.O800

.O935

.O938

.O890,0935.O938.OBBo

.o980

.o995

.lo15

.lo40

.lo15

.lo85

.lo40

,1040

.lo85,1094,1100.1110,1130.1110.1130.1160

,1300.1300,1405.14O6

.1440

.1470

.1495

.1520

.1540

. I 5 0 2

.1590

.o8w

.i570

.isla

. m a

.i770

.1770

. m a

.m a

.mc

.1719

.lm

. 1 m

.lm

.1m

.M76

T ercentof

thread

8381

89077558

8209567904

8677700703787350

8071575085080759

83

- 7279

05807163

84

7870080702837768

69780565

8579

7075

6683817671

827972078478730784767067

Probableu

warsize,mean

0.0015i n

.o015

.o015

.o015

.o015

.o015

.o017

.o017

.O017

.O017

.o017

.o019

.o019,0019,0019,0019.o019.o019.o019

.o019

.o020,0020.o020.o020

.o020

.o020

,0020

.o023

.o023

.o023.W23

.o023

.o023

.o023

. 029,0029.o029*0029

.o032,0032. 032.o032.o032.o032.o032.o032*0032

,0035,0035.O036*0035.o035.o035* 0035.o035.o035.o035.o035.o035

-'robable

holesize

0.0480i n

.O484

.O505

.o810

.o810

.O840

.O887,0717.O747.O717,0747

.O779

.O800

.o804.O829

.O839

.O829

.o839

.O879

.O878

.c910

.o955

.O958

.o910

.o955

.O958. 980

.lo03

.lo18,1038.lo83.lo38,1063* 1088

.lo83

.lo88.1120

.1126

.1136

.1150

.1130,1150.1188

.1389

.1389

.1434

.1435

.1472

.1502

.1527-1552.1572.1594. l m 2.le22.M42

.1754,1705.1805. l a 5. l m 5. l m 5.1M5,1885,1855.1885-1910.1925

Percent

threado f

J/

7471

81

6759

50

7502497056

787009Bo

6950

0548

740551507801Bo52

707165

7258

6355

78

72040300557509Bo

62705757

787409640175736804

7573

00Bo77706059

6875

6258

See ootnotesat en d of table.

,

15ided by IHS Sold to:HOLTEC INTERNATIONAL, W0847024


- - ` ` , ,

` ` ` ,

` ` , ,

` ,

` ` , , , , - ` - ` , ,

` , ,

` ,

` , ,

` - - -



I FE D - ST D - H ZB /ZA H W 7 7 7 7 9 7 7 O O O L S L I B L W-111-

~ ~ ~ ~

FED-STD-H28/2A

TABLE I I . A . 1 - ap dri l l sizes, Unified screw threads, classss 1B and 28 Continued

Thread ri;

i n

a 250

* 250

.250

* 250

.312!

.312!

.312!

.312!

.312!

.312!

.375

.375

.375

.375

I378

.375

,4375

.4376

,4376

.4375,4375

,500

.m

.mm

.m

.m

.ti626

. 82 5

.5626

,5626

.M125

.S626

. M 2 6

.e26,625

,625

,625

a626

A 2 6

.e26

.e26

rhread

inch

per

20

28

32

36

18

20

24

28

32

36

16

20

24

28

32

36

14

16

20

28

3 2

12

13

2016

2832

12

16

18

20

24

28

32

1112

16

18

20

24

283 2

a t end-

DeaIqnatbl

-

UN (

UNE

UNE1UN 8

UNC

UN

UN F

U N

UNE1U N 8

UNC

U N

U NF

U N

JNEFUNS

UN C

U N

U N F

JNEFU N

UN SU NC

U N FN

JNEFU N

UNC

U N

U N FUNlNEF

U NU N

UN CUNU N

UNFU N'NE FU NU N

able.-

1 Classes 18and28 minor diameter,

internalhreodr I Tap drills and percent of thread

Minimum

i n

.ee

,211

-216

.220

.252

.258

.267

,274

.279

.282

,307

,321

,330

,336

.341

.348

.380

,370

,383

.389S404

.41C

,417.432*446

,488,461

.472

,485

.502

-508

.517

,524

,629

.527* 535

,557

,568

.571

.m

.m,581

Percent

threadO f

83 .

84 . :

8 3 . 1

8 3 . 1

83.1

83 f

8 4 . 1

83.c

82.5

84.:

8 3 . 8

83.1

83.1

84.1

83.8

83.1

83.5

83.1'

83 .8

83.0

82.. 8

83.1

83.1

83.183.8

84.183.8

83 .B

83.1

83.8

83.9

8 4 . 1

83 .O

82.8

83 .O83.1

83.8

83.1

83.1

83.1

84.183.8

Maximum

i n

,207

.220

I224

.228

.265

.270

.277

.282

.286

.289

.a21

.332

.340

.345

.348

,352

.376

.384

-395

.407

.411

.428

.434

.457

.446

.474

.470

.490

.m

.S15

,520

,527

,833

.S36

.546,553

,871

.S78

a 582

,890

.595

. 5 w

I

Percent1of Drilliz e

thread I 1 thread I mean ' I size I thead

66.1

64.7

64.0

6 6 . 5

65.8

68.4

65.6

68.7

65.3

6 5 . 1

88 . 5

88.2

6 4 . 7

64.7

6 4 . 0

6 3 . 7

66.3

65.9

65.4

65.765.3

66.5

06.088.588.2

64 .O64.7

67.0

6 5 . 9

65.8

65.4

68.6

65.7

65.3

88.988.5

88.5

65.1

68.2

64.7

6 4 . 764 .O

i n.lee(-18%.201(.2031.204(-205:

. 2 1 s

.213(

.218f,221c.221c

.W O

,2570,2010

,2610

.2680

,2880

.2770,2720

,2770

.2812

.2810

,2812,2810

.2e54

.3125,3180,3230

,3320.3320

. 3 3 m

.3380

.3438

.a438

.3480

.3480

. 3 m

.3594,3750,3770. 3 m

,3808.4040,4040. m 2

,4130.4218,4218.4375.4531,4688.M88

. 4 M 4,4688

.5ooo-5082

. m 2.5ooo

-5158.5156,5203.5312,5263.5312

. M 6 8,5312

. W2 5,5687

,5087. M 2 5

-5781

15828,5781

* 5938,5838

8379757271688067

7 177

80

777 185

7872

807566

776867

787775

7773806678677867

6777

75

8884

7 677

78

72728377

80

7872

77

6772

77

87727768877872877887

7778

7278

6977

87787287786777

i n.003E.003E.WE,0038*0038, 0 0 3 8,0038

.o038

.o038,0038

. 038

.o038

. N 4 1

.O041,0041

.m1

,0041.o041

.O041

. m 2

.o042

.o042.o042

.o042

.m4

.o044

,0044, 0 0 4 4

.o044

. W 4

.o044

. m 5,0045

,0045,0045

.o046

.o046,0046.o046.o046

.o046,0046S0046.o046

.o047,0047.o047.o047

.o048,0047

.o048

. W 8

.o048

. W 8

.o048

.o048

.o048

.o048

.o048

.O048-0049.O048.O048

.o048.O048

.o049,0048.o049,0049I0048.o049. W4 8I0048a 0049

.o038

in

.202l

. 891

a 200f.m1

.207E

.200:,216E.222f* 222fI224f,224f

I280E. M 5 1I260E-2651,2701

,2701.2761

,281 1,2811

,2852.2854

,2852.2854.28M

.3168

.32W

.3274

.3364,3364

.3434

.3434

.3483,3483,3525,3525

,3626.3640. 3 7 w.3816

.3952

,3808

,4088.4088,4108

,4177-4286.4288.4422*4578.4736.4736

,4736,4882.m8.5110.m8*6110. 5 2 M-6204

.5361.5261

. m 1 2-5361

.5361,5518,6874

*5874,5736-6830.6830

a 5987,5877

,5987

,6736,

77

7073

6566

63725967

!g6572

80

6573

6778

685 8

5 859

678763

726773

7 159

8868

5868

6255

798 1

7 169

65

72

6 27 188

7668737165

6 557

6882

637 1

8071657869576765

68757 1e380718570695765

16




FE D -ST D -H ZB/ ZA H m 7 7 G 9 7 7 0001.549 3 m

FED-STD-H28/2A

T hr ead s i m

in

.6875

.ti875

.6875

.6875

.6875

.6875

.750

.750

.750

.750*750.750

.I3125

.8125

.S125

.S125

.a125

.a75

.a75

.a75

.a75

.a75

.a75

.a75

.9375

.o375

.9375

.9375

.9375

1 .o00

1.o00

1 .o00

1 .o00.OOO

1 .o001.o00

1 .M25

1 .o6251 .o825

1 .o8251.C025

1.0625

1.125

l. 125l. 125

l. 125l. 125

1.125l. 125

l. 1875l. 1875

l. 1875

l. 1875

l. 1876l. 1875

1.2501.250

1.250

1.250

1 .Z N1.2501.250

rhreadspe rinch-12

2016

242832

10

1216

2820

32

12

2016

2832

129

14

16202832

i2

2016

2832

8

12

1416202832

8

12

16

2018

28

7

8

12

16

18

2028

128

16

182028

78

12

1618

2028-

TABLE I I . A .1 -Tap dr i l l s ires, Unif ied screw threads, classes18 and 28 -Continued

