螺纹标准

Thread andEnd ConnectionIdentification Guide3ContentsIntroductionThread and End Connection Terminology. . . . 4General Terminology. . . . . . . . . . . . . . . . . . 5Step-by-Step IdentificationProcedure for Threadsand End Connections. . . . . . . . . . . . . . 6Thread IdentificationReference Tables. . . . . . . . . . . . . . . . . . 12Tapered Threads. . . . . . . . . . . . . . . . . . 20End Connections That Use:Tapered Threads. . . . . . . . . . . . . . . . . . . . . 22Straight Threads. . . . . . . . . . . . . . . . . . 26End Connections That Use:Unified Screw Threads. . . . . . . . . . . . . . . . . 28ISO 228/1 Threads. . . . . . . . . . . . . . . . . . . 35Metric (ISO 261) Threads. . . . . . . . . . . . . . 42NPSM Threads. . . . . . . . . . . . . . . . . . . . . . 49AppendixEnd Connection to Thread Matrix. . . . . . . . 50Thread to End Connection Matrix. . . . . . . . 51Thread Identification Tools. . . . . . . . . . . . . 52Glossary. . . . . . . . . . . . . . . . . . . . . . . . . . . 534IntroductionThread andEnd Connection TerminologyStandards are used to help identify threads and endconnections. We will use the following definitions inthismanual:Thread StandardAspecific reference to a formal standard (forexample,ANSI/ASME B1.1, DIN 2999, orISO261) whichdescribes thread form, including a thread’s angle,pitch, and diameter.End Connection StandardAspecific reference to a national standard (suchasDIN 3852 or JIS PT) or industry-groupstandard (suchas SAE J512) which describes anend connection’scomponents, sealarea, geometry, and nominal sizes.Thread standards are usually referenced in the endconnection standard.Thread Standards andEnd Connection StandardsMany mechanical end connections have threads.Therefore, thread standards can be used to helpdefine end connection standards.PitchFor the purposes of this guide, pitch refers to threadsper inch, instead of the distance between the threads,forfractional screw threads and pipe threads. Forall metric screw threads, pitch refers to the distancebetween adjacent threads.5General TerminologyGeneral terms and characteristics, which apply to allend connection threads, are shown below for bothmale and female threads.Threads1.Crest5.Thread Flank Angle2.Root6.Taper Angle3.Flank7.Male Thread OD4.Pitch (Metric)8.Female Thread IDEnd Connections1.Body Size2.Shoulder3.FaceMaleFemaleEnd Connection123512346786Step-by-Step IdentificationProcedure for Threadsand End ConnectionsSTEP1:Determine if the thread is tapered orstraight (parallel).STEP2:Measure the thread diameter.STEP3:Determine the thread pitch.STEP4:Determine the thread standard.STEP5:Identify the end connection.NOTE:Even experienced workers sometimeshave difficulty identifying threads,regardless of their thread identificationprocedure and the quality of their gauges.DetailsSTEP1:Determine if the thread is tapered or straight (parallel).Use a caliper to measure the nominal male or femalethread crest-to-crest diameter on the first, fourth, andlast full threads. (See Figure 1.)If the diameters increase for a male end ordecrease for a female end, the thread is tapered.If all the diameters are the same, the thread isFigure 1.Measuring Crest-to-Crest Thread DiametersLast4th1st7IDENTIFICATIONstraight (parallel).STEP2:Measure the thread e a caliper to measure the nominal male orfemalethread diameter from crest-to-crest. (See Figure 2.)Measure the fourth or fifth full thread. Measure any full thread.The diameter measurement obtained in this step maynot be exactly the same as the listed nominal size forthe given thread. The main reason for this variationis industry or manufacturing tolerances. STEP3:Determine the thread pitch.To determine the thread pitch, use the Swagelok pitchgauges and check the thread against eachform untilyou find a match. If youprefer tonarrow down thechoices, use thefollowingprocedure:a.On the appropriate thread identification referencetable, locate the nominal thread diameter. Notethat it is common to have the thread diameterfor different threads listed multiple times.Turn to the Tapered Thread IdentificationReference Tables beginning on page 12.Figure 2.Measuring the Thread DiametersLast4th1stLast4th1st8IDENTIFICATIONb.For each case, read across the table to thepitch column to determine the possible threadpitches for your thread.c.Try the appropriate pitch gauge form for thethreads identified in Step b. above until you finda match. (See Figure 3.)STEP4:Determine the thread standard.Once you have determined the following abouta thread, you have all the information required toidentify it:IMale or femaleIStