螺纹，做阀门的天天打交道，国内的国外的，公制的英制的，直的锥的，密封的非密封的，内的外的，55度的60度的。总之常常被搞乱，傻傻分不清那些螺纹。今天，就和良工阀门一起来理一理这些螺纹吧！

　　Threads, valves that we deal with every day, domestic and foreign, metric and imperial, straight cone, sealed and unsealed, internal and external, 55 degrees and 60 degrees. In short, they are often confused and can't distinguish those threads clearly. Today, let's work together with Lianggong Valve to sort out these threads!

　　（一）NPT是一般用途的美国标准锥管螺纹，牙型角为60°PT牙为英制锥螺纹，牙型角为55°，密封中常用。英制管螺纹是细牙螺纹，因为粗牙螺纹的牙深大，会严重的降低所切螺纹外径管子的强度。PF牙是管用平行螺纹。G 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，G是管螺纹的统称(Guan)，55、60度的划分属于功能性的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，老国标标注为Rc公制螺纹用螺距来表示，美英制螺纹用每英寸内的螺纹牙数来表示，这是它们的区别，公制螺纹是60度等边牙型，英制螺纹是等腰55度牙型，美制螺纹60度。公制螺纹用公制单位，美英制螺纹用英制单位。管螺纹主要用来进行管道的连接，其内外螺纹的配合紧密，有直管与锥管两种。公称直径是指所连接的管道直径，显然螺纹大径比公称直径大。1/4，1/2，1/8是英制螺纹的公称直径，单位是英寸。

　　（1） NPT is a general purpose American standard taper pipe thread with a profile angle of 60 °. PT thread is an imperial taper thread with a profile angle of 55 °, which is most commonly used in sealing. British pipe threads are fine thread threads, as the large thread depth of coarse thread threads can significantly reduce the strength of the pipe with the outer diameter of the cut thread. PF teeth use parallel threads. G is a 55 degree non threaded sealed pipe thread, belonging to the Wyeth thread family. The symbol G represents cylindrical thread, G is the general term for pipe thread (Guan), and the division of 55 and 60 degrees belongs to functional ZG, commonly known as pipe cone, which means that the thread is processed from a conical surface. Generally, water pipe joints are like this. The old national standard is marked as Rc metric thread, which is represented by pitch, and American British thread, which is represented by the number of threads per inch. This is their biggest difference. Metric thread is a 60 degree equilateral profile, British thread is an isosceles 55 degree profile, and American thread is 60 degrees. Metric threads are measured in metric units, while American and British threads are measured in imperial units. Pipe threads are mainly used for connecting pipelines, with tight fit between internal and external threads, available in two types: straight pipes and tapered pipes. The nominal diameter refers to the diameter of the connected pipeline, and obviously the thread diameter is larger than the nominal diameter. 1/4, 1/2, and 1/8 are the nominal diameters of imperial threads, measured in inches.

　　（二）1、英寸制统一螺纹在英寸制广泛采用，该类螺纹分三个系列：粗牙系列UNC，细牙系列UNF，特细牙系列UNFF，外加一个定螺距系列UN。标注方法：螺纹直径—每英寸牙数系列代号—精度等级示例：粗牙系列 3/8—16UNC—2A细牙系列 3/8—24UNF—2A特细牙系列 3/8—32UNFF—2A定螺距系列 3/8—20UN—2A位数字3/8表示螺纹外径，单位为英寸，转换为米制单位mm要乘以25.4，即3/8×25.4=9.525mm；第二、三位数字16、24、32、20为每英寸牙数(在25.4mm长度上的牙数)；第三位以后的文字代号UNC、UNF、UNFF、UN为系列代号，两位2A为精度等级。

　　（2） 1. Inch based unified threads are widely used in inch based countries. This type of thread is divided into three series: coarse thread series UNC, fine thread series UNF, ultra-fine thread series UNFF, and an additional fixed pitch series UN. Annotation method: Thread diameter - Number of teeth per inch series code - Accuracy level Example: Coarse thread series 3/8-16UNC -2A Fine thread series 3/8-24UNF -2A Extra fine thread series 3/8-32UNFF -2A Fixed pitch series 3/8-20UN -2A The first digit 3/8 represents the outer diameter of the thread, measured in inches. When converted to metric units in millimeters, it needs to be multiplied by 25.4, which is 3/8 × 25.4=9.525mm; The second and third digits 16, 24, 32, and 20 represent the number of teeth per inch (teeth on a length of 25.4mm); The text codes UNC, UNFPA, AFFF, and UN after the third digit represent the series code, and the last two digits 2A represent the accuracy level.

