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Specification for interna! micrometers (including stick micrometers)

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BS 959:2008

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Toxt :iffecttd "l A1nd.No. Amendments lssued slnce publication

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Summary of pages Thisdorument comprises a front cover. an inside Ircnt rever, pages i ton. p

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Contractual and legal considerations This publication dces not purport to indude aU rhe ncc~ry prcvlslcra of b conlraCl. Us.c:rs a1c rcsponslblc for lts COtTCCL appllcblion. Cornpliance with a Bridsh Standord cannot c.onfer lmmunhy Ircm legal obllgations.

Presentational conventons 'rhe prcvlstons of thts stenderd are presented 1n roman (l.e. uprlght) typc. lts requlremcnts are expressed ln semences in v1hlc:h the prlndpal allxffiary vcrb is "'shall". Con)nlentary, exp!anation and general infom~ative rnaterial is pfeu:.nted irt snraffet itafi< type, and does rtot conjtitute a rir>tntative element:

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lnformation about this document This British Standard has been fulJy revised to bring it up to date.

Supersession This 8tisli Standard seoerseces BS 959:l950, v1hich is withdrav-1r1.

Publishing information This British Standard is published by BSI end came into efteci en 30 November 2008. lt was prepared by Technlcal Committee TDW/4. Technc.af producr teallzaclon. A li.st of organizarions: represented en thls

@8Sl 2008 1

Thfs standard eiso cevers stick mlcrcrnete-s, \Vhich are dr.s1goed for the measurement of longer interna! lengths. and compri$e the follo~ving parts: a) a 1SO mm or 300mm or 6 In cr 12 In mltrorneter unlt. Iltted

with "b rnkrometer of 25 mm ce 1 In rangc, and h

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Ihe followin9 reterenced document is indfspe11sable ter the epptlcatlco of thls dccument. lbe latest edlticn of the referenced document (induding any amendments) eppties, BS 84, Par al/el SCfE'\V threads of Whfhvorth (otm - Requireme.nts

2 Normative references

85 959:2008 BRITISH STANDARD u: en

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6.3 Thc dstance from the barrcl to the raading end of ihe g~duat!on on the thimbte (Figure t. dimenslon 8} shall not exc.eed 0.381 mm or 0.015 in,

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6. 1 The dlemeter of tbe.qredueted edge of tbe thimble (Figure 1, djn,cnsion A}shblt be no lcss lha11 10.32 mm or1V,, in.

6.2 The angle of the bevel (Figure 1, angle u} shall be no more Ihan 20. NOTE lt Is recommended tllat, for e ase of readlng, the angle af th~ bevel 11101.1/d be IS-.

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6 Thimble and barre!

5.6 A meens shalf be prcvlded {e:.g. 1' spanner or keyl for ccmpensetlnq ter wear between tbe screw and run.

5.2 The screw shall be lubricated with a thin, light, ncn-corrosive oil, and shall run smoothly throughout the length of its trevel.

5.3 h sha11 be pcsslble, ehher by means of the adjusting nut or by cther meaos, to arrenqe Icr the thlmble to be suffidently tlght for tbe m crome ter to reta in lts readln_g efter being set.

5.4 "rbere shall be no perceptible becktasb between the spindle screw and nut,

S.S When thc mlc-cmetcr s al lts maxiroum rcadlny thcr screw beyond e11

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6.S The thimble and barrcl sh.till be yr.)duatcd as follows. a) Fol' me trie rcadlny mkrcrncten, the thlrnbte shall be 9r21duatcd

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9 Adjustment Each micrceneter shalt be provided with a means for adjusting the zerc setting (e.g. a spanner or key), svch that, after resetting, the paru are seeured and ihe original eccuracy of abe instrument 1s not irnpaiired. In rnictometcr sets in which ~adi cxtcn.slon rod has its own mc..,suting tace, a suitable adjustment for zero setting sh(llll be incorporated fn each. e>ctension rod; for example, Lhe anachmen1 of the anvH by mea ns of a friction4ight fine p?tch thread. NOTE In such types rhere should be no adjurrment on the micromerer head In mlcrometer sets In \vhich the extensfon rods rake the form of cJJst.t1lCc J)ieeAsun:n1enr, ;:ar.h rdll sfiould h~ rnarkt>:el wfth rhe range otmessuremern fot which it is applicabfe. NOTE 2 In each folnt of cr.e .1Sse1nbly, one of Lhe abuttlr>g lacesshoud be provldecl wlrh dftt cle~riJl')(e groo ves.

7 Extension rods

BS 959:2008

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BRITISH STANDARD en en (.)

u: en o 85 959:2008 BRITISH STANDARD >- 10 a Accuracy o Atan amblerrt temperatuee ot 20 t(~ each measurinq head wh:h its

't:l esscctated extenslcn r()d:s. (and collars if used) shall conform to the Ql limits of error specified In Table 3, when the thlrnblc reading ls zero. o ~ Table 3 Maximum permissible errors ~ o Mtasurlng rangt Maxlmum permisslble e"' u e in length ::) mm mm (') 25

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15 Packing Each measuring head shllll be o C\I

The tc.fmlnal faces shall be hardcn~d to a dlamond pyfamld hardocss numbr of not less than 800 (62 on thc RO(kv1cll e scalc}. Thc abutmcnt faces shall be hardened to a diamond pyramid bardness number ot not less then 700 {59 on tbe RQCkwell e s.c:a1e}. The abutmern faces shall have a minimum radial width of 1.27 mm oro.oso in. The abvtment faces sba be leppcd Oat and parallel to each other and shal! be normal to the axis of the rod (defined as the Une Joning the centres of thc fi11ishcd cnds) to within O.OOS mrn or 0.000 2 in ecross lheii' diameter~.

The redlus of curvawre of the terminal faces of the micrometer unit s.hall be sJighUy tess than half cf the smanest measuring range .of the mlcrometer unlt.

5 Mi(wrm:lei< unil Abu1mP.n1 tace 7 Elfle~ion tod 8 Endpiece

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1 T!!orn'linAI '"' 2 Fied insula1in9 steeve ) Screw~ joint ~in ,. 16 t.p.i Wliit 4 LOOie in-su l~ting ueeve

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17 Screwed joints The saewed [onts snan bave threads of % in nominal diameter ind whh 26 t.p.l., In ecccrdence with es 84. There shall be sufficient play between he externa! and interna! thread.$ ot the joints to perrnit the abutment faces of tbe vadcus parts of the mlcrcmeter to butt tgcthcr sotidly. NOTE 1 The fema/e thread sltould be biJsic size, the nec~SScJI)' fre-edon1 ~i119 kCured by lJ r..:

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21 Rigidity 21.1 When tested In acccrdance wlth 21.2, the deectlon of the mld-pclnt

undcr the "pplltd load' shall not cxcccd 3.81 mrn or 0.1 Sin. 21.2 ASS or I in f~ogth having % in x 26 t.p.i. Whitworth forr11 threads on ene end and 9.5 mm 'o!. 0.5 JrJJTI pitch me trie rhrMds on lhc otber end lor compatibility f)Ufp-05t!S

SS 959:20-08 u BRITISH STANDARD (/) fI)

25 Packing Each mc.21suring unft sltall be coetcd ~vlth a suitablc thin, ocn-ccrrostve light oil and shall be ::oecurety wrapped. Each extension rod (and gap setting gauge, if applkable) shall be coeted with an antl-.corrosive preperetlcn (e.q. h.arddrying tancn),

A sultablt case shall be provded wlth cach mtccrnerer sci, 24 Case

FigurC'. 4 Gap setdng gauge

23 Gap setting gauges (see Figure 4) When sopptied, gap sening gauges sha!I bave a gap of elther 165 mrn :t 0.003 mmf 67S In e 0.000 1 rn or 318 mm e 0.005 mm/ 12Y.i in ,t. 0.000 2 in. 411cco1ding to the length of the rnlcrometer unlt. The taces of the gap shall be hardened and Rat to v1ithfn 0.003 mm or 0.000 1 in.

22 Marking The rnkroroeter unlt shall be marked "150-175 mm (6-7 in) with end piece" or "300-325 mm (12-13 ln)with end piece", and tbe micrcmeter head and each extensin rod ot a set legibty and permanentJy ma.rked with a commo-n ldentlficatton nurnber. "rhe mkromctcr unlt shall be s-lmllarly markcxl with thc manufacturer"s uarne cr trade merk.

NOTE When lengths f brirwr~n 1.2 m and 3.6 n1 cr 4 ff'et and 12 feet are assembled for use. te unit shoufd be wpported et reasr et the ends and in rhe centre. For Jengths over 3.6 "' or 12 le!t. the unlt sJioufd be sup;>oned "' reyulltr lnteNbls frld rhc rt1{jJr1/1lt1l't1 sep11r.,tlo11 bclWCf'n rhe supporu shl)ulrJ nol tKceed I .8 111 or 6 fe~t. F411wc to JUPl)rt ('l)uld te5Ult in dantage to tlie lnstmmenr.

BRITISH STANDARD (f.1 fl)

85 959:2008

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A.3 Procedure A.3. 1 Garnp thc m('asurng he.ad In thc.- vce block w'hh lts axis lo sine wlth

the sensitive indicator aind the flat contect tace juruposed to the rounded contaa face of the measuring heed.

A.3.2 Set thc measuring head toread exactly sero. A.3.3 nsert the gauge block between the two ccntact faces. A.3.4 Set the lndiQtor toread aerc. A.3.5 Test the measuring he.;id ata numberof readin.gs a1ong its traverse

and al the serles of readlngs sbcwn In Table A. 1. To test the accuracy of tbe reading of the head al any point, set rhe measuring head to thc rcadng givc.-n ln Table- A. 1; the- irlitlal s~zc of thc gaug~ block will be reduced 1n length by rhe val,1e of me reading. Any error in tbe reading will be reveated by a corresponding departure of the fndicator pointer-from its aerc posftion.

A.2 Apparatus A.2. 1 Vce-block. A.2.2 Scnslrivlty lndl

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Bibliography SS 817. Specificottion tor svrla{e pl.,tes 85 869, Spec;ncarion for toolmakcrs (fau 4nd high pre,;sior, surl~ce pfares SS 870, Specification for externa/ mioometers 85 887, Spec1Hcarian for prec1$ion vernier calliperi BS 906, Sp~dfcat1on lor eng1neers' parallels SS 907, Spectficalfon for d;af gauges for llne for ct1ginccrs' conpbratrs for C'Xtcrf)af n1 for precision vernier height gauges 85 1685, Specificatiott for ~vel protractors (n1rchani,al ilt'ld optiCJtl) 85 1734, SpecifiQjtion tor n11Cfometer heads SS 1790, Spec;fi o o ('I ~ o - (') ~ ~ (!> > e ':J "' ro CD s: ~ ::) o C/) ?:- (/) ~ (!> > e,

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