英美螺纹标准对照表
美制迫牙丝攻钻孔径／英制螺纹／针车用螺纹
SM1\4-28 5.721-5.368
SM9\32-28 6.508-6.648
SM11\31-28 8.092-8.432
SM3\8-28 8.880-8.015
美制管螺纹
SM7\16-28
10.46610.401
SM7\16-16 10.037-9.967
钻孔径
SM1\2-20
11.81911.749
美制迫牙丝攻钻孔径
规格
精度等级 G4－G6 G7－G8
NO.2-56UNC 1.94
NO.3-48
2.23
NO.4-40
2.5
NO.6-32
2.83
NO.8-32
3.07
3.75
NO.10-24 3.78
4.3
NO.12-24 4.24 4.56
1\4-20
4.9
5.72
5\16-18
7.24
3\8-16
公制螺纹孔径
（R－S）（R－G）
等级
规格 m1
m1.1
m1.2
m1.4
m1.6
m1.7
m1.8
m20
m2.2 m2.3 m2.5 m2.6 m3 m3 m3.5 m4 m4 m5 m5 m6 m6 m6 m7
牙距 0.25
G3－G4 G5－G6 0.86 0.88
0.25 0.96 0.98
0.25 1.06 1.08
5\16-18unc
6.6
6.731 6.401 1\4-28unf
3\8-16UNC
8
8.153 7.798 5\16-24unf
7\16-14UNC 9.4
9.55 9.144 3\8-24unf
螺纹规格-美制、英制、公制对照表
各国标准螺纹基本尺寸对照表
英制管螺纹基本尺寸及公差（牙形角55º）BSPP英制锥管螺纹基本尺寸及公差（牙形角55º）BSPT美制管螺纹基本尺寸及公差（牙形角60º）UN(F)公制螺纹基本尺寸及公差(牙形角60º) M55°圆锥管螺纹基本尺寸对照表最新下载-汇兴达55°圆锥管螺纹基本尺寸对照表最新下载-汇兴达55°圆锥管螺纹(BSPT)2 R5 5"138.432.30911136.951135.4721.479R66"163.832.30911162.351160.8721.479聊城市鑫茂祥管业有限公司专业经营钢管规格：5mm*1mm—1020mm*200mm合金钢管、外径22mm-127mm冷轧无缝钢管、外径127mm-600mm.壁厚16mm-100mm.外径精度±0.5%,壁厚精度±5%热轧中厚壁无缝钢管、16Mn外径400—1600mm、壁厚20—60mm 的大口径厚壁卷管.可定尺到16米及各种规格的无缝方管、异型无缝钢管等.常备钢管种类有:构造用无缝钢管、流体用无缝钢管、液压无缝钢管、电力用无缝钢管、石油输送用无缝钢管、化肥设备用无缝钢管、煤矿用无缝钢管、不锈钢无缝钢管、化工用无缝钢管、纺织机械用无缝钢管、汽车；水利用无缝钢管.精密无缝钢管、光亮无缝钢管、军工医疗用无缝钢管、管道用无缝钢管、支柱用无缝钢管、合金无缝管、高压无缝管、大口径直缝焊管等。
适用于工程、煤矿、纺织、电力、锅炉、机械、军工等各个领域。
公司以良好的信用、优质的产品、雄厚的实力、低廉的价钱享誉全国30多个省、市、自治区、直辖市及国外.产品深得用户依赖。
管螺纹的基本尺寸表(2010-10-25 15:57:35)转载▼标签：杂谈表（1）螺纹基本尺寸G1/2 、ZG1/2 (单位:mm)尺寸代号每25.4mm类的牙数n螺距p 牙型高度h圆弧半径r≈基面上的基本直径基准距离有效螺纹长度大径（基准直径）d=D中径d2=D2小径d1=D11/16 28 0.907 0.581 0.125 7.723 7.142 6.561 4.0 6.5 1/8 28 0.907 0.581 0.125 9.728 9.147 8.566 4.0 6.5 1/4 19 1.337 0.586 0.184 13.157 12.301 11.445 6.0 9.7 3/8 19 1.337 0.586 0.184 16.662 15.806 14.950 6.4 10.1 1/2 14 1.814 1.162 0.249 20.955 19.793 18.631 8.2 13.2锥管螺纹的基本尺寸表（3-28）1/2PT 、1/2NPT表（2）螺纹基本尺寸 (单位:mm)螺纹标准的一种.按外形分圆柱、圆锥两种；按牙型角分55°、60°两种。
各国标准螺纹基本尺寸对照表
英制管螺纹基本尺寸及公差（牙形角55º）BSPP英制锥管螺纹基本尺寸及公差（牙形角55º）BSPT美制管螺纹基本尺寸及公差（牙形角60º）UN(F)布锥管螺纹基本尺寸及公差(牙形角60º) NPT公制螺纹基本尺寸及公差(牙形角60º) M55°圆锥管螺纹基本尺寸对照表最新下载-汇兴达55°圆锥管螺纹基本尺寸对照表最新下载-汇兴达55°圆锥管螺纹(BSPT)聊城市鑫茂祥管业有限公司专业经营钢管规格：5mm*1mm—1020mm*200mm合金钢管、外径22mm-127mm冷轧无缝钢管、外径127mm-600mm，壁厚16mm-100mm，外径精度±0.5%,壁厚精度±5%热轧中厚壁无缝钢管、16Mn外径400—1600mm、壁厚20—60mm的大口径厚壁卷管，可定尺到16米及各种规格的无缝方管、异型无缝钢管等.常备钢管种类有:构造用无缝钢管、流体用无缝钢管、液压无缝钢管、电力用无缝钢管、石油输送用无缝钢管、化肥设备用无缝钢管、煤矿用无缝钢管、不锈钢无缝钢管、化工用无缝钢管、纺织机械用无缝钢管、汽车；水利用无缝钢管，精密无缝钢管、光亮无缝钢管、军工医疗用无缝钢管、管道用无缝钢管、支柱用无缝钢管、合金无缝管、高压无缝管、大口径直缝焊管等。
适用于工程、煤矿、纺织、电力、锅炉、机械、军工等各个领域。
公司以良好的信用、优质的产品、雄厚的实力、低廉的价钱享誉全国30多个省、市、自治区、直辖市及国外，产品深得用户依赖。
管螺纹的基本尺寸表(2010-10-25 15:57:35)转载▼标签：杂谈表（1）螺纹基本尺寸G1/2、ZG1/2(单位:mm)锥管螺纹的基本尺寸表（3-28）1/2PT、1/2NPT 表（2）螺纹基本尺寸(单位:mm)螺纹标准的一种，按外形分圆柱、圆锥两种；按牙型角分55°、60°两种。
公制美制英制螺纹对照表
公制/美制/英制螺纹对照表A型美制螺纹（UNF）常用规格外螺纹螺纹-4 9/16"-19牙 14.28 13.08 -6 11/16''-16 17.46 16.1-8 13/16''-16 20.64 19.28-10 1''-14 25.40 23.57-12 1(3/16)''-12 30.00 28.32 -16 1(7/16)''-12 36.51 34.67 -20 1(11/16)''-12 42.86 41.02C型JIC37度美制UNF螺纹常用规格-4 7/16”-20 11.11 10.03-5 1/2”-20 12.70 11.32-6 9/16”-18 14.28 13.08-8 3/4”-16 19.00 17.68-10 7/8”-14 22.22 20.68-12 1(1/16)"-12 26.98 25.15 -16 1(5/16)"-12 33.33 31.5 -20 1(5/8)"-12 41.28 39.44 -24 1(7/8)"-12 47.62 45.8-32 2(1/2)"-12 63.5 61.67英制圆柱管螺纹（BSPP）常用规格-4 1/4”-19 13.157 11.55-6 3/8”-19 16.662 14.95-8 1/2”-14 20.955 18.63-12 3/4”-14 26.441 24.11-16 1”-11 33.249 30.29-20 1(1/4)''-11 41.91 38.95英制圆锥管螺纹（BSPT）常用规格基面大径基准距离1/4”-19 13.157 63/8”-19 16.662 6.41/2”-14 20.955 8.23/4”-14 26.441 9.51”-11 33.249 10.41(1/4)''-11 41.91 12.7美制圆锥管螺纹（NPT）1/8”-27 10.24 41/4”-18 13.60 43/8”-18 17.04 4.321/2”-14 21.22 4.483/4”-14 26.57 4.751”-11(1/2)” 33.22 4.61(1/4)”-11.5 41.96 4.832007-4-20 16:33评论(7)3/8-16 0.3643 0.3737 0.3287 0.3331 0.2970 8.40 8.44(0.375-16) 9.2532 9.4920 8.3490 8.4607 7.54387/16-14 0.4258 0.4361 0.3850 0.3897 0.3485 9.83 9.87(0.4375-14) 10.8153 11.0769 9.7790 9.8984 8.85191/2-13 0.4876 0.4985 0.4435 0.4485 0.4041 11.34 11.38(0.50-13) 12.3850 12.6619 11.2649 11.3919 10.26419/16-12 0.5495 0.5609 0.5016 0.5068 0.4587 12.80 12.84(0.5625-12) 13.9573 14.2469 12.7406 12.8727 11.65105/8-11 0.6113 0.6234 0.5589 0.5644 0.5119 14.27 14.32 (0.625-11) 15.5270 15.8344 14.1961 14.3358 13.00233/4-10 0.7353 0.7482 0.6773 0.6832 0.6255 17.28 17.33 (0.750-10) 18.6766 19.0043 17.2034 17.3533 15.88777/8-9 0.8592 0.8731 0.7946 0.8009 0.7368 20.27 20.32(0.875-9) 21.8237 22.1767 20.1828 20.3429 18.71471"-8 0.9830 0.9980 0.9100 0.9168 0.8446 23.22 23.27(1.000-8) 24.9682 25.3492 23.1140 23.2867 21.45281.螺胚直径指滚丝前的尺寸，数值为依经验公式计算而得，在实践中需验证。
公制美制英制螺纹对照表
公制/美制/英制螺纹对照表A型美制螺纹（UNF）常用规格外螺纹螺纹-4 9/16"-19牙 14.28 13.08 -6 11/16''-16 17.46 16.1-8 13/16''-16 20.64 19.28-10 1''-14 25.40 23.57-12 1(3/16)''-12 30.00 28.32 -16 1(7/16)''-12 36.51 34.67 -20 1(11/16)''-12 42.86 41.02C型JIC37度美制UNF螺纹常用规格-4 7/16”-20 11.11 10.03-5 1/2”-20 12.70 11.32-6 9/16”-18 14.28 13.08-8 3/4”-16 19.00 17.68-10 7/8”-14 22.22 20.68-12 1(1/16)"-12 26.98 25.15 -16 1(5/16)"-12 33.33 31.5 -20 1(5/8)"-12 41.28 39.44 -24 1(7/8)"-12 47.62 45.8-32 2(1/2)"-12 63.5 61.67英制圆柱管螺纹（BSPP）常用规格-4 1/4”-19 13.157 11.55-6 3/8”-19 16.662 14.95-8 1/2”-14 20.955 18.63-12 3/4”-14 26.441 24.11-16 1”-11 33.249 30.29-20 1(1/4)''-11 41.91 38.95英制圆锥管螺纹（BSPT）常用规格基面大径基准距离1/4”-19 13.157 63/8”-19 16.662 6.41/2”-14 20.955 8.23/4”-14 26.441 9.51”-11 33.249 10.41(1/4)''-11 41.91 12.7美制圆锥管螺纹（NPT）1/8”-27 10.24 41/4”-18 13.60 43/8”-18 17.04 4.321/2”-14 21.22 4.483/4”-14 26.57 4.751”-11(1/2)” 33.22 4.61(1/4)”-11.5 41.96 4.832007-4-20 16:33评论(7)3/8-16 0.3643 0.3737 0.3287 0.3331 0.2970 8.40 8.44(0.375-16) 9.2532 9.4920 8.3490 8.4607 7.54387/16-14 0.4258 0.4361 0.3850 0.3897 0.3485 9.83 9.87(0.4375-14) 10.8153 11.0769 9.7790 9.8984 8.85191/2-13 0.4876 0.4985 0.4435 0.4485 0.4041 11.34 11.38(0.50-13) 