　　2 、55°圆柱管螺纹的转化55°圆柱管螺纹，来源于英寸制系列，但米制和英寸制均广泛采用，用于输送液体经、气体和安装电线的管接头与管子的联接，然而，各国的代号不同，应按下表(对照表)中的国外代号转化为我国代号，现将各国的55°圆柱管螺纹代号列于下表。国别 代号G日本G、PF英国BSP、BSPP法国G德国R(内螺纹)、K(外螺纹)前苏联 G、TPУБISO Rp

　　2. The conversion of 55 ° cylindrical pipe thread to 55 ° cylindrical pipe thread is derived from the inch series, but both metric and inch systems are widely used in countries for connecting pipe joints and pipes used for transporting liquids, gases, and installing wires. However, the codes of different countries are different, and the foreign codes in the following table (reference table) should be converted to Chinese codes. The 55 ° cylindrical pipe thread codes of each country are listed in the table below. Country code: China G Japan G, PF UK BSP, BSPP France G Germany R (internal thread), K (external thread) Former Soviet Union G, TP УБ ISO Rp

　　3、55°圆锥管螺纹的转化55°圆锥管螺纹，是指螺纹的牙型角为55°、螺纹具有1：16的锥度。该系列螺纹在世界上应用广泛，它的代号，各国规定不同，见下表。按下表中的国外代号转化为我国代号。国别 代号ZG、R(外螺纹)英国BSPT、R(外螺纹)、Rc(内螺纹)法国G(外螺纹)、R(外螺纹)德国R(外螺纹)日本PT、RISO R(外螺纹)、Rc(内螺纹)

　　3. Conversion of 55 ° Conical Pipe Thread: 55 ° Conical Pipe Thread refers to a thread with a tooth profile angle of 55 ° and a taper of 1:16. This series of threads is widely used in the world, and its code varies from country to country, as shown in the table below. Convert the foreign codes in the table to Chinese codes. Country code: China ZG, R (external thread), UK BSPT, R (external thread), Rc (internal thread), France G (external thread), R (external thread), Germany R (external thread), Japan PT, RISO R (external thread), Rc (internal thread)

　　4、60°圆锥管螺纹的转化60°圆锥管螺纹是指牙型角为60°、螺纹锥度为1：16的管螺纹，此系列螺纹在我国机床行业和美国、前苏联应用。它的代号，我国过去规定为K，后来规定为Z，现在改为NPT。螺纹代号对照表见下表。国别 代号Z(旧)NPT(新)美国NPT苏联B

　　4. Conversion of 60 ° Conical Pipe Thread: 60 ° Conical pipe thread refers to pipe threads with a tooth angle of 60 ° and a thread taper of 1:16. This series of threads is used in China's machine tool industry, as well as in the United States and the former Soviet Union. Its code name was previously designated as K in China, later designated as Z, and now changed to NPT. The comparison table of thread codes is shown in the following table. Country code: China Z (old) NPT (new) US NPT Soviet B

　　三、螺纹分类依螺纹用途不同可分为：1、国际公制标准螺纹(International

　　3、 Thread classification can be divided into: 1. International metric standard thread (International metric standard thread)

　　Metric Thread System)我国标准CNS采用之螺纹。牙顶为平面，易於车削，牙底则为圆弧形，以增加螺纹强度。螺纹角为60 度，规格以M表示。公制螺纹可分粗牙及细牙二种。表示法如M8x1.25。(M：代号、8：公称直径、1.25：螺距)。

　　Metric Thread System is a thread used in China's national standard CNS. The tooth crest is flat and easy to turn, while the tooth base is arc-shaped to increase thread strength. The thread angle is 60 degrees, and the specification is represented by M. Metric threads can be divided into two types: coarse threads and fine threads. Represented as M8x1.25. (M: code, 8: nominal diameter, 1.25: pitch).

　　2、美国标准螺纹(American StandardThread)螺纹顶部与根部皆为平面，强度较佳。螺纹角亦为60度，规格以每英寸有几牙表示。此种螺纹可分为粗牙(NC)；细牙(NF)；特细牙(NEF)三级。表示法如1/2-10NC。(1/2：外径；10：每寸牙数；NC代号)。

　　2. The top and root of American Standard Thread threads are flat, providing better strength. The thread angle is also 60 degrees, and the specification is expressed as the number of teeth per inch. This type of thread can be classified as coarse thread (NC); Fine teeth (NF); Very fine teeth (NEF) grade three. Represented as 1/2-10NC. (1/2: outer diameter; 10: number of teeth per inch; NC code).

　　3、统一标准螺纹(Unified Thread)由美国、英国、加拿大三国共同制订，为目前常用之英制螺纹。螺纹角亦为60度，规格以每英寸有几牙表示。此种螺纹可分为粗牙(UNC)；细牙(UNF)；特细牙(UNEF)。表示法如1/2-10UNC。(1/2：外径；10：每寸牙数；UNC代号)

　　3. The Unified Thread was jointly developed by the United States, the United Kingdom, and Canada, and is currently the commonly used British thread. The thread angle is also 60 degrees, and the specification is expressed as the number of teeth per inch. This type of thread can be classified as coarse thread (UNC); Fine teeth (UNF); Ultra fine teeth (UNEF). Represented as 1/2-10UNC. (1/2: outer diameter; 10: number of teeth per inch; UNC code)

　　4、V形螺纹(Sharp V Thread)顶部与根部均成尖状，强度较弱，亦坏不常使用。螺纹角为60 度。

　　4. Sharp V Thread has a pointed shape at both the top and root, with weak strength and is not commonly used. The thread angle is 60 degrees.