Deria -nation

l-U NU N

UNEFN

U NU N

UNC

U N

U N E FN F

U NUN

U NU N

U N E F

U NN

U N CU N

UNB

U N E FN

U NU N

U NUN

U N E FU NU N

UNC

U N F

UNS

U N E FN

U NU N

U N

U N

UNEFN

U NU N

UNCU NU N FU N

UNEFU NU N

U NU NUN

UNEFU NU N

UNCUNUNE'U N

UNEFU NU N

table.~

Classes 18and 26 minar diameter,

internal threads I Top dr i l l s and percent of thread

Peroent

threodMaximum

Ii l l

.B97

.620

.633

.642

.654

.649

.642

.660

.682,696.711.716

.722

.745

.758

.774

.779

.755

.785

,798

.807-

.a21

.836

.841

.a47

.870

.883

.a99

. W 4

. 65

.910

.923

.932

.946

.B61

. M 6

.927

.972

.9951 O021.O081.024

.i70

.gm1 .O351 .O571 .O65

1.0711.086

1 .O521 . W 71.120

l. 127l. 1331.149

1 . W 51.115

l. 160l. 182l. 190

1.1861.211

83.6

83.183.984.183.082.5

83.1

83.1

83.883.184.183.8

83.6

83.983.1

83 O82.5

83.183.1

83 O

83.883.184.183.8

83.6

83.183.o83 O82.5

83.1

83.1

83 O

83.883.184.183 8

83.4

83.6

83.183.883.983.0

83.5

83.1

83.183.8

83.183.184.1

83.483.683.1

83.883.983.0

83.583.1

83.1

83.8

83.1

83.184.1

,

i l l

.615

.634

.645

.652

.657

.661

.663

.678

.696

.707

.720,724

.740

.759

.770

.782

.786

.778

.803

.814

.a21,832.a45.a49

.M5

.W

.a95

.e07

.911

.a90

.928

.938

.946

.957

.970

.974

.o52

.990

1.W1 .O151 o201 .O32

.B98

1 .o15

1 .O531 .O71

1 .O78

1 O821 . W 5

1 .O771.1151.134

1.140l. 145l. 157

l. 123l. 140

1.178

l. 196l.203

1.2201.207

P e r c e n f

threadhreadD r i l l size

67 O

65.965.465.665.765.3

67 O

66.5

66.5

64.766.2

64 O

67 O65.965.465.765.3

67.266.5

65.7

66.5

64.766.2

64 O

67.0

65 B65.465.765.3

67.7

66.5

66.8

66.566.264.764.0

68.0

67 O

65.965.865.465.7

68.4

67.7

66.5

06.5

65.1

66.264.7

68.0

65.967.0

65.865.465.7

68.467.7

66.5

66.5. 65.1

66.264.7

17

I Li n*5938.6094,6250.6406

.6562

.6406

.I3562

,6406.6562,6562,6719.W75.7031.7188.7188

.7344,7500.7656.7812.7812

.7656

.7812

,7969.7969.ao24,8125

.a281

.a125

.S438*8438

.S438

.a594

.a750

.B906

. m 2

. W 6 2

.a594

.S750

. m 2

.9219

.9274

.9375

.9531,9688.96W

.9219

.9274

.9375

.9688,9844

1 .oooo1 .oooo1 .O1561.0312

.9844

.M88

1.oooO1.03121 .O4691 .O6251 .o8251 .O7811 .O7811.0938

1 .o6251.09381.1250l.1250l. 1406l. 1406l. 1562

1.O938l. 12501.15521.1719

l. 1875l. 1875

l.2031l. 20311 .2188

.gal9

87

7772

72876777

8472877277726777

777.2

6772

77

7687

7284786777726777

877277

6772

77

87778772847877726777

878377877277877267

84767787727787657267

778777

87657267

847787727787657267

'roba l ew er s k e ,

m a n

Probableholesi 70

Por c n t

threado

11



--` ` , ,` ` ` ,` ` , ,` ,` ` , , , ,-` -` , ,` , ,` ,` , ,` -

--



F E D - S T D- H Z B / Z A H m 7 7 7 7 7 7 " ? 0001550 T W

FED -STD -H28/2A

T A B L E I I . A . 1 - T a p d r i l lsizes, Unified screw threads, classes 18 and 28 -Continued

Thread ai

i n1.312

1.312

1.312

1.312

1.3121.312

1.375

1.375

1.375

1.375

1.375. 1.375

1.375

1.437;

1.437!

1.437:

1.437!

1.437:1.437:

1.437t

1.500

1.500

1.500

1 .5001.500

1 .500.500

1.5625

1.5625

1.M25

1.M251 .B325

1.M25

1.825

1.825

1.625

1.ea5

1.625

1.625

1.m75

1 68751 .O875

1.6875

1 8875

1 .8875

1.750

1.750

1.750

1.750

1.7501.750

5

5

5

5

55

i

iiii

Se e footnotes at end al

Threadperinoh

8

12

16

18

2820

6

8

12

16

18

2028

6

8

12

16

2018

28

6

8

121618

28.0

6

8

12

1618

20

6

8

12

16

18

20

6

8

12

16

18

20

5

6

8

12

2016

U N

U NU N

U N EU NU N

UN (

U N

U N €U N

UNElU NU N

U N

U N

U N

UNElN

U NU N

UN C

U N

U N FU N

JNEE

U NN

U N

U N

U N

U NJNEPU N

U N

U N

U NU N

JNEbU N

U N

U NU NU N

l N EFU N

UN C

U N

U N

U NU NU N

le.

-

-T Classes 16 and 28 m in a diameter, Tapri l ls and percent of thread

internal threads

Minimur

in

l. 17;

1.22:

l.24:

1.25:

1.25El. 274

l. lYt

1.24C

1.285

1.3071.315

1.3211 .336

1.257

1.302

l. 347

1.3701.3771.3831.39Y

1.320

1.365

1.4101.4321.440

1.4611.446

1.382

1.427

1.472

1.4951.502

1.508

1.445

1.4YO

1.535

1.557

1.566

1.571

1.507

1.5521.597

1.620

1.627

1.633

1.534

1.570

1.615

1 .860

1.6821.696

Percent

threadof

1,

8 3 .

83

83.

83.

8 3 .

83 '

83.

83.

83.83.1

8 3 ,

8 3 ,84.

83.1

83 .'

83.t

83.183.t83 S

83 (

83.

83.1

83.1

83.883.183.184.1

83.4

83.4

83.6

83.183.8

83.9

83.1

83.1

83.1

83.883.1

83.1

83.4

83.483.683.1

83.8

83.9

83.1

83.1

83.1

83.183.883.1

Maximum

1.201i l l

1.24c

1 .a50

1.265

1.282.270

1.225

l. 263

1.303

1.321

1.328

1.332l. 345

1.288

1.327

1 .365

1.3YO1.384

1.4071.3Y5

1.350

1.3YO

1.4281.446

l. 4571.452

1.470

1.413

1.452

1.490

1,5091.516

1.520

1.475

1.515

1 .553

1 .S71

1.578

1 .B82

1 .538

1 .5771.615

1.634'

1.640.

1.645

1 .B68

1.6"

1.640

1.678

1.6961.707.

T Percent-o f "I Dri l l s Ize

I thread IL I

*

1 8

inl. 171C1.187:

l.23441.2185

1.25OCl. 25oc

1.26561 ,2656

1,2812

l. 18761.20311.21881.2344

l. 28121.2969

1 .a1251.3125

1 .S2811 .a281

1.3438

l. 26561.2812

l. 29691.31251.34381.35941.3750

l.39061.3750

1.4062

1.32811.3125

1 3594

1.4062l. 3750

1.4219l. 43751.4375l. 45311.4688

l. 39061.40621.4219

1.46881.4375

1.4844

1.50001.5oOo1.51561.5156

1.46881.4531

1.48441.5ooo1 .r312l. 5469l. 5625

1.5781l. 5625

l. 5781

1.5000

1.53121.5156

l. 59381.5625

l.62501.6094

1.64081,6250

l.6406

1.5312

1.5625l. 5469

l.57811 5938l.60941.62501.64061.6562

1.68751.6719

l. 7031

1 .2500

8777877277

6587

6772

Iin I"""""""""" """_""""" ~ " " " " " " _ _ _ _

""_"""""""~ """"_""""" " " " _ ~"""""""""" " _ " _ _"_""""""""""""" ""_""""____""""" ~ " " _ _ _"""""""""""_""_ _ _ _ _ _ _

7Y """""7 ""_"""""""_72 ""_"""__-"____87 """"" ""_"_ " _ _ " " _77 """""87 -'-- - - - - - - - - - - - - - - - - - - -72 _ _ _ _ _ _ _ _ _77 """"" " " " _ " _ _ _ _ _ " _87 """"" _"""_65 _ - _ _ _ - _ - - - _ _ _ - _ _ _ _ _ __ _ _ _ _ _ _ _72 _ ._ _ _ _ _ -_ _ _ _ _ _. _ _ _ _ _ _67 _ -__ _ -.---__ _ -_ _

79 """"" " " " " _ " " _ _ _ _ _72 """"" """"""_""87 """""""""" """_77 """"" "--""""___"87 """-_-- """"" _ _ _ _ _ _ _72 _ _ _ _ _ - _ _ - __ _ . _ _ _ _ _ __ _ _ _ _ _ _ _77 """"""""""87 """"" _ "" " " " "____72 """"" """""_ _ _ " _ _ _67 _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _87 """""""""" _ _ _ " _ _87 """""""""""""_9 """""""""" " " _ _ _77 """""""""" _ _ " _ _ _87 """""""""" "_""72 """""""""""""_77 """"" """__ _ " _ _ _ _ "87 """""""""" ""_"72 """""""""" "_""_67 _ _ _ _ _ _ _ _ - __ _ _ _ - _ _ _ __ _ _ _ _ _ _ _

72 _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _9 """"""""""_"""87 """"" """"" _ _ " _ _ _87 """""""""" """_7 """""""""" " _ _ _ _ _72 """""""""" " _ _ _ _ _87 """""""""" """_7 """"" _ " " " " " _ _ _ _ _ _65 . . . . . . . . . . . . . . . . . . . . _ _ _ _ _ _ _ _ _72 """""""""" " " _ _ _7Q _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _72 """""""""" " _ _ _ "87 """""""""" _""__77 """"_- """"" " _ " _ _87 """""""""" _ _ _ _ _ "72 - - -- - - - - - - - - - - - - - _ _ - - - _ _77 """""""""" "_""87 """""""""" " _ _ _ _ _ _65 _ _ _ _ _ - _ _ _ __ _ - _ - _ _ _ __ _ _ _ _ _ _ _72 _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _87 """""""""" """_79 """""""""" *"""

77 """""""""" " " _ _ _2 __"""" """"" """_87 """""""""""""_72 __"_""""""""""_"_77 """""""""" " " _ _ _87 " " " L " - """"" " " _ _ _65 _ _ _ _ _ - _ - _ -_ _ - _ - _ _ _ __ _ _ _ _ _ _ _72 """""""""" " " _ _ _84 """""""""" """_78 """"" """""" _ _ " "87 __"""_""""""_""___72 """""""""" " " _ _ _9 """""""""""_""87 """""""""" ""_"77 """""""""" " " _ _ _67 _ _ _ _ _ - _ _ _ __ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _87 """""""""" " " _ _ _72 ""_""""""""""""77 """"" """"" """_72 """""""""""""_

"_-_"""__""___ _ _ " "I _ _ _ _ _ " _

"_-"_""__"_"_

" _ _ _ _ _ _ _

""""_

-



--` ` , ,` ` ` ,` ` , ,` ,` ` , , , ,-` -` , ,` , ,` ,` , ,` ---



Thread size

in

1 .8125

1 .8125

1 .S1251 A1251 .8125

1.875

1.875

1.875

1.875l. 875

1.9375

1.9375

l. 9375

1.9375

2.000

2.0002.000

2.000

2.0002.000

2.0825

2.125

2.1252.1252.1252.125

2.18752.250

2.250

. 2.2502.250

2.2502.250

2.3125

2.3752.3752.3752.3752.375

2.4375

2.5002.5002.5002.5002.500

2.500

2.625

2.625

2.6252.625

2.6252.625

, 1.9375

-

rhreadape r

inch

-

6

8

12

2016

6

8

12

2016

6

8

12

2016

4.5

68

12

2016

16

6

128

2016

164.5

6

128

2016

16

6

128

2016

16

4

681216

204

68121620

468121620-

FED- STD- H28/2A

TABLE n . A . 1 -Tapdr i l l s izes, Unif ied screw threads,c lasses 1B and 28 -Continued-

k a i g -lat ion

-

U N

U N

U NU NU N

U NU NU NUNU N

U N

U N

U NU NU N

U N CU NU NU N

U NU N

UNS

U NU NU NU NU N

UNSU N CUNU NU NU NU N

U N S

U N

U NN

U NU N

UNS

U N CU NU NU NU N

U NU NU NU NU NU NU N

U N CU NU NU NU NU N-le .