12.3850 12.6619 11.2649 11.3919 10.26419/16-12 0.5495 0.5609 0.5016 0.5068 0.4587 12.80 12.84(0.5625-12) 13.9573 14.2469 12.7406 12.8727 11.65105/8-11 0.6113 0.6234 0.5589 0.5644 0.5119 14.27 14.32 (0.625-11) 15.5270 15.8344 14.1961 14.3358 13.00233/4-10 0.7353 0.7482 0.6773 0.6832 0.6255 17.28 17.33 (0.750-10) 18.6766 19.0043 17.2034 17.3533 15.88777/8-9 0.8592 0.8731 0.7946 0.8009 0.7368 20.27 20.32(0.875-9) 21.8237 22.1767 20.1828 20.3429 18.71471"-8 0.9830 0.9980 0.9100 0.9168 0.8446 23.22 23.27(1.000-8) 24.9682 25.3492 23.1140 23.2867 21.45281.螺胚直径指滚丝前的尺寸，数值为依经验公式计算而得，在实践中需验证。
螺纹基本尺寸对照表要点
英制管螺纹根本尺寸与公差〔牙形角55º〕BSPP英制锥管螺纹根本尺寸与公差〔牙形角55º〕BSPT美制管螺纹根本尺寸与公差〔牙形角60º〕UN(F)公制螺纹根本尺寸与公差(牙形角60º)M55°圆锥管螺纹根本尺寸对照表最新下载-汇兴达55°圆锥管螺纹根本尺寸对照表最新下载-汇兴达55°圆锥管螺纹(BSPT)R66" 11聊城市鑫茂祥管业某某专业经营钢管规格：5mm*1mm—1020mm*200mm合金钢管、外径22mm-127mm冷轧无缝钢管、外径127mm-600mm，壁厚16mm-100mm，外径精度±0.5%,壁厚精度±5%热轧中厚壁无缝钢管、16Mn外径400—1600mm、壁厚20—60mm的大口径厚壁卷管，可定尺到16米与各种规格的无缝方管、异型无缝钢管等.常备钢管种类有:构造用无缝钢管、流体用无缝钢管、液压无缝钢管、电力用无缝钢管、石油输送用无缝钢管、化肥设备用无缝钢管、煤矿用无缝钢管、不锈钢无缝钢管、化工用无缝钢管、纺织机械用无缝钢管、汽车；水利用无缝钢管，精细无缝钢管、光亮无缝钢管、军工医疗用无缝钢管、管道用无缝钢管、支柱用无缝钢管、合金无缝管、高压无缝管、大口径直缝焊管等。
适用于工程、煤矿、纺织、电力、锅炉、机械、军工等各个领域。
公司以良好的信用、优质的产品、雄厚的实力、低廉的价钱享誉全国30多个省、市、自治区、直辖市与国外，产品深得用户依赖。
公司常年销售某某钢铁集团、冶钢集团、某某钢厂、宝钢集团、鞍钢集团、某某大无缝、某某特钢厂、某某钢厂、某某钢厂等各大钢厂生产的各种无缝钢管与合金管。
主营材质：20#、35#、45#、20G、20A、40Mn2、45Mn2、27SiMn、40MnB、20MnVB、20Cr、30Cr、35Cr、40Cr、45Cr、50Cr、 38CrSi、12CrMo 、20CrMo、35CrMo、42CrMo、12CrMoV、12Cr1MoV、38CrMoAL、50CrV、20CrMnSi、30CrMnSi、35CrMnSi、 20CrMnTi、30CrMnTi、12CrNi2、 12CrNi3、12Cr2Ni4、40CrNiMoA、45CrNiMoVA、20G、20MnG、25MnG、12CrMoG、15CrMoG、12Cr2MoG、12Cr1MoVG、12Cr2MoWVTiB、12Cr3MoVSiTiB等实行标准：GB/T8162-99构造管、GB/T8163-99流体管、GB/T3087-99中低压锅炉管、GB/T5310-95高压锅炉管、GB/T6479-2000化肥专用管、27SiMn液压支架管、高压合金管、GB/T9948-85石油裂化管GB9948-88、地质钻探用管YB235-70、汽车半轴套管YB/T5035-96。
英美螺纹资料
Thread1 DefinitionThe diameters, threads per inch (TPI) and thread pitch, etc. are necessary to completely identify a thread. In a shop, specialty gauges are required to accurately gauge or identify threads. In the field, in the absence of these gauges, thread "leaf" gauges can be used to identify the "Threads Per Inch" (TPI) and the thread pitch. On threads you have determined to be straight threads, a caliper can be used to measure the "Outside Diameter of the Male" (ODM) or the "Inside Diameter of the Female" (IDF). A caliper can also be used to take measurements of tapered thread diameters. However, these are more difficult to define because of the taper. Fortunately, there are few tapered threads to deal with and these can usually be identified from the nominal ODM and the TPI.However, identifying the thread may not fully identify what is needed in a matingfitting. The application is the primary limiting factor on the thread type used.We offer products with a wide variety of threads used with hose, pipe andhydraulics.When