　　5、惠式螺纹(Whitworth Thread)英国标准采用之螺纹。螺纹角为55度，表示符号为”W”。适用於滚压法制造。表示法如W1/2-10。(1/2：外径；10：每寸牙数；W代号)。

　　5. Whitworth Thread is a thread used in the British National Standard. The thread angle is 55 degrees, indicated by the symbol "W". Suitable for rolling method manufacturing. Represented as W1/2-10. (1/2: outer diameter; 10: number of teeth per inch; W code).

　　6、圆螺纹(Knuckle Thread)为德国DIN所定之标准螺纹。适用於灯泡、橡皮管之连接。表示符号为”Rd”。

　　6. Knuckle Thread is a standard thread specified by DIN in Germany. Suitable for connecting light bulbs and rubber tubes. The symbol is' Rd '.

　　7、管用螺纹(Pipe Thread)为防止泄漏用的螺纹，经常用於气体或液体之管件连结。螺纹角为55度，可分为直管螺纹代号为”P.S.、N.P.S.”和斜管螺纹代号为”N.P.T.”，其锥度为1：16，即每尺3/4 寸。

　　7. Pipe Thread is a thread used to prevent leakage and is often used to connect gas or liquid fittings. The thread angle is 55 degrees and can be divided into straight pipe threads with the code "P S. The code for "N.P.S." and diagonal pipe threads is "N P.T.”， Its taper is 1:16, which is 3/4 inch per foot.

　　8、方螺纹(Square Thread)传动效率大，仅次於滚珠螺纹，而磨损后无法用螺帽调整，为其缺点。一般用於虎钳之螺杆及起重机之螺纹。

　　8. Square Thread has a high transmission efficiency, second only to ball threads, and its disadvantage is that it cannot be adjusted with a nut after wear. Generally used for the screw of pliers and the thread of cranes.

　　9、梯形螺纹(Trapezoidal Thread)又称爱克姆螺纹。传动效率较方螺纹稍小，但磨损后可用螺帽调整。公制之螺纹角为30 度、英制之螺纹角为29度。一般用於车床之导螺杆。表示符号为”Tr”。

　　9. Trapezoid Thread, also known as Aikem Thread. The transmission efficiency is slightly lower than that of square threads, but it can be adjusted with a nut after wear. The thread angle of the metric system is 30 degrees, and the thread angle of the imperial system is 29 degrees. Generally used for lead screws in lathes. The symbol is "Tr".

　　10、锯齿形螺纹(Buttress Thread)又称斜方螺纹，只适於单方向传动。如螺旋千斤顶、加压机等。表示符号为”Bu”。

　　10. Buttress Thread, also known as diagonal thread, is only suitable for one-way transmission. Such as screw jacks, pressure machines, etc. The symbol is "Bu".

　　11、滚珠螺纹为传动效率之螺纹，其制造困难，成本极高，乃用於精密之机械上。如数控工具机之导螺杆。英制螺栓之表示法：LH 2N 5/8 × 3 - 13UNC-2A(1)LH为左螺纹 (RH为右螺纹，可省略)。(2)2N双线螺纹。(3)5/8 英制螺纹，外径 5/8”。(4)3 螺栓长度3” 。(5)13 螺纹每寸牙数13 牙。(6)UNC统一标准螺纹粗牙。(7)2级配合，外螺纹(3：紧配合；2：中配合；1：松配合) A:外螺纹(可省略) B:内螺纹英制螺纹：英制螺纹之大小，通常以螺纹上每寸长度有若干螺纹数表示，简称为「每寸牙数」，恰等於螺距之倒数。例如每寸8牙之螺纹，其螺距为1/8 寸。

　　11. Ball screw thread is the most efficient thread for transmission, but its manufacturing is difficult and the cost is extremely high, so it is used in precision machinery. Like the lead screw of a CNC machine tool. The representation of British bolts: LH 2N 5/8 × 3-13UNC-2A (1) LH is the left thread (RH is the right thread, can be omitted). (2) 2N double thread. (3) 5/8 inch thread, outer diameter 5/8 ". (4) 3 bolts with a length of 3 inches. (5) 13 threads per inch with 13 teeth. (6) UNC Unified Standard Thread Coarse Thread. (7) 2-level fit, external thread (3: tight fit; 2: medium fit; 1: loose fit) A: external thread (can be omitted) B: internal thread British thread: the size of the British thread is usually represented by the number of threads per inch of length on the thread, abbreviated as "number of threads per inch", which is exactly the reciprocal of the pitch. For example, a thread with 8 teeth per inch has a pitch of 1/8 inch.

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