T Classes 1B and 28 minor diameter,

a i n i m m

in

1.632

1.677

1.722

1.7581.745

1.695

1.740

1.7851 . N 71 .a21

l. 757

1 .802

1.847

1.8831.870

1.759

1 .8201.865

1.910

1.9321.946

1 .995

1.945

1.9902.0352 .O572.071

2.1202.080

2 .O702.1152.1602.1822.196

2.245

2.1952.2402.2852.3072.321

2.370

2.229

2.3202.3652.4102.432

2.4462.354

2.4452.4902,535

2.5712.557

2.4792.5702.6152.6602.6822.696

internal

Percent"of

thread

83.4

83.4

83.683.183.9

83.1

83.1

83.1

83.883.1

83.4

83.4

83.6

83.983.1

83.5

83.183.183.1

83.883.1

83.1

83.1

83.183.183.883.1

83.183.5

83.183.183.1

83.183.8

83.1

83.183.183.183.883.1

83.1

83.4

83.183.183.183.8

83.183.4

83.183.183.183.883.1

83.183.4

83.183.183.883.1

m a d s

Percent-

thread

in

1.663

1.702

1.740

1.7701.759

1.725

1.765

1.8031 .a211.832

1.788

1.827

1.865

1.8841.895

1.795

1.8501.890

1.928

1.9461.957

2.009

1.975

2.0152.0532.0712 .O82

. .1342.045

2.100

2.1782.140

2.1962.207

2.259

2. 2262.2652.3032.3212.332

2.384

2.267

2.3502.3902.4282.446

2.4572.392

2.4752.5152.5532.5712.582

2.5172.6002.6402.6782.6962.707

69.1

68.0

67 O

65.965.4

69.3

67.7

66.5

66.566.2

69.1

68.0

67.0

65.465, -

71.O

69.367.7

66.5

66.566.2

65.9

69.3

67.766.566.566.2

65.971.O

69.367.766.566.566.2

65.9

68.8

66.567.7

66.666.2

05.9

71.7

69.367.766.566.5

66.2

71.7

69.367.7

66.566.5

66.2

71.769.367.766.560.566.2

TD r i l l ek e

Tap dr i l l and percent of thread

in1 e2501.64061 .e5621 A7191 .m751.7188

1.75001.7344

1.7656

l. 70311.71881.75001.7812l. 79691 A125l. 8281

l. 76561.78121.79691.81251 .E438l. 85941 .a7501 .8906

1.78121 .S281. 1.84381 .S7501 . m 21.9219

1.95311.9375

2.O000

1.95311 .W3882.MHH)

2.08252.0312

2 .O625

2.12502.oooo2.03122.O6252.12502.15622.18752.1875

2.2500

2.18752.25002.28352.31252.3125

2.3750

2.25002.2188

2.31252.3750

2.43752.4082

2.43752.34382.37502.43752.50002.53122.56252.5625

2.50002.50252.62502.65622 .e8752.6875

%srcent-/

threadireeanhread,.eol evereize,f P e r n t -robablerobable1 1 /

87

_ _ _ _ _ _ _ _ _ __ _ _ _ _ _ _ _ _2__"""_""""""""9""""_""""""""_ _ _ _ _ _ _ _ _

87 """""""""""""""""""7""""__ _ _ " _ _ _ _

87 """ "-I """"" """_72 """""

_ _ _ _ _ _ _ _ __ _ _ _ _ _ _ _ __ _ _ _ _ _ _ _ _2" _ _ _ " _ _""""""""7" _ _ " _ _ _""""

79

!? I""""" """"" _"""""""""""" _ _ _ " "

a l _ _ _ " " _ _""_"_""""87 _ _ _ _ _ _ _ _ _ __ _ _ _ _ _ _ _ _2

" _ _ _ " _ _""""""""7 """"_"""""""" _ _ _ _ _ _ _ _ _77 """"""""""

_ _ _ _ _ _ _ _ __ _ _ _ _ _ _ _ __ _ _ _ _ _ _ _ _2"_"""

7679727787727772

77

7279

7787

9677

877776877787

9677

77

877785

9677

77

8777877787

96

77

87778777877796

77

_ _ _ _ _ _ _ _ __ _ _ _ _ _ _ _ __ _ _ _ _ _ _ _ _6"""_""""""""""7"_"""""""""""7"""_"""""""""7

_"7""_""""""""""





F E D - S T D - H Z B I Z A T H m 7747777 0001552 3 M-

~ ~

FED -STD -H28/2A

TA BL E II. A .1- Tap dril l sizes, Unified smew ttreads,classes 1B and 28 -Continued

Classes 18 and 28 minar diometer,

internal hreadsTap dr i l l and percenl of thread

' M a d s

inch nationper Desig- T

inLnum

il 1

2.6952.604

2.7402.7852.8072.821

2.7292.8202.8652.9102.9322.946

2.979

33 2 93.479

Thread slzaPerc t-

Threadhread Thread mean size Throcrd

1 /Perc nt-

1 /

oQ" Maximum a Dri ll size oversize, holel/Probablerobable Per c nt"

o t1 1in

2.8752.875

2.8752.875

2.8752.875

3.0003.0003.o003.0003.0003.000

3.250

5.5003.750

71.7

67.769.3

66.566.566.2

71.769.367.7

66.566.5

6 6 . 2

71.7

71.771.7

il 1

83.4 2.64283.1 2.725

83.1 2.80383.1 2.765

83.8 2.82183.1 2.832

4 U N6 U N

12 U N8 U N

20 U N16 UN

4 U N C6 U N8 U N

1 2 U N

20 U N16 U N

778777877796

2.62502.68752.75002.78122.81252.8125

2.7500 77 """""2.81252.8750

87 _ - _ _ _ - _ - _ _ _ _ - _ _ _ _ _2.9134 80

77 _"""."_"""_

2.93752.9375

Y6 . . . . . . . . . . . . . . . . . . . . _ _ _ _ _ _ _ _ _7 """"" """__

3.oooo 77 """""3.5000

.2500 77 """"""""""77 """"""""""" " _ _ _

" _ " " " " " _ _ _ _ _ _

""_"""""""""__"__ " _ _ _ _ _ _ _" _ _ _ _ _ _ _

-"-"""""_____" _ _ _ _ " _"1 100°/o of t h r e a d = 0 . 7 5 H ( l e e 2 0 . 2 . 3 ) .

TAB LE IC.A .2 -Top dr i l l s izes, Unif ied screw ihreads,class 38

ClassBminoriameter,internalhreads Taprlll andercent of threadTI I e r p t

Threa&

J/Percn t

Thread

1/ 1

Maximum o?Perc n/ Prob ble Probable Perc ent Y

D r i l l s ize O? over%ze, hole a tThreadw n s i z e T hr ead

Hlnimum-i n

0.0466

.o561

.O580

.O667

,0881

.O764

'.O797

.O849

,0894

.O970

.lo04

,1040

.1110

i n

.o80

,073

,073

,086

IO86

.09u

.o99

,112

,112

* 125

,125

.138

,138

52.9

i nO. 0465i n

.O469

.O550

.O595

.O625,0595

.o870,0700

.O730,0700,0730

,0781,0760

.O785,0810.O820.O810,0820,0860

. 860

.o935

.O890

.O938. 890

.O938,0935

.o960

. 980

.o995

.lo15

.lo15,1040

.lo65I 1049

.lo65,1040

.lo94Il l00,1110.1130.1110.1130,1160

0.0480i n

.O484

.OM5

.o610

.o610

. 640

.o687,0717

.O717,0747

,0747

.O779,0800,0804.O829.O839.O829.o839.O879

,0879.Oe10,0955.O958.o910

.W58* 0855

.o980

.lo03

,1038,1018

,1063I 1038* 1083* 1088

.lo83

.lo88a 1120,1126.1138.11M.1136,1156a l l e e

-

i n

0.051r

.062:

.063L

.O737

.O753

.O845

,0865

.O939

,0968

* 1062

,1079

.1140

0.0015i n

.O015

.O015,0015.O015,0015

,0017,0017

.O017,0017

.O017

.o019

.o019* 0019

.o019,0019

.W19,0019.o019

,0019.o020*0020*0020

.o020*0020

a0020.o020

,0023

. 023,0023

.O023,0023

.O023,0023

.O023I0023

.O026

.O026

.O028

.o026

.O026

.O026,0026

80

64

72

56

64

48

56

40

48

40

44

32

40

U N P

U N C

U N P

U N C

U N F

U N C

U N F

U N C

U N F

U N C

U N P

U N C

U N F

83 .

83.;

83.

83.:

83.:

83.:

83.1

8 3 . 4

83.5

83.4

83.3

83.8

83.1

8381

89677558

826956

6479

7785

766763787356

80715756

6885

6759

8379

65

72

807163

8478706967

8382

6877

7471

c6750

"53.0 #50 .

52.7

#51

1#49

74655150

6170

Bo52

7176

65

586355

7872

63e4

805575

Bo69

73

'X40

57.9

, #37#3857.9 ' #37

#36

x3 7#36

59.1 y35#34#3 3#34

59.7 ' #33X32

See footnotes at end of table.-

20



--` ` , ,` ` ` ,` ` , ,` ,` ` , , , ,-` -

` , ,` , ,` ,` , ,` ---



F E D - S T D - H Z B / ZA H m 7777777 0003553 5

FED-STD- H28/2A

TABLE I f . A . 2 -Top dr il l sizes, Unified screw threads, class 38-cont inu ed

T Class 38minor diameter, internal threads Tap d ril l and percent o f threadrhread!

inchper DeSig -

nationThread siz 1ercent-

1

Threado f

83.¿

83.1

83.1

83 E

83.1

84.1

83.8

83.1

84.1

83.8

83.8

83.8

84.1

83.0

82.:

83.E

83.1

84.183.1

83.8

83.5

83.1

83 Y

83 o82.5

83.1

83.183.883.184.1

83.8

83.B

83.1

83.8

83.9

84.1

83 O82.5

Percent"

Threadof

1' e r c s n f

1

Thread

a tr i l l s lzelinimum

in.13M

.134C

. ~ a

.186U

,1710

.1770

.1820

.1960

.2110

.2160

,2520

* 2580

.2670

,2740

.279C

,3070

.S210

.3300

.3410

.3360

.3600

.3740

.3830

.3Y90

.4040

.4100

.4320

.4170

.4610,4460

.4660

,4720

.4950

.5020

.N80

.S170

,5240.5290

Maximum

i l l

.164

.164

32

36

in,1389

.1416

.1555

.I641

.M07

.la57

.la95

.ZOG7

.21YO

.222Y

,2630

.2680

.2754

.2807

,2847

,3182

.3297

.3426

.a372

.346Y

,3717

.3800

.391G

.4051

,4094

.4223

.4284

.4419

.4537

.4676

.471Y

.4843

,5040

.5106

.S162

,5244

.S301

.S344

61.8

62.1

63.7

63.8

05 .2

65.3

65.3

66.7

66.8

66.8

68.6

6 8 . 5

6 8 . 5

6 8 . 5

6 8 . 5

70.0

6Y.7

6Y .869.8

BY. 2

i o .

70.8

70.7

69.8

69.2

71.8

71.771.6

69.871.3

6Y . 2

72.2

72.1

71.9

71.3

70.4

69.869.2

69

6578

65

857075

68i 0

83817671

82i Y

07i 2

8478

G Ïi 3

X47Gï oG7

83i Y75'i2

GY71

80677771

777185

i 27Y

8675i 7

77

78

777380

787Y

'i7

8486

77757072

8372

77

8072i 8

7277

7677

87727787787287787877

in.O029.o029

.OOZY

.O029

.O032

.O032,0032.O032

,0032.o032

,0032.o032

.O032

.m35. 035

.00:1*5

.o035

.OOB.Ï

.00:35

. o035

.ao:í.;

. o035

.003.Ï

.00:35

.o033

.00:1x.00:3x

.O038

. 03 8,0038

. 03 8,0038.O038.O038.O038

.O038

*0038.O041

.o041

.O041.O041

.o041

.O041,0042

.o042

,0044

.O044

.o044

.o044

.o044

.o045

.O046

.O046

.O046

.O046

.O046

.O046

.O046

.O046

.O046

.O047,0047,0047

.O047

.O047

.O048,0047

.O048

.O048

.O048,0048.O048.O048.o048.O048

.004Y,004Y"

in.138Y

. .1389.1a34.1435

,1472,1502,1527.1592.1572.l.ï91,1602.1622.1642

.1754,1766. I &O9,1885

.1a33

.18%

.1a85.1a55

. lelo1886

,1925

* l9Y8,2028.2048.206Y.ZU78.z0g3

.2168

,2226,2226

.2248

,2608.2651.2608,2651.2701

.a761

.2701

.2811,2852

.2854

.316Y

.3274

.3204

,3384.3434.3483

,3626.3640, 3 Ï :I6

,3906.3&:6

.3952

. 4086

.4086,4108

.4177

.426G,4266.4422.4578

.46Y3,4736

.4736

.4892

. W48

,5110,5048

,5204. 204,5251.5312.5361

.18O.r,

62705757

7974G964617573

6468

75736660777066

596875

62B8

7773

in

.1360

.1360

.1405

.1406

,1440.1470.14Y5

.1540,1520

,1562,1570

,1610.15YO

.IÏlY

. l i30-1 i70.1 OO. i 70.la00

.la50,1820

.1820

.la75

.l890

.m n

.ln60

. lYOO,2010. 208 1.2040. 2095,2130.2188.2188.2210

.2610

.2570

.2570

.2610. 660

.L660

.2720

.2770,2810

.2812

.3125,3160. 3230.3320.93YO.3438

.35Y4

.3580

.3750

.8770

.3YOG

.S860

,4040.4040

,4062

.4130

.4219,4219.a75.4531

,4688,4646

.-I688

. 4844

. 00 0

. 00 0

.S062

.S156

,5203,5156

. 263

.S312

U N C

U N P

24 U N C

.1YO U N P2

.?16 24 U N C

.216 28 U N F

,210 32 U N E F

.280 20 U N C6670

656372596762

. -

.250

.250

28

32

UNI:

LiNEY

.3125

.3125

,3125

,3125

.3125

I 8

20

24

28

32

U N C

U N

UNI.'

U N

UNE1;

.375 16 U N C

.375

.375

.37B

.375

20242832

U NUN1;

U N E FLrN

.c375

.c375

.4375

.4375

.4375

14

16

20

28

32

U N C

U N

UNI;

U N E F

U N

817Y

6Y71

. 7265

627166

.500 12 U N S 76

7368

6571

6566

.m

.w o. 00

.500

.500

12 i U N C

16 I U N

18 ' UNI?

20 I U N

24 U N E F

.S625

.5625

.S625

.S625

.S25

.S625

.S625

826871

28 U N32 U N

See footnotes st end of table.

,



--``,,```,``,,`,``,,,,-`-`,,`,,`,`,,`---



F E D - S T D - H 2 8 / 2 A T H m 7777777 0003554 7 W~ ~ ~

FED-STD-H28/2A

TABLE II. A .2 -Tap dri l l sizes, Unified screw threads,class 38 continued

Class 38 rninor diameter,internai threads Tap dr i l l and percenr ot Ihmad

Threadsize Desig-hmodo '

Minimum of Moxirnurn ofp,"Eh nationercent' 1 / P e r c e n f /

ThreadDr i l l s i ze

Thread

i n

.625

.625

.625,625

,625

,625

.625,625

.687,'687,,687,,687)

.687!

.687r

.750

.750

.750,750.750,750

.812!

.812.,812:.812!

.a75

.a75

.875

.875

.875

.a75,875

.937!,937:'937t,9371,9375

1.o00

1.o00

1 o00. 1.OOo

1.o001.o00

1 o00

mi

1.0828

1.06251.06251.08251 O6251O625

1.125

1.125l.25

1.1251.125

1.1251.125

1 18751.1875

l.875l.875

1.1875l.875

1.2501.250

1.2501.250

1.2501.250

1.250

11121618

20

24

2832

121620242832

1012

2016

2832

1216202832

912

14

2016

2832

121620

3228

8

12

14

2016

2832

8

1216182028

7

812

1816

2028

81216182028

7

128

16

20I8

28

U NCUNU N

U N P

UN

UNE1

UNU N

UNU N

UNEFU N

U NU N

U N CUN

UNEFU N F

U NU N

U NU N

UNEFU NU N

UN CU N

U N F

UNEFU N

U NU N

U NU N

J N E FU NU N

U N C

U N F

U N S

J N E FU N

U NU N

UN

U N

I N E FU N

U NU N

U N C

U NU N FU N

I N E F

U NU N

U NU NU NI N E FU NU N

UN C

U N FU N

INEFU N

U NU N

-See footnotesa t end of !able.

in

.5354

.S271

,5571,5654

.571l

.580

.5861

.5Y I I

.597l

.62@

.6421

.633(

.G54(

.64HI

.642(

.660(

.G82(

.G%(

.711(

.716(

.722(* 7454.758(.774(* 779(

.75M

.785C

.798C

.821C

.807c

.836C

.a410

.a700

.847C

.8YW

.ama

.m40

.8650

.91o0

.W30

.9610

.9460

. 9660

.932a

,9270

.e726

.99501m20

1O2401.o080

,9700

1O350* 9800

1O5701.0650

1O7101.om0

1 O5201O9701.1200l.270l.3301.1480

1 o9501.1150l.600l.8201.1ma

1.21101.1880

83.I

83.83.

83.

83 .

83.

84.83.<

83.1

83.!83.

84.83.I82.1

83.

83.183. '

83.:84.'83.1

83.(

83.$83.1

82.!83.t

83.183.1

83.(83.t83.184. I83.1

83.f83.183.b

82.5

83.1

83.1

83.a

83.a83.8

84.183.1

83.8

83.4

83.183.6

83.983.8

83.0

83.5

83.183.1

83.183.8

83.184.1

83 B83.483.183.8

83 O83.9

83.583.183.1

83.183.8

83.184.1

O181

1

1

18

61D1D5

I

l3I

l3

I

i

1L

I

i

i

ll,

I

i n

.5391

.546:

.%G:

.573(

,678;

. 586$

.592t

.89Bt

. GO8 !

.628j

.64Y4

.641z

.6594

.6551

.654L. i O i

.690E

.7035

.721S

.7176

* 7329,7533,7661,7801.7844

.î681

.7952

. W 8

,8158.a287.S426.8469

.a783

.a575

.ao12

. go51

.9094

.a797

,9198

,9315,9408

.9676

.9537

.O719

.9422

,98231 o033

1O1621O105

1O301

.Y875

1O4481 .O047

l.7301 o658

1.07871O926

1 o672l.0731.1283l.3551.1412l.851

1.11251.1297

l.9081.1698

1.1980l.0371.2176

72.'72*:72..72.:

71.:

i o . .

6Y .I6Y .:

73.(71.,70.169.169.:

73.!72.i73.:

G9 . I71.?

GY .I

73.172.s71.3

6Y . 269.E

73.774.1

73.5

72.971.369.869.2

73.972.Y71.3

69.269 .8

74.1

74.1

73.872.971.389.869.2

72.!

74.1

72.974.1

72.171.369.8

74.1

74.174.1

72.Y72.1

69.871.3

74.174.172 Y72.1

69.871.3

74.174.1

72.974.1

72.171.369.8

i n.531'.546.562,

. 5G8

.562,

.S78,578

.i5821,8821

,5931

.5Y31,6251

.640(

.6401

.Ci491

.I3561

.640(

.687!

.G56:

,7031,708;,7181

. ,728:.75M,7656.777t.7812

.765f

.7811

.7962,8024.812L.8281.S366,8436

.S438

* 8906.a957.9062

.a594* 8750.Cl062.9219.o274,9375

.9645

.9531

.W388

.cl219

.9274* 9375

1 oooo.9688

1oooo1 o1561.0312

,9688.Y844

1.oooo1O312

1 o6251 o825

.a750

11

111.1,1.1.1,

,0781.O938

,0625,0838.1250,1250.1406,1516

,0938,1250I 1562I 1875,1875I 2031,2108

Percenf Probable Probable Pcrcenl -Th rea d m a n size Thread

7!

7;7:

8;717:8 ;

917t

7i

8i7

8i71

8175

848577

8s72

77

787772

7775

8776

847877

8372

77

87

7277

9077

877787

84787772

7777

8387

778777877267

8478

8777

8777

7267

8777

8777

7277

84778777

7287

85-

,536:i l l

,5511

.S674

.5671

.583(-573t

.587r

.598 i

.587i

.598i

.630(

.645€

.645€

.6612

.6456,6611.6Y25.7082

.7239

.713@

.7334

.7552

.7708.7828.7864

.7708

.7864

.ao21

.8178,8076

,8420.a335

,8493

.a493

. m 7,8965.9017,9122

.m53, 8 8 0 8

.9122

.9279.9437,9335

.9594,9709.9753

.m79

.9335* 9437

1O089.9753

1 o0691.02261O383

.I3750

1.0089.o911

1O3831.o899

.583!

.654e

"""_.

- - - - - - -.

- - - - - - -.- - - - - - -.- - - - - - - .- - - - -.- - - - - - -.""""- - - - - - .""""""""""""""""""""

,

22

.ided by IHS Sold to:HOLTEC INTERNATIONAL, W0847024Not for Resale,2010/2/2 15:49:11 GMTeproduction or networking permitted without license from IHS



-F E D - S T D - H 2 8/ 2A H m 7777777 0003555 7 m

I I I Class 38 minor diameter,infemaihreads I Tap d r i l l andercent of tiwead

I I I Thread I;Il

1.3125

1.3125

1.31251.3125

1.31251.3125

1.375

1.375

1.375

1.3791.375

1.3751.375

1.4375

1.4375

1.43751.4375I .4375

1 4375

1.500

1.500

1.5001.5001.5001.5001.500

1.5625

1.5625

1.56251.56251.56251.5625

1.625

1.025

1.6251.0251.0251.625

1 I3875

1 L38751.08751 I38751A8751 íI875

1.750

1.750

i.50

l .7501.7501.750

1 8125

1 A125

1 81251.81251 A125

1 875l . 75

1.8751.875

l .875

1.9375

1.9375

1.93751.93751.9375

1.4q75

8

1612

182028

6

8

1216

2018

28

6

8

1210182028

6

8

1210

2018

28

0

8

12161820

6

8

12101820

0

128

101820

5

0

8

121620

0

8

12

2010

68

12

2 010

0

8

121020

L'N

U N

U N E FU N

U NU N

I:N C

UN

U N P

U N E VU N

U NU N

U N

U N

U NU N

U N E F

U NU N

U N C

U N

U N F

U N E FU N

U NU N

U NU N

U NU N

UN E FU N

U N

U N

U NU N

U N E FU N

U N

U NU NU N

U N E FU N

U N C

U N

U N

U NU NU N

U N

U N

U NU NU N

U NU NU NU NU N

U N

U N

U NU NU N"

ee footnotea at end of table..

il l

l . 1770

1 .2220

l . 5201.2450

1.2580l .2740

l . 1950

1.2400

1 30701.31801.3210l . 360

1 2970

1 3020

1 34701.37001.37701 .M30l .3990

1.3200

l . 650

1.41001.43201.44001.44601.4610

1.3820

1,4270

1.4720

l .50201.4950

l .S080

1.4450

1.4900

l .5350l .5570l .5650l . S710

1 5070

l .55201 50701 02001 L3270l .6330

1 5340

1 57W

1 m50

1 .66001.0820l .0900

1 I3320

1.6770

l . 220

1.75801.7450

1.09501.74001.78501 W701 a210

l . 570

l . 02 0

1 .M70

1.88301 .a700

1 2 a o

83..I

83.183.6

83.883.983.0

83.1

83.1

83.183.883.183.184.1

83.4

83.4

83.683.183.883.983 O

83.1

83.1

83.883.1

83.183.184.1

83.4

83.4

83.683.183.883.9

83.1

83.1

83.183.883.183.1

83.4

83.483.683.183.883.0

83.1

83.1

83.1

83.183.883.1

83.4

83.4

83 B

83.883.1

83.183.1

83.883.1

83.1

83.4

83.4

83.083.183.9

,

i n

l . 1922

l . 323l .2533l .2605

1 2801l . 2662

1.2146

1.2547

l . 29481.31.581.3230l . 32871.3426

1.2771

1.3172

1.3573l .37831.38551.39121.4051

1.3396

l .3797

1.41981.44081.44801.45371.4070

1.4021

l . 422

1.48231 ,5033l .51051.5102

l .4040

l .5047

1 54481 5658l .57301.5787 '

-1

1

1

111

.5271

.I3073

.5072

,0283

.0412

.5575

.5890

.I3297

.I3908

.0098

.7037

.e355

1.0521

1 6922 I1.73231.7533

1.70621.7146l .75471.7948

l .82871 8158

1.7771

1 23172

1 a573

1.89121 a783

74.1

32.5 m m9.81'741.3lx2.11%2.9144.1 {i2

i n

74.1

74.1

i:&

1?414.172.9 14fa72.1 1%71.3 1%09.8 34 mm

I74.1 I 11%

74.1 {i274.1 1 1 1 472.9

35.5 m m0.81*'41.31%2.11%

74.1

1%1.31% 72.11%2.9lia%

09.8 37mm

74.1

74.1

l * ,

{i274.1 11'472.9

1 ' 7 41.31%2.11%

74.1

74.1

74.1

74.1 1%72.9 lllA71.3 l"4

74.1

1491.3

1%2.9

74.1

i&i4.1 12'4

:::i74.1

1'341.311'42.912'4

74.1

74.1 {i:$74.1 12'472.9 l'x71.3 l',A

l . 1719

l . 18751.25001.2188

1.2500

1.2795

l . 1875l . 031l. 3441.25001.28121.31251.31251.3281l . 380

l . 056l . 9091.31251.3438

l .Y7501.3750

1.39081.3970

l .32811.3125

1.35941.37501.4082l . 375l . 3751,45311.4507

1.39081.42101,4375

1.50001.4088

1.50001.5156

1.45311.48441.5oOo1.5312l . 025l .50251.5781

1.5000

1 M251.5156

1.59381.62501.6250

i n

1 2658

1:t1408

1.54081,5312

1.50251.57811.0094

1 m 21A8751.7031

1 e250

1 e2501 e4001 A7191.08751.71881.7500

11.70311.7500

1 81251.7812

1 8281

l .705el .79091.81251A4381 8WO1 . 8 W

L

i ll il l

87

"""_""""" """""

7 _"""""""" """""7

_""""""""__""""77 """"" """""""_"87

_ _ _ _ _ _ _ _ __ _ _ _ _ _ _ _ __ _ _ _ _ _ _ _ _1_ _ _ _ _ _ _ _ __ _ _ _ _ _ _ _ _____ _ .___2""""_""""""""

87

" " _ _ _ _ _""""""""8_ _ _ _ _ _ _ _ __ _ _ _ _ _ _ _ __ _ _ _ _ _ _ _ _2""""_""""""""7""""_""""""""7"""_"""""7""""_""""""""7_ _ _ _ _ _ _ _ __ _ _ _ _ _ _ _ __ _ _ _ _ _ _ _ _7"_""__""""""""9""_""""""""""

79 """""""""""""_87 """""""""" """_87 """""""""" "_""7

_ _ _ _ _ _ _ _ __ _ _ _ _ _ _ _ __ _ _ _ _ _ _ _ _2 _ _ _ _ _ _ _ _ __ _ _ _ _ _ _ _ __ _ _ _ _ _ _ _ _0

""""_""""""""7"_"""""""""""7

""""_""""""""

87 """""""""" """_79 """""""""" """_87 __"""" """"""""_77 """""""""""""_87 """""""""""""_77 """""""""""""""""""7

.""""

""""_""""""""3_ _ _ _ _ _ _ _ __ _ _ _ _ _ _ _ __ _ _ _ _ _ _ _ _2""_""

79 """""""""" """_87 """""""""""_""77 """""""""""_""87 """""""""""""_77 """""""""" _"""87 """""""""" "_""72 _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ . _ _ __ _ _ _ _ _ _ _79 """""""""""""_87 """_"_ """"""""_77 """""""""""""_87 """"""""""_"""87 """"""""""_"""

7 """""""""""_""72 _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _87 . . . . . . . . . . . . . . . . . . . . _ _ _ _ _ _ _ _ _77 """""""""""_""

9 """"" """"""""_87 _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _77 """""""""" "_""87 """"" """"""""-72 _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _84 """""""""" _"""78 """""""""" """-87 """""""""" """-79 _"_""" """"" _"""87 "_"""_ """"" _"""77 "__""" ""_"""""""87 ""_"_" """"" _"""77 """"" """"""""-72 _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _87 """_"""""""""""79 _____"""""""- """"-87 """""""""""""_77 """""""""""""_87 """""""""""_""

72 . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7 """"" """"""""-

79 """""""""" """-77 """""""""" ""---87 """""""""" ""---77 _ _ _ _ " _ " _ """"" ""---72 _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ -79 " " _ _ _ " _ """""""""-87 _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _7 7 _____""""""""""""87 " " _ _ _ _ _ _ """_""""""77 """""""""" """-72 _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ r _ _ _ _ _ _ _ _ _ _ _ _ _



--` ` , ,` ` ` ,` ` , ,` ,` ` , , , ,-` -` ,

,̀ , ,` ,` , ,` ---



F E D - S T D - H Z B / Z A T H m 9 9 9 7 7 7 7 0003556 O m

FED-STD-H28/2A

Thread s iz

2.1252.1252.125

2.1252,125

2.187!

2.250

2.2502.250

2.250.2.250'2.250

2.3125

2.3752.375

2.3752.375

2.375

2,4375

2.500

2.500

2.5002.500

2.5002.500

2.6252 6252.6252.0252.6252.025

2.7502.750

2.7502.750

2.7502.750

2.8752.8752.8752.8752.8752.875

3.0003.0003.000

3 .0003.000

3.000

3.250

3.500

3.750

'hrecd!

i n chPer

-4.56812162016

6

128

2016

16

4.5

6

128

2016

16

6812

2016

10

4

6812

2016

4

68121620

468121620

64

8121620

4

86

12

2016

4

4

4

Dasig -nation

U N CU NU NU N

U NU N

U N S

U NUN

U NU N

U N

U N S

U N C

U NU NU NU NU N

U N S

U NU NU NU NU N

UN S

U N C

UNU NUNU NU N

U N

U NU NU N

U NU N

U N CU NU NU NU NU N

U N

U NU N

U NU NU N

U N CU N

U NU N

U NU N

U NC

U NC

U NC

TABLE I I .A .2 - Tap dril l sizes, Unif i l

Clase 38minor diameter, internal hreads ibiinlrnum

1.759ain

1 8200l.8 6 s1.91OC1 .932cl. 946C1.9950

1.94501.99002.035C2.057a2.0710

2.1200

2 . m a

2.0700'2.11502.1"2.18202.1960

2,2450

2.19502.24002 28502.30702.3210

2.3700

2.2290

2.32002.36502.41002,43202.4460

2.3540

2.4450

2.53502.4900

2.57102.5570

2.47902.57002.61502.68002.68202.6960

2 W O2.68502 *74002.78502.80702.8210

2.82002.7290

2.86502.91002.93202.9460

2 I9790

3.2290

3.4790

Percent

T hreadof

1

83.583.183.183.183.E

83.183.1

83.183.183.1

83.1

83.1

83.5

83.1

83.183.1

83.183.8

83.1

83.183.183.1

83.183.8

83.1

83.4

83.183.1

83.183.883.1

83.483.183.1

83.883.1

83.F

83.483.183.183.183.883.1

83.483.183.183.183.883.1

83.8

83.4

83.183.1

83.883.1

83.1

83.4

83.4

83.4

-/ iOO% of thread = 0 . 7 5 H ( s e e 20.2.3).

~

: ~.

Maximum

T1.78811.839f1 .a7911.919Il. 940I

2.003:l. 953:

2.004i1.964f

2.044t

2.07872.065t

2 1288

2.03612.08882,1297

2.190e2.2037

2.2533

2.21462.25472.29482.31582.3287

2.3783

2.25942.33962.37972.41982.44082.4537

2.38442.4646

2.54482.5047

2.56582.5787

2.50842.5896

2.66982.6297

2.69082.7037

2.63442.71462.75472.79482.81582 .8287

2.75942 .a962.87972.91982.94082.8537

3 .o094

3,2594

3.5094

in

2.1698

Percent

Threado f

Ir

74.174.174.174.172.971.372.9

74.174.1

72.974.1

71.3

72 9

74.1

74.1

74.174.1

71.372.9

72.9

74.174.174.172.971.3

72.9

74.1

74.174.1

74.172.971.3

74.1

74.174.1

72.Y74.1

71.3

74.174.174.1'74.172.971.3

74.1

74.174.1

72.974.1

71.3

74.174.174.174.172.971.3

74.1

74.1

74.1

%

screw threads, class 38 continued

Tap dr i l l and percent of thread

Dril l size

in1.7812

l.8750l. 8281

l. 90621.9375

2.oooo1 .Y531

2.oooo1 .O631

2.03122 I06252.0625

2.1250

2.oooo2.03122.0625

2.15022.1250

2.18752.1875

2.2500

2.1875

2.28352.2500

2.31252.3125

2.3750

2.21882.25002.3125

2.40622.3750

2.43752.4375

2.37502.3438

2.43752.5000

2.56252.5312

2.5625

2.50002.54252.6250

2.68752.6562

2.6875

2.62502.68752.7500

2.81252.8125

2.75002.81252.8750

2.93752.9134

2.Y375

3.oooo

3.2600

3 . m

2.7812

*

24

.

.

-_

1Perœnf

ofThread

76

777Y

87777277

7877877796

77

8776877787'7'796

77

877785

Y677

77

87

8777

7787

Y677

87778777

7787

96

7787

8777

7796

778777877796

7787

8077

7796

77

77

77

mean Thread

in In"""""""""""."_ _ _ _" _ " _ " " """"" _ _ _ _ " _ _"""""""""" _ _ _ _ _ _ """"""""" "_._"""" _"""""__"""_-""" """"" ""_"

"_"""_ _ _ " " _ _ _.__ -""""""""____""____"_"_""""""_"""_."""". ___"""""_"_".""."" """"" " " _ _ """"""""""""_."""_" "_"""""_"___."-""" """"" """_

" _ " " " " _ _ _ _ " "__"""" " " _ _ " ___"""" """_"_ " " " " " " _ _ _ _ "" _ " " " " _ _ _ _ _ _ _ _

""""" _ " _ _ _ _ _""""" _ _ " " """""" " _ _ _ " _""-"_"""-""__"""_"..""" "".""""_ _ _ _ _ _" _ " _ _ _ " _ _ " " " _ """"_""-"" """"" _ _ _ _ _ _ _ _

""""_ ___"""""_""_"""_ " _ _ " " _ _ _ " _ _ " _ _""""- """"" """__ _ " " " _ " _ " " " " _ _ _ _ _ _ _ _""""- """--"___""__"""~"""" _ _ _ " "

""""- """"" _ " _ _ _ _ _"_ """ """"" _"""_""""_ """"" _""__""""_ """"" _ " _ _ _ _" _ " " _ " _ _ _ " " " "_"""- _ _ " " " " _ _ _ ~ " _ " _ _ _ _ _ _ _ _""""_ """"" _ _ _ _ _ _ _ __ _ " " " _ """"" _ " " _ __ _ _ " _ _ _ _ _ _ _ _ _ " " _ " _ _ " _ _ _""""_ .""""""_ _ _ "_".""" _ _ _ " " " _"""_" " " _ " " " " _ _ _ " _" _ " _ " _ _ _ _ _ " " " _ " _ _ " _ _"_ " _"" """"_

""""" _ _ " " """""""""- " _ _ " " _-_"""""_""_"___"_"""""- " _ _ " " " " _ " _ _ """""" _"""

"

"""-_- ""_""_ "_"""""".__"_""" ""__"_""""""__""_ _ _ " _ " "" _ " _ _ _ _ "__""" _ _ " _ _ _ _ _" _ " _ _ _ " " " " " " _ _ " " _ __ _ _ _ " " _ _"_""" "_"""""""_ """"" """__

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APPEYTDIX B

D E S I G N OP UNIRD S W HREADS

40. Scope. Thisappendixprovidesguidelines which my be used in he

design of unified screw threads for hreaded parts. I t is not a mandatory partof thestandard. The informationcontainedherein is intended orguidanceonly. I t supplements nformationcontained i n Appendix B of ADTSI 31.1-1982.

50. General.."0.1 Introductio n. ngeneral, aqy given problem in hr eaddesign may ke

susce ptib le to severa l more or less satis facto ry solut ions based on the prelim-

inary sel ect ion of certa in elem ents of the design and the proper adjustment ofthe otherelements. In ot he r words, threaddesign is t o a large extentempiri-cal and is par t ia l ly based on previous experience with similar designs and thejudgmnt of thedesigner.Accordingly, it is notpracticable opresent adef in i te system of approach to th e de si gn of .a threaded assemb1,y but merely t opresent a discussion of various design factors.

50.2"acto r relat ionships . The int e rr el at ion of leng th of engagement,minimum major d i e t e r of th e ex te rn al hre ad , rmximum minor diameter of theinternal thread, and th e st reng th of the assembled thread needs t o be under-stood an d car efu lly con sid ere d in ord er to produce t he optimum design of aspecial hread. I t is noteconomical t o use e i ther a length of thr ead enm e-ment which is longer than required or short er than that which w i l l develop the

full strength of theext ern all y hre ade d member. Other fa ct or s, such ascont rol of tap breakage, proper seating of a threaded part on a shoulder, theprevention of cross threading, conditio ns of load ing when t he assembled pa rt sare no t concentric, a n d possible collapse of a hollow externally threadedmember, require careful analysis and adjustment of the design with respect t oselection of thediaxeter-pitchcombination, he class of thread, lengt,h ofe n r n m e n t , and major and minor diamter tolerances.

50.7 Thread f i t considerations. A clo se itt ing hre ad assemblyunder somecondi tio ns may f a i l , whereas the cause of failure m a y be eliminated by provid-ing a looser f i t . A cap screw that sea ts onl y on one s i d e of the beari ng sur-face under the head. m a y breakoff when the screw is ti&tened. When a screwhas a large bearing surface under th e head ,o r when t he head must be square with

a proje ctin g pin, suffi cient pitch diameter clearance m u s t be provided t o a l lowfor any outrof-squareness of the screw axis with the bearing surface under th ehead.Thus, as large a pitchdiamter olerance as possible, ogetherwithpraviding proper tolerances on squareness of face with the thread axis whereseating is required, mqy am id th e ne ce ss iw Tor specifying R heat treatedbolt,.



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F E D - S T D - H Z B / Z A T H 9 7777777 0003567 5 W

50.4 Standardhreads.with 4.1 . Informtion ona p p e a r s i n 5.1 and 5.2.

Use of standard threads is required n accordancepreferred sizes and clm se s for special threadsWhenever prac tic ab le, len gth s ofengagernent for

coahe , f i ne , 4 , 6 and 8 thre ad seri es sho uld be between 5 pitches and 1 1/2diameters; for a l l other series they should be between 5 and 15 pitches.Application of these princip les w i l l help keep costs of manufacture and gagingt o a minimum.

60. Eccentricitv of assemblv and cross threading.

Note: Table 6 of ANSI B1 .I-1982 inclu des abl es of 0.375H, 0.7% and H.

I n assembly and use, the combined tolerance s and al l m k c e s on both m t i n gpa r t s should not al lm threads t o d i s e n e onone side when assembly iseccentric. The axis of the nte rnal hrea d can be displaced radially fromcoincidence with the axis

ofthe ex te rn al th read by an amount; equal

t othe sum

of thepitchdiameter olerances a n d theallowance. This r a d i a l displacementmay be suf f ic ient s o that the f l a v l k contact is entirely on one side and on theopposite s i d e the c res t of the external thread will be in li ne with the c res tof the internal thread with the fo ll m in re su lt s when the screw is constrainedi n such a position i n a t appd ho le : ( 1 $ Tkiere w i l l be danger of crossing thethreads in s tar t ing, and (2) the screw may pu l l o u t of the hole when tens ion isexerted n t h i s constrainedposition. Theminimum amount of overlap isarbi t ra ry a n d controversial, but the following general rule can be used in l ie uofmore specific data:

As the f i rs t st ep to as su re th e minimum safe overlap on both s id es when theassembly is concentri c, he dif fgren ce between the minimum mjor dimeter ofthe

externalthread and the maximum minor diameter

ofthe internal thread

should notbe less than wice he addendum of the external thread (0.75H).Otherwise stated, he sum of the major-diameter toleran ce and allm an ce , if

amy, of the externa l thread and the minor-diameter tolerance of th e i n t e rna lthread s h o u l d not be gre ate r tha n 4/7 the addendum of the external thread,0.5II. This prov id es or a.minimum of 50 percent hre ad engagement. As thesecond step, to assu re the mini m safe ove rlap onone sid e when th e assemblyis ecc entr ic, the diff ere nce between the m a x i m u m p i t ch d i amte r of the in terna lthread and the minimum pitch diameter of the external thread should not begreater han hebasic hreadhei&t (0.625H). Otherwise stated, the sumofthe pitch-diameter olerances of both threads and theallowance, if amy, shouldnotbegreater han hebasic hreadhei@ t (0.625H). This pro vide s or anecc en tri c assembly conditi on equal t o haI f the basic thread hei&t (0.3125H)

and zero minimum overlap on one side. If the resu l ts from t h e limits of sizesel ec ted vi ola te the above rules , the tole ran ces sho uld be reduced by using aclo se r cla ss of tole ranc e, assuming tole ran ces con sist ent with manufacturingposs ib i l i t y , or a coarser pitch should be used to in cr ea se th e amount ofoverlap . The major-diameter to le ranc e of theexternall hreador minor-diametertolerance of the interna l thread should nah be less than the pitch-diametertolerance of the respect iv e hread o mintain hread form.Also, it, should benoted tha t , i f the tol erance on th e minor diameter of the internal thread mustnecessarily be large, the major diameter of the exbernall thread m u s t be heldc lo se t o t h e m a x i m major diameter and vice versa.