attempting to choose a fitting, it is always advisable to first identify thethread to which it must connect. This may entail checking with a fitting orequipment manufacturer.The fire hose thread specifications for some local municipal fireequipment and hydrants may vary according to local specifications. Thesecan generally be most easily identified by contacting the local fire departmentresponsible for the hydrant. The most common thread used on fire equipment isNational Standard Thread (NST), also known as National Hose thread (NH).When it is not possible to identify the thread:•1)Determine the number of threads per inch by measuring the distance from peak of thread to peak of thread across the largest number ofwhole threads. Then divide the number of threads by the measurement.(This will provide the TPI).•2) Check to see if the thread is straight or tapered.a) Straight ThreadsMeasure the "Outside Diameter of the Male" (ODM) or the "InsideDiameter of the Female" (IDF), from peak of thread to peak of thread.b) Tapered ThreadsMeasure the "Outside Diameter of the Male" (ODM) at the large endand the small end, or the "Inside Diameter of the Female" (IDF) at thelarge end and the small end, from peak of thread to peak of thread.Then measure the Outside Diameter (OD) of the unthreaded pipe.Once the application and these two pieces of information have been determined, the thread can generally be determined. When in doubt, contact the manufacturer.Straight ThreadMale FemaleTapered ThreadMale FemaleThreading InformationAbbreviationSystem Name CompatibilitySeal Method Male BSPP with Female BSPPWasher Female BSPP with Male BSPP Washer BSPPB ritish S tandard P ipeP arallelFemale BSPP with Male BSPTr Washer Male BSPTr with Female BSPTrThread Male BSPTr with Female BSPP Washer Female BSPTr with Male BSPTr ThreadBSPTrB ritish S tandard P ipeT aperFemale BSPTr not compatible with Male BSPP1"Male NH (NST) with 1" FemaleNH (NST)Washer 1" Female NH (NST) with 1" MaleNH (NST)Washer1" Thread is used on both ¾"hose & 1" hose. CHTAmerican Standard Fire Hose Thread (1" NationalHose Thread is C hemical H ose T hread, also known as Booster Hose Thread)Not compatible with othersystemsMale GHT with Female GHT Washer Female GHT with Male GHTWasherThread is the same for all sizehose.GHT G arden H ose T hreadNot compatible with othersystemsGeneric name for Straight PipeThreadWasherIPS I ron P ipe S traight ThreadSee NPSH for compatibilityJIC J oint I ndustrial C ommitteeUsed with other mating JICthreadsMechanical Male NH (NST) with Female NH(NST)Washer Female NH (NST) with Male NH(NST)Washer NH or NSTAmerican Standard FireHose Coupling Thread (N ational H ose thread alsoknown as N ational S tandard T hreadNot compatible with othersystemsThread pitch and diameters of firethreads may vary according to local and municipal regulations. Male NPT with Female NPT Thread Male NPT with Female NPTF Thread Male NPT with Female NPSMWasher Male NPT with Female NPSH Washer Female NPT with Male NPT Thread Female NPT with Male NPTF Thread NPTAmerican Standard TaperPipe Thread (N ational P ipeT hreadFemale NPT not compatible with Male NPSM or Male NPSH Male NPTF with Female NPTF Thread Male NPTF with Female NPT Thread Male NPTF with Female NPSM Washer Male NPTF with Female NPSHWasher Female NPTF with Male NPTF Thread Female NPTF with Male NPT Thread Female NPTF with Male NPSM orMale NPSHNot CompatibleNPTFAmerican Standard TaperPipe Fuel Dryseal Thread (N ational P ipe T aperedF ine)Note: NPTF with NPTF threads do not require sealant for the initial use. After that, sealant isrequired.Male NPSH with Female NPSHWasher Female NPSH with Male NPSH Washer Female NPSH with Male NPTWasher Female NPSH with Male NPTF Washer NPSHAmerican Standard Straight Pipe for Hose Couplings(N ational P ipe S traightH ose)Female NPSH with Male NPSM Washer Male NPSM with Female NPSMMale NPSM with Female NPSHFemale NPSM with Male NPSM Female NPSM with Male NPT NPSMAmerican Standard Straight Mechanical Joints (N ational P ipe S traightM echanical)Female NPSM with Male NPTFSeal can be either mechanical or washer. Mating fittings must be of same type TIPT T apered I ron P ipe T hread Generic name for Tapered PipeThreadThreadThread DimensionsNominal Dimensions of Standard ThreadsNPTNPSH NPSMSizePipeO. D. TPI TPI ODM(Max)IDF (Min)TPIODM(Max)IDF(Min)1/8" .405 27 - - -270.3970.358 1/4" .504 18 - - -180.5260.468 3/8" .675 18 - - -180.6620.603 1/2" .840 14 140.82480.7395140.8230.747 3/4" 1.050 14 14 1.03530.950014 1.0340.958 1"1.315 11.511.51.29511.192111.51.2931.2011-¼" 1.660 11.511.51.63991.536911.51.6381.546 1-½" 1.900 11.511.51.87881.775811.51.8771.785 2"2.375 11.511.52.35282.249811.52.3512.2592-½" 2.875 8 - - - 8 2.8412.708 3" 3.500 8 - - - 8 3.4673.334 4" 4.500 8 - - - 8 4.4664.333 5" 5.563 8 - - - 8 5.5285.395 6" 6.625 8 - - - 86.5856.4528"8.625 8 - - - - - -10" 10.750 8 - - - - - - 12" 12.750 8 - - - - - -ODM = Outside Diameter of Male IDF = Inside Diameter of FemaleTPI = Threads per Inch GHT (¾") = 1.0625 ODM, 11-½ TPINH (NST) BSPP (Parallel)BSPTr (Tapered) SizePipe O. D.TPIODM(Max)IDF(Min)TPIODM(Max)IDF(Min)TPI 1/8" .405 - - - -0.3830.33728 1/4" .504 - - - -0.5160.45019 3/8" .675- - - -0.6560.588191/2" .840 - - - -0.8250.733143/4" 1.050 8 1.3751.2246- 1.0410.950141" 1.315 8 1.3751.224611 1.3091.193111-¼" 1.660 - - - - 1.6501.534111-½" 1.900 9 1.9901.857711 1.8821.766112" 2.375 - - - - 2.3472.231112-½" 2.875 7.5 3.0682.910411 2.9602.844113" 3.500 6 3.6233.530611 3.4603.344114" 4.500 4 5.010 4.711111 4.4504.334114-½" - 4 5.760 5.4611-- - -5" 5.563 4 6.2605.960211 5.4505.359116" 6.625 4 7.0256.725211 6.4506.35911ODM = Outside Diameter of MaleIDF = Inside Diameter of FemaleTPI = Threads per InchGHT (¾") = 1.0625 ODM, 11-½ TPINOTE: Female NPT (Tapered Pipe) thread is not available onhose swivel nuts.Normal Engagement Lengthof NPT Thread in Inches ("A") *Size 1/8" 1/4" 3/8"1/2"3/4"1" 1-¼"1-½"2"Length 1/4" 3/8" 3/8"1/2"9/16"11/16"11/16"11/16"3/4"Size 2-½" 3" 4" 5" 6" 8" 10" 12"Length15/16" 1" 1-1/8"1-1/4"1-5/16"1-7/16"1-5/8"1-3/4"* Dimensions given do not allow for variations in tapping or threadingThread Sealing TipsThread Seal Type• A seal is obtained by applying asealant to the male thread beforeengaging.•The sealant is used to prevent spiralleakage.•Thread tape or paste is the preferredsealant in this type of application.Washer Seal Type• A seal is obtained when the malethread is tightened down onto thewasher of the female assembly.•The washer should be inspectedregularly and replaced as needed toprevent leakage.Mechanical Seal Type• A seal is obtained through metal tometal contact or metal to sealcontact, for example JIC couplingshave a metal to metal seal. EZ-BossGround Joint couplings have a metalto seal contact (shown at left).•The couplings should be retightenedas needed to prevent leakage.More Thread Sealing Tips...Sealing NPT threads can be an exasperating experience if certain techniquesare not followed. The following tips will help alleviate many common problemsin thread sealing:• 1. Always use some type of sealant (tape or paste) andapply sealant to male threadonly. If using a hydraulic sealant,allow sufficient curing timebefore system is pressurized. • 2. When using tape sealant, wrap the threads in a clockwisemotion starting at the first threadand, as layers are applied, worktowards the imperfect(vanishing) thread. If the systemthat the connection being madeto cannot tolerate foreign matter(i.e. air systems), leave the firstthread exposed and apply thetape sealant as outlined above. • 3. When using paste sealant, • 6. For sizes 2" and below, tape or paste usually performssatisfactorily. When using threadtape, four wraps (covering allnecessary threads) is usuallysufficient.•7. For sizes 2-½" and above, thread paste is recommended. Ifthread tape is used, eight wraps(covering all necessary threads)is usually sufficient. Apply morewraps if necessary.•8. For stubborn to seal threads, apply a normal coating of threadpaste followed by a normal layerof thread tape.•9. For extremely stubborn to seal threads, apply a normalapply to threads with a brush,using the brush to work thesealant into the threads. Applyenough sealant to fill in all thethreads all the way around.• 4. When connecting onestainless steel part to anotherstainless steel part that willrequire future disassembly, usea thread sealant that is designedfor stainless steel. This stainlesssteel thread sealant is alsouseful when connectingaluminum to aluminum thatneeds to be disconnected in thefuture. These two materials galleasily, and if the correct sealantis not used, it can be next toimpossible to disassemble.• 5. When connecting parts made of dissimilar metals (i.e. steel &aluminum), standard tape orpaste sealant usually performssatisfactorily.coating of thread paste followedby a single layer of gauzebandage followed by a normallayer of thread tape.Caution!When this procedure is done,the connection becomespermanent. Extreme measureswill be necessary to disconnectthese components. All othermeasures to seal the threadsshould be explored prior to theuse of this technique.•10. Over-tightening threads can be just as detrimental asinsufficient tightening. For sizes2" and below, hand tighten thecomponents and, with a wrench,tighten 3 full turns. for sizes 2-½"and above, hand tighten thecomponents and, with a wrench,tighten 2 full turns.2 Pipe Thread StandardsTwo common pipe thread standards exist:•National Pipe Thread (NPT) - a tapered thread•National Standard Free-Fitting Straight Mechanical Pipe Thread (NPSM) - a straight threadLess common standards also exist:•Garden Hose Thread (GHT)•Fire Hose Coupling (NST)•British Standard Taper Pipe Thread (BSPT)Female NPT threads can be designated as "FPT" and male NPT threads can be designated as "MPT." I have also seen female NPT threads designated as "FNPT" and male as "MNPT".Straight Versus Tapered ThreadsThreaded pipe can be connected to join things together, which does not necessarily produce a leakproof seal, or they can be joined and sealed.Straight threads only provide a mechanical junction. They don't really seal.Tapered threads both join and seal. The deeper you drive them, the tighter the seal.Pipe Thread TapeWhenever you want a good seal when screwing together pipes and fittings, use pipe thread tape. This is usually made of PTFE, the most famous brand of which is Teflon.In addition to sealing, pipe thread tape also lubricates the joint, which:•makes it easier to tighten it•makes it easier to disassemble the joint in the future•reduces/eliminates thread galling [Thread galling is when threads weld themselves together. This is more common with pipes and fasteners made fromalloys that protect themselves from corrosion by developing their own oxidesurface film, like aluminum and stainless steel.Standard Pipe SizesPipe sizes do not refer to any physical dimension of modern pipe. If you measure a piece of 1/4" NPT pipe, you will have a hard time finding anything there that measures 1/4".Historical note:•The sizes derive from the days when pipes were made of iron, pipe walls were rather thick, and the internal diameter (ID) was standardized. At that time, if you specified a 1/2" pipe, it had an internal diameter of 1/2", and an outer diameter that depended on the thickness of the wall.