Pipethread管螺紋Twocommonpipethreadsizesexist,thetaperedNationalPipeThread(NPT)andthestraightNationalStandardFree-FittingStraightMechanicalPipeThread(NPSM).Thetaperedthreadsareforjoiningandsealing,thestraightthreadsareonlyforjoining.TheDry-sealthread(NPTF)allowsforjoiningwithoutsealants.Threelesscommonthreadsexist,theGardenHoseThread(GHT),FireHoseCoupling(NST)andBritishStandardTaperPipeThread(BSPT).TheNPTandNPTFthreadsareinterchangeablewithsealantssuchasPTFEtape.Noneoftheotherthreadstandardsareinterchangeable.FemaleNPTthreadscanbedesignatedas"FPT"andmaleNPTthreadscanbedesignatedas"MPT."Pipesizesdonotrefertoanyphysicaldimensions.Theoutsidediameterofeachpipeorfittingmustbemeasuredandcomparedtothetableforsizeidentification.Forexample,a3/4"NPTpipethreadhasanoutsidediameterof1.050inches.Eachthreadsizehasadefinednumberofthreadsperinch(TPI).The3/4"NPTpipethreadhas14threadsperinch.BoththeTPIandODofthethreadarerequiredforpositiveidentificationofthreadsizebecauseseveralsizeshavethesameTPI.NominalPipeSize(NPT)ThreadsPerInchApproximateCaliperMeasurement1/8"270.38"1/4"180.55"3/8"180.63"1/2"140.80"3/4"141.00"1"11.51.25"1-1/4"11.51.55"1-1/2"11.51.80"2"11.52.30"DefinitionofpipethreadacronymsNPTNationalPipeThreadFPTFemalePipeThreadMPTMalePipeThreadPTFSAEshorttapepipethreadNPTFAmericanNationaltaperpipethreadfordrysealpressure-tightjointsNPSMAmericanNationalstraightpipethreadformechanicaljointsNPSIAmericanNationalstraightintermediatepipethread管螺紋的規範及用途PT(英制管用推拔螺紋)以癰是使用面直角的螺紋峰,現在將規格統一爲軸直角者.JIS定爲耐密用而組全外螺紋和內螺紋.PT外螺紋除了配合PT內螺紋,有時也配合PS.PS(英制管用推拔螺紋用平行內螺紋)屬於JIS內PT的規格,舊JIS裹有外螺紋,現在已被取消,對方的外螺紋規定要有用PT.(耐密用)PF(英制管用平行螺紋)JIS所定的機械接合螺紋,外螺紋與內螺紋成一對,許容差之設定與PS不同,採用一般固定螺釘方法,外螺紋在負邊,內螺紋在正邊,成爲無餘隙公差.精度有A級.B級二等級.NPT(美制管用耐密推拔螺紋)制定在ANSI規格中,稱爲美國標準管用推拔螺紋,有外螺紋與內螺紋.NPT外螺紋不但對NPT內螺紋配合,有時也配合NPSC,這點類似T.紋峰與根切成同形,又因公差,大餘隙.壓緊兩種配合都可用.如用潤滑齊,則變成耐密用,耐密用者另有稱爲幹封閉之如NPTF,NPSF等付有F之一群.NPTF(美制管用耐密推拔螺紋)NPTF外螺紋,像PT.NPT有時也配合NPSF.NPSI(都是內螺紋).因這種螺紋都是峰尖.根淺.峰不是密接於根就是食進.可防止在此部份變成螺旋狀間隙,這是前述耐密性之理由.PTF(美制管用耐密推拔螺紋)耐密推拔螺紋.外螺紋之對方是NPSI,內螺紋之對方是NPTF.齒形和各部尺寸與NPTF相同,但內螺紋之小端徑及外螺紋之大端徑短一節距表.也是幹封閉用.NPTR(美制欄杆管接頭)ANSI芝欄杆接頭用管用推拔螺紋,有外螺紋與內螺紋,不和別種配合.下記螺紋長度以外和NPT相同.如2寸以下外螺紋之管端短三節距,2寸以上都短三節距,內螺紋也在管口削峰擴大2.5~3節距,剩餘螺紋長度比NPT作手轉配合短1~2節距.ANPT(美制管用耐密推拔螺紋)MIL(陸軍規格)之管用耐密推拔螺紋,由外螺紋與內累紋成組.螺紋基本上與NPT相同,量規制度如NPTF使用L2規,L3柱塞規,相異點爲使用六段切除之外徑用,風徑用推拔量規,量規之峰部切斷大小另有規定.NPSC(美制直管接頭用管用平行螺紋)如PS只有內螺紋,對方要用NPT.有效徑許容差與PS相同.正負同尺寸,精度也大致類似.NPSC(燃料管用耐密平行螺紋)主要用天軟材料,外螺紋採用NPTF(幹封閉).有效徑許容差設于負邊,公差定於NPC之1/2(等於單邊公差),螺紋齒形與NPTF相同,作成峰與根間無餘隙,將推拔外螺紋緊配,擴大內螺紋管口適合使用.NPSI(中間管用耐密平行螺紋)有效徑許容差在正負兩邊,負邊.大公差和NPSF相同,可以說是近於基準有效徑之中間的尺寸.對使用硬或脆性材料時...