75




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F E D - S T D - H 2 8 / 2A H W 7777777 0003567 7 W

FED-STD-H28/24

TABLE 11.8.1

CHARACTERISTIC

Tensile Stress Area

Shearareatinternal hreads(Min material ext and ¡nthreadsl

Sheur area,internaI threads(Simplified:far dequa to ar

greater than0.250 inch)

Shear area,external threads.(Min material extand¡nt threads)

Sheararea,external threads(Simplified)

Shear arealextemal threads(Bask su e ext and nt threads)

Shear area,combined fallure

Shear stress area ratio

Material strength ratio

:ORMULAS FOR SCREW THREAD STRENGTH FACTORS

FORMULA.

As,,=3.1416 % b s c TLE

Asmin "3.1416 n L E Dlmax[& i-0.57735 d2min-Dimax

( 1AS,mn 3.1416Dimax

ASa=3.1416d2bsc-gLE

Asmax =3.1416Dlbsc--LE4 ( d k

Aqmax=3.1416 Dlbsc $L E

ASs3.1416 O, b s c 2E

- Foimula(6ajor(6b- Formula (2a)or (2;

Notation: d = major diameter, external thread (was Ds)

d= pitch dlameter, external thread (was Es)

DI =minor diameter. Internal thread (was Kn)

De= pitch iameter, internal thread (was,

es =allowance, external thread (was G)

L E =length of thread engagment (was Le)

n =number of threads per inch

UTSn=ultimate tensile strength of internally threaded part

UTS, =ultimate tensile strength of externally threaded part

T~,T~~,TDI,TD~,=oleranceon d,d~,D~,D~respectlvely

- .1875H =half external thread addpndumH16

bsc,max,min =modifiers denoting basic,maximum and mlnlmum

(tabulated inTable 60f ANS I B l.1-1982)

values,wspectively

3EFERENCEPARAGRAPH

70.I

70.1

70.2

70.2

70.4

70.2

70.2

70.4

70.3

70.3

70.5

70.7.5

70.7.5



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` , ,

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FORMULPNUMBER

FED-STD- H28/2A

TABLE II.8.2 FORMULAS FOR SCREW THREAD DESIGN

CHARACTERISTIC

Tensile stress, externally threadedpart- ure tension

Combined tensilesttess,externollythreaded part

Length of engagement based uponcombined shear ailure of externaland internal threads

Length of engagemant based uponshear of external thread

Lertgth of engagement awd upondeveloping ful l tensile strength of

external thread with threads atbasic size-usedwith(l6)

Length of engagement based uponshear of internal thread

FORMULA

S + = FA from(la)or(lb)

s;=s:ts,-2

With S+F

0.78541(d,mit1)~ d a

SC J-

S, = T dl min0.1S63k1min)4 - hii]

-1

L E =4A t from (la) or(lb )

3.1416 de SC

L E =2A~from(la)or(lb)

A S , from (4a)or(4b)L E

L E =2A:from(la)ar(lb)

AS, from(6b)LE

L E = LE rom(l5) x R2from(S)I from(8)

Notes: l.here lsindicated,subtract 0.7854df from &fora hollow part:

2. Numbers in parenthesis are ormula numbers from T a b l e l l and from this table.

Notation dlmin =minimumminor diameter, external thread,f lot form (was &min), inch.

dh=hole diametehexternally threaded part,inch. If thwe is no hole, dh=O

F =axial load on externally threaded part, lb

S, =shear stress, psl

S,/.cwnbined shear stress,psl

T =transmitted wrench torque n threaded &ection(approximately half of the

I n f o r m ~ l a ( l 2 ) , d ~ m i n = d ~ b s c - ~ H = d ~ , ~ -7 ,.2990

applied wrench torque), in.-lb.

REFERENCEPARAGRAPH

70.6

70.6

70.7.3

70.7.4

70.7.5

’ 70.7.5

38””””ided by IHS Sold to:HOLTEC INTERNATIONAL, W0847024Not for Resale,2010/2/2 15:49:11 GMTeproduction or networking permitted without license from IHS



F E D - S T D - H 2 8 / 2A H m 7777777 O O O L 5 7 L 7 m

FED-STD-H28/2A

L

SECTION FOR MINIMUM

SHEAR AREA OF

I bSECTION FOR MINIMUM

SHEARAREAOF

EXTERNAL THREAD

MAXIMUM MINOR DIAMETER

OF INTERNAL THREAD

MINIMUM MAJOR DIAMETER-OFEXTERNALTHREAD

FIGURE 2. B. I SHEAR AREAS AT MINIMUM MATERIAL

70.3 %earareas a.t basicsi ze . The geometricshear mea of an externalthread at basic size is e q u a l t o the area. of a basic size threa d which is

intersected by a cylinder with a diameter equsl t o the bas ic minor diameter.

Formulas (6a) and (6b) of table II.R.l are used f o r calcu lati on. The eo me tr icshear area of an internal thread at basic size is not ordin arily used forc d ulat ions.

70.4 &eararea implified formulas. Formulas ( 7 ) and ( 5 ) in ab le II.R.laresimplifiedformulas fo r inte rna l and external hreadshear areas. They a r ebased upon empirical da t a and give shear areas which vary from the geometricm i n i m ma te rialshearareas. In som ca se s, es t daka agrees more clo se lywith these simplified formuls. shear areas than with geometric shear areas.

f-.



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F E D - S T D - H 2 8 / 2 A TH W 7 9 7 9 7 7 7 I JOOhG-2 7 M

70.5 Shear area, combined fa i lu re of external and int ern al hre ads . \Thenthe mtinp ex te rna l a n d interns1 threads are on parts m.nufac.t;ured frommaterials of approximately equal strength, fai lure w i l l usually tdce place inboth hreadssimul- taneous ly. Thresri bendingduring Pa il m e changes the hreadgeomt ry in th i s case so that effective shear area is signiPi .cmtly smallerthan those calmlated from form~lms discussed in 70.2, 70.4 and 70.4 above.ForLmla (7 ) in . t abl e I I . R . l is an empirica.1- formula which gives an apFroximakeequivalent or hiscase. !Tumerically, i t descrihes a Fa i lme at; thepitchd i m t e r of one of the hrea.ds.

70.5 *ensile stress. Formula. (1 1 i n t abl e I I R. 2 is often used fo r accent-ance of external ly threaded %st,eners with ultim ate tens ile stre ngth , piel.dstrength, o r some otherselected stress level appl ied to Pt inorder t odetermine therequired axid. %est oad. ?hen threadsare u s e d in a ;ioin.t, a.

tightening torque is applied. t o overcome -Friction und-er a hol..%head or nu+, t o

overcome th read ric- ti on , and t o &vel-op th e axial- 1-osd. Phis oraue esul tsi n x shear stress, which \&en combined with the +en sil e str ess from. the ax-i~l.

1-osd, cawes m-~increase i n the ef f ecti ve t ens i l e stress. Formula (17) Intabl-e TT.R.2 describes t h i s situakio n. .Fkperience has shmm thah f o r a. so l ide.xternally hreadedpart; , he combined stress i-s general-lv shout; ?M ea . te rt h ~ n?ze t ens i le skress ca1culs.ted from formula. (1 1). Therefore, i n thi s cme,the combiced stress i a often asswrled t o he 1.28 or is notconsid.ered due t osatisfactory experience with the Factor of Saf-ek used..

7O.?.l I f f a i lu re of a fastening system usingstandard. thremled fwtene r sshoul-c!occur it is gener,dlv more economical. t h m t th e externall;gr hreaded par t

will break rs.ther han hat either t he ex-beynal- or j.nternd- thread will striD.In other words , the lenet;)? o f thread engagement shou1.d Fe suf f ic ient t o developt he P u l l strengbh of the screw ?hus, the ength of internal. hread and. thedimensions of th i s thread , pa~t icul -ar ly its minor diameter, should lx suchth at , t$-inp, in to account a. possibbe difference i n . stren@h of material of theinternal. and ex+rnal!. threads, the t;hread.ed porkion of the externally threadedpart wil-l breakbeforeeither the efiernal. or internal. thre8.d.s str ip. The t otkis situa.?ion, engths o f engqqement f o r m ~ L a s re rleriverl from shew form1.a.swith ten si l e s t r ess area A, replaced. hy 2A.S because the required . area i nshear is twice the tensi le stress area i n ord.er t o c?.evelop th e f111.1. s t r e n d h ofthe externally thresded past. "his relat-i.onshin i s based upon experiments mdeby the Vadional Eureau c f Stsnd.ards i n 1929, in which i t was found. th?,% o ~hot-rol.led m d col.d~-rol?.ed. t e e l , mcl hrws scram and nuts, thi s factorvaried

from 1.7 t o 2.0. %e ef fec t of combined stress is not 2ken i c t o account i ncalculat ion o f ZIF: beca.we %headder! shear l oad sffects bo?h tensi7.e anil shearst re ss es in approximately he sme proportion.

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F E D - S T D - H 2 8 / 2 AH 9 9 ' 7 9 9 7 7 0 0 0 3 5 7 3 O W

70.7.2 A l formulas fo r le ng th of enegement,given i n tab le I I .R.2 yieldapproximate values since they are based i n pa rt upon shear areas which are not;exact due t o m t di la ti on which varie s with geometqv, fr ic ti on fo rc es , andmaterialproperties. Also, theeffectiveness of par t ia l h reads , n hecountersinks (or chamfers) on the ends of the internal thread, is notalwaysthe same. For calcu lati ons, appro ximt ely half he count ersin k dept h may beconsidered in he en gt h of engagement. I t is advisable hatcaLculations oflen gth of e n e s m e n t and correspond.ing load. cap a,b il iti es of a threaded joint bechecked by actual tests, f o r c r i t i c a l j o i n t s .