•Nowadays, the standards measure the threaded part of the pipe, the outer diameter (OD). This lets thin-wall and thick-wall pipe use the same fittings.•But we kept the same names, so when you say 1/2" pipe, you get a pipe whose outer diameter is the same as that of an old-fashioned iron pipe whose inner diameter was 1/2".In order to get the right size, you should measure the outer diameter (OD) of the pipe, and look it up in a table to find out what it is officially called. It's also a good idea to measure the threads per inch (TPI). The combination of OD and TPI provide positive identification of standard pipe sizes.Pipe Thread Size Threads per Inch OD Fraction(approximate)OD Decimal(actual)Normal depthfor tight joint1/16" 27 5/16" 0.3125" 0.2611" 1/8" 27 13/32" 0.405" 0.2639" 1/4" 18 35/64" 0.540" 0.4018" 3/8" 18 43/64" 0.675" 0.4078" 1/2" 14 27/32" 0.840" 0.5337" 3/4" 14 1-3/64 1.050" 0.5457" 1" 11-1/2 1-5/16" 1.315" 0.6828" 1-1/4" 11-1/2 1-21/32" 1.660" 0.7068" 1-1/2" 11-1/2 1-29/32" 1.900" 0.7235" 2" 11-1/2 2-3/8" 2.375" 0.7565" 2-1/2" 8 2-7/8" 2.875" 1.1375" 3" 8 3-1/2" 3.5" 1.2000" 3-1/2" 8 4" 4.0" 1.2500" 4" 8 4-1/2" 4.5" 1.3000"3,。
美制迫牙丝攻钻孔径／英制螺纹／针车用螺纹
纹
下孔径 下限 1.182 1.474 1.756 2.025 2.271 2.551 2.82 3.404 3.963 4.496
3\8-24
7\16-20 1\2-20 9\16-18 5\8-18 3\4-16 7\8-14 1\8-12 1-1\8-12 1-1\4-12 1-3\8-12 1-1\2-12
1.25 1.305 1.182
G4－G6 G7－G8 G9
1.55 1.612 1.474 M1.0*0.25
0.86
5.5 5.588
5.36
6.9 7.035
6.782
8.5
9.9 11.5 12.9 14.5 17.5 20.5 23.2 26.5
8.636
10.033 11.607 13.081 14.681 17.678 20.675 23.571 26.746
8.382
9.729 11.329 12.75 14.35 17.32 20.27 23.11 26.28
针车用螺纹
规格
滚造径
SW1\8-40 2.735--2.688
SM1\8-44 2.769--2.722
美制细螺纹
公制迫牙丝攻钻孔径
规格(丝牙外 径）
标准径
最大
最小
规格
精度等级
7－G8 NO.172(1.854) NO.264(2.134) NO.356(2.515) NO.448(2.345) NO.544(3.175) NO.640(3.505) NO.836(4.166) NO.1032(4.326) NO.1228(5.846) 1\4-28 5\16-24
1.51
1.53
3.5
国外常用螺纹对照表
国外常用②我国的60°圆锥管螺纹GB/T12716-1991与之等效。
③ACME螺纹包括一般用途的和定心的两种配合的梯形螺纹，其中一般用途者与我国标准GB/T5796-1986规定的梯形螺纹的性能相类同。
圆锥管螺螺距用每英寸的牙数来表示，如：每英寸11牙，则螺距=25.4/11=2.309mm。
表中螺距单位为每英寸牙数。
钻孔直径为攻丝推荐钻孔尺寸，单位为毫米。
2螺纹标准NPT，PT，G都是管螺纹．NPT 是National (American) Pipe Thread 的缩写，属于美国标准的60 度锥管螺纹，用于北美地区．国家标准可查阅GB/T12716-1991PT 是Pipe Thread 的缩写，是55 度密封圆锥管螺纹，属惠氏螺纹家族，多用于欧洲及英联邦国家．常用于水及煤气管行业，锥度规定为1:16．国家标准可查阅GB/T7306-2000G 是55 度非螺纹密封管螺纹，属惠氏螺纹家族．标记为G 代表圆柱螺纹．国家标准可查阅GB/T7307-2001另外螺纹中的1/4、1/2、1/8 标记是指管子的通径，单位是英寸．行内人通常用分来称呼螺纹尺寸，一寸等于8分，1/4 寸就是2分，如此类推．G 好像就是管螺纹的统称(Guan)，55，60度的划分属于功能性的，俗称管圆。
即螺纹由一圆柱面加工而成。
ZG俗称管锥，即螺纹由一圆锥面加工而成，一般的水管接头都是这样的Rc表示圆锥内螺纹ZG表示锥管螺纹，3/4"表示英寸的标注,就是3/4寸圆锥管螺纹，《五金手册》上有。
准确的来讲它的内径是19.05毫米，但这是老标准，现在已经不用了。
现在的国标规定ZG3/4〃螺纹内径是20毫米。
它的表示方法应该是：ZG3/4〃。
其中（〃）是英寸的代表符号。
一英寸等于25.4毫米。
一英寸等于8英分。
3/4的来历是6/8=3/4。
俗称6分。
同样ZG1/2〃螺纹的管子内径≈15毫米。
俗称4分。
ZG1〃螺纹的管子内径≈25毫米。