螺紋，做閥門的天天打交道，國內的國外的，公制的英制的，直的錐的，密封的非密封的，內的外的，55度的60度的。總之常常被搞亂，傻傻分不清那些螺紋。今天，就和良工閥門一起來理一理這些螺紋吧！

　　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是一般用途的美國標準錐管螺紋，牙型角為60°PT牙為英制錐螺紋，牙型角為55°，密封中最常用。英制管螺紋是細牙螺紋，因為粗牙螺紋的牙深大，會嚴重的降低所切螺紋外徑管子的強度。PF牙是管用平行螺紋。G 是55度非螺紋密封管螺紋，屬惠氏螺紋家族．標記為 G代表圓柱螺紋，G是管螺紋的統稱(Guan)，55、60度的劃分屬于功能性的ZG俗稱管錐，即螺紋由一圓錐面加工而成，一般的水管接頭都是這樣的，老國標標注為Rc公制螺紋用螺距來表示，美英制螺紋用每英寸內的螺紋牙數來表示，這是它們最大的區別，公制螺紋是60度等邊牙型，英制螺紋是等腰55度牙型，美制螺紋60度。公制螺紋用公制單位，美英制螺紋用英制單位。管螺紋主要用來進行管道的連接，其內外螺紋的配合緊密，有直管與錐管兩種。公稱直徑是指所連接的管道直徑，顯然螺紋大徑比公稱直徑大。1/4，1/2，1/8是英制螺紋的公稱直徑，單位是英寸。

　　（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、英寸制統一螺紋在英寸制國家廣泛采用，該類螺紋分三個系列：粗牙系列UNC，細牙系列UNF，特細牙系列UNFF，外加一個定螺距系列UN。標注方法：螺紋直徑—每英寸牙數系列代號—精度等級示例：粗牙系列 3/8—16UNC—2A細牙系列 3/8—24UNF—2A特細牙系列 3/8—32UNFF—2A定螺距系列 3/8—20UN—2A第一位數字3/8表示螺紋外徑，單位為英寸，轉換為米制單位mm要乘以25.4，即3/8×25.4=9.525mm；第二、三位數字16、24、32、20為每英寸牙數(在25.4mm長度上的牙數)；第三位以后的文字代號UNC、UNF、UNFF、UN為系列代號，最后兩位2A為精度等級。

　　（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°圓柱管螺紋的轉化55°圓柱管螺紋，來源于英寸制系列，但米制和英寸制國家均廣泛采用，用于輸送液體經、氣體和安裝電線的管接頭與管子的聯接，然而，各國的代號不同，應按下表(對照表)中的國外代號轉化為我國代號，現將各國的55°圓柱管螺紋代號列于下表。國別 代號中國G日本G、PF英國BSP、BSPP法國G德國R(內螺紋)、K(外螺紋)前蘇聯 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°圓錐管螺紋的轉化55°圓錐管螺紋，是指螺紋的牙型角為55°、螺紋具有1：16的錐度。該系列螺紋在世界上應用廣泛，它的代號，各國規定不同，見下表。按下表中的國外代號轉化為我國代號。國別 代號中國ZG、R(外螺紋)英國BSPT、R(外螺紋)、Rc(內螺紋)法國G(外螺紋)、R(外螺紋)德國R(外螺紋)日本PT、RISO R(外螺紋)、Rc(內螺紋)

　　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°圓錐管螺紋的轉化60°圓錐管螺紋是指牙型角為60°、螺紋錐度為1：16的管螺紋，此系列螺紋在我國機床行業和美國、前蘇聯應用。它的代號，我國過去規定為K，后來規定為Z，現在改為NPT。螺紋代號對照表見下表。國別 代號中國Z(舊)NPT(新)美國NPT蘇聯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、螺紋分類依螺紋用途不同可分為：1、國際公制標準螺紋(International

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

　　Metric Thread System)我國國家標準CNS采用之螺紋。牙頂為平面，易於車削，牙底則為圓弧形，以增加螺紋強度。螺紋角為60 度，規格以M表示。公制螺紋可分粗牙及細牙二種。表示法如M8x1.25。(M：代號、8：公稱直徑、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、美國標準螺紋(American StandardThread)螺紋頂部與根部皆為平面，強度較佳。螺紋角亦為60度，規格以每英寸有幾牙表示。此種螺紋可分為粗牙(NC)；細牙(NF)；特細牙(NEF)三級。表示法如1/2-10NC。(1/2：外徑；10：每寸牙數；NC代號)。

　　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、統一標準螺紋(Unified Thread)由美國、英國、加拿大三國共同制訂，為目前常用之英制螺紋。螺紋角亦為60度，規格以每英寸有幾牙表示。此種螺紋可分為粗牙(UNC)；細牙(UNF)；特細牙(UNEF)。表示法如1/2-10UNC。(1/2：外徑；10：每寸牙數；UNC代號)

　　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形螺紋(Sharp V Thread)頂部與根部均成尖狀，強度較弱，亦壞不常使用。螺紋角為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、惠式螺紋(Whitworth Thread)英國國家標準采用之螺紋。螺紋角為55度，表示符號為”W”。適用於滾壓法制造。表示法如W1/2-10。(1/2：外徑；10：每寸牙數；W代號)。

　　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、圓螺紋(Knuckle Thread)為德國DIN所定之標準螺紋。適用於燈泡、橡皮管之連接。表示符號為”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、管用螺紋(Pipe Thread)為防止泄漏用的螺紋，經常用於氣體或液體之管件連結。螺紋角為55度，可分為直管螺紋代號為”P.S.、N.P.S.”和斜管螺紋代號為”N.P.T.”，其錐度為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、方螺紋(Square Thread)傳動效率大，僅次於滾珠螺紋，而磨損后無法用螺帽調整，為其缺點。一般用於虎鉗之螺桿及起重機之螺紋。

　　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、梯形螺紋(Trapezoidal Thread)又稱愛克姆螺紋。傳動效率較方螺紋稍小，但磨損后可用螺帽調整。公制之螺紋角為30 度、英制之螺紋角為29度。一般用於車床之導螺桿。表示符號為”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、鋸齒形螺紋(Buttress Thread)又稱斜方螺紋，只適於單方向傳動。如螺旋千斤頂、加壓機等。表示符號為”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、滾珠螺紋為傳動效率最好之螺紋，其制造困難，成本極高，乃用於精密之機械上。如數控工具機之導螺桿。英制螺栓之表示法：LH 2N 5/8 × 3 - 13UNC-2A(1)LH為左螺紋 (RH為右螺紋，可省略)。(2)2N雙線螺紋。(3)5/8 英制螺紋，外徑 5/8”。(4)3 螺栓長度3” 。(5)13 螺紋每寸牙數13 牙。(6)UNC統一標準螺紋粗牙。(7)2級配合，外螺紋(3：緊配合；2：中配合；1：松配合) A:外螺紋(可省略) B:內螺紋英制螺紋：英制螺紋之大小，通常以螺紋上每寸長度有若干螺紋數表示，簡稱為「每寸牙數」，恰等於螺距之倒數。例如每寸8牙之螺紋，其螺距為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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