70.7.3 fien the externally a n d internally hreaded parts are made frommaterials of approximately the same strength, required ength of enegement i nformula (13) of table II B.2 mw be appl ied. This assumes a, combinationfa il ur e of both hreads. See 70.5.

79.7.4 When the s t rength of the int ern al thr ead ma,terial.lyexceeds t h a t ofthe external hread, required ength ofengagement i n formula, ( 1 4 ) of takleI I .R.2 may be zpplied.This assumes shear of the ext ern al hre ad and us es th egeometricshear area of the minimum external thread. See70.2. A s l i @ t l ylonger or shorter len&h of eneR ment will 'be indi cated i f the s implif iedformula ( 5 ) i n t a b l e I I . B . l is used.

70.7.5 When the s t rength of the extern al thread mter i a l ly exceeds th at ofthe nternal hread, required ength ofengagement i n formula(16) of ta bl eI I . B . 2 is u s e d . This i s based upon the ntern al hread strip ping oad beingqual t o t h e nominal e xtern al threa d strip ping load which w i l l develop f u l ls-brength of th e ex te rn al ly thre,aded par t. If R /R2 is l ess than 1 , see

70.7.4 and i f approximtely equal to 1 , see 10.4.3.

70.7.6For an adjusting or lead screw, or i f th e connection w i l l befre que ntl y unscrewed, the cal cul ate d LE should be ncreased t o a l l o w fo r t h eexpected wear on the flanks of the threads during the useful l i f e of thecomponents.

70.7.7 Por ta.pped h ol es in sh ee t metal, the maximum s i z e of th e screw t o bespecified should be such that the thickness of sh eet equal s the LX required todevelop f u l l strength. norder ouse the largest possible screw, i t is

be t he prac t i ca l minimum. I f i t should prove t o be mpracticable t o reduce theminor diameter toler ance to such a value, it m a y benecessa.ry t o decrease the

minimum minor diameter of the inter nal threa d and to inc rea se the minordiame ter ole rance by th e same amount. If t h i s is done, the m x i m minordiameter of the screw must be reduced by t h e same mount t o preventin te rf er ence and th e minor diameter of th e GO thread ring e g e must likewise bedecreased, a s t h i s is the onlycontrol of the minor diameter of the screw. I nall such cases, where dimensions are a l te red f rom those calculated according t othe standard, he hreads should be designated as speci f ied in secti on 6.7 of

necessary tha t theolerance, TD1, on th e minor diameter of theolehould

ANSI B1 1-1 982.



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F E D - S T D - H 2 8 / 2 A H m 7777777 0 0 0 3 5 7 4 2 W

70.7.8 For retai ning coll ars on sh af ts where the expected axial forceresisted by t h e c o l l a r is appreciably less than the t emi le fon=e t h a t t h es h a f t i t se l f is capableof resisting, LE need only be long enough to -w i tb t an dthe expected axial fon=e on the collar . If Fc is the axial f o R e t o becarried by the collar , UTS is the t emi l e s trength of the shaf t and WSnis the temi le s t ren gth opthe co l la r , ca lcu la te the required engthofergagewnt fmm one of the following formulas:

a. Collarhreadtrip: L E = -2FcUTSn X-Sn from2a) , (2b)or (3)

L E .

b.hafthreadtr ip: L E = 2FC

UTSs x-Ssf rom(4a) , (4b)or (5)L E

c . Combination hreadstrippingwhen UTSs = UTSnapproximately:

2FCL E =

(UTSSor UTSn)X-S from7)

L E

Not e: Numbers in parenthesis are form ula nu mbers fro m tablen. .1.

70.7.9 For hollow, t h i n w a l l threaded parts as the w a l l thickness of eithero r bo th the in te rna l and ex te rn al mnïbem becow s thin , the tendencyof the

external wmber t o enlarge and the in te rna l =&er t o neck dawn i n the threadm m h a t an LE greater than given by formula must be wed, a lso that thetolerances on minor d i a mt e r of the i nt erna l t h n d & major diamter .of theexternal thread, TD, and Td, m u s t be small t o obtain the m a x i m u m practicabledepth of t h r e d engagemnt.Tor components having threads on th in -wal l tubing,tests under actual woIking cond itio m shou ld be d e o determine properse lec t ion of wall thic kness es, leng th of engagemnt, and pitch of hread.

80. Thread pmpo rt io m in re l a t io n to tapping.

80.1 In heprod ucti on of threads it is comidered mpractical t o t a p athread unless its nominal d i e t e r is glpater t h a n s i x t ims th e basic threadheight; theRfore, when the ra t io of D t o h is less than 6 , the use of a largerdiamter , a f iner p i tc h of t h E a d , o r both, should be comidered.

80.2 The s i z e of D is a fa ct or n co nt ml li ng ap breakage. Tap breakageis infrequent if the A i e t e r of the tap is over O. 5 i n o r i f the length oft h p d t obe apped is less than O. 9 . For s izes lesa than O. 5 i n ad lengthof threadover O. 9, a p breakage ca n- be minimized b;y use of a large D t ha tis TD1 maximum. b e v e r , t h i s m m h a t LE m y have t o be inr: eased 1develop the fü l l s trength of the SC m .



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F E D - S T D - H 2 8 / 2 AH m 7777777 0001575 m

with = 0.7854 (dbsc - 0.9743) 2. In his case, A, maybe read asn

1.492from table 130f ANSI 81.1-1982.

dh = 0.792

n = 8

DImax = 1.390.from table 3Aof ANSI 81.1-1982

d2min = 1.4093 from table 3Aof ANSI B.1.1-1982

90. Examples of threaddesign.

90.1 Gun barrel hread. A ,gun barrel is subjected o an internalexplosivepres sure hat produces a tensile stress in he hreaded end. The length ofengagement of the thread s should be s u ff i c ien t to produce a m i n i m area i nshear on t he thr ead s of the screw i n l i n e with the minor diameter of thetapped hole threads equal to twice the st res s are a of the threaded portion ofthe barrel . Assume tha t the thread on th e ba rre l i s 1.50-8UN-2A and theminimum internal diameter of the ba r r e l at; the threaded end is 0.792 inch.

Note: Symbol notation and formula numbers inparenthesis are i naccordance with ables I I . B . 1 a n d II.B.2.

a. Required length of engagement is found using formula (14) for a hollow Part.

L E = 1.*(As -0.7854d f )

b. Calcu lating from th e above yiel ds a required engthof engagement of0.777 inch. By reducing he nternal thread minor diametert o l e r a p e by ha l f , the r e su l t inp Dl max is reduced t o 1.3775inches, and th e requ ired ength of engagement is reduced t o 0.714inch.



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F E D - S T D - H Z B / Z A T H m 7777977 0003576 6 W.~

90.2 Screws mounting brack et t o cast i ronpa rt . The dimension is requiredfor the liwgest s teel cap screw that can be u s e d t o hold a. bracket on a c m t.i ron b@y. The tens i les t rength of t h e s t e e l is 60,ooOpsi, t h e - t e n s i l e

strengbh of the cast iro n 20,000 p s i , and the thickness of the cas t i ron i ssuch th at he en g th of thread enmgement cannot exceed 1.750 in. The screwson t h e toy, side of the bracket will be in tensio n.

>Tote: Symbol notation and Pormula numbers inparenthesis are i naccordance with ables 11.3.1 and II.B.2.

a.

b.

C.

d .

e.

P.

Since the external thread mterial is considerably stronger hantha t of the in ternal thread material, i n accordance with 70.7.5,formula ( I C ; ) w i l l be u s e d t o crr?lculate the length of enpagementrequired.This ormula is applied for IJ? based upon shear of thein te rna l thread. To confirm t h i s assumption, R 1 /R 2 should becalculated.

R1 canno t be czlculated from f ormul a (8) u n t i l a, thread size isselected. Py definition, however, R, is t h eratio of externa1threadshear area t o internal- hreadshear area,. An approximtion

Of R, , can be madeby us in g th e siwlified formulas for she arareas s o

R2 is calculated from f o r m u l a (P).

From b and c above, R1 /R = 2.5 approximtel,y. Thisvaluebeing greater han 1 c o n h m t h e use of Pormul~a(16) Porcalculation of length of engagement.

R om formula(16) i t is seen that the length of ensgement must beapproximately 2.5 imes as long a s that required i f shear i n theexternal hread were thecontrol l ingfactor . Thus, since he m x i -mum available LE is 1.750 inch es, the approximate LE required forthe screw t o develop füll strengbh is.1 750/2.5 =0.700 inch.

Inasmuch as the hole is tapped in cas t iro n, a relat ively coarsethread would berequired, hat a ITNC o r coarse r. The most resld ilyavailable screws would be UNC. Select hread sizes from f igme2.3.2 which yield L 3 of ap roximateLv 0.700 inch. Pimre 2.R.2 wasdeveloped from formula (15P.

For 1" - 8UNC, LE/D =0.594 and LE =0.594

For 1 % -7UNC,LE/D =0,592(est.)and LE=0,656

For I L -7UNClLE/D=0.600(es t . )and LE=0.7504

44

ded by IHS Sold to:HOLTEC INTERNATIONAL, W0847024


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F E D - S T D - H Z A / Z A H W 9 9 9 9 9 7 7 0001577 B m

FED-STD- H28/2A

9. For a bracket screw, the preferred thread class is 2Aso the selected thread is 1- 7UNC-2A81

for the cap screw. The corresponding hole in he body wouldhave a 1~ -7UNC-28 thread.

h. The thread should be checked in accordance with formula (16). Formula(l6j may be expressedas follows:

2 As RIL E = x -

3.1416Dlmin x 7 R 2

with As = 0.7854 fibsc n 2I In this case, As may be read as

. 0.763 from table 8 of ANSI 81.1- 1982.Dlmjn = 0.970 from table 3A of ANSI B l.1- 198 2.

æ

Formula (6b)37 Dlmin

" I - Formula2a)-

n = 7

dmin = 1.1064 from table3Aof ANSI 81.1-1982

D2max = 1.0416 from table 3A of ANSI 81.1-1982

SO RI = 0.863 .

R 2= 0.333 from cabove.

i, Calculating from the above yields a required length of engagement of 1.729 nches, This isacceptable since it is.less than the maximum available engagement length of 1.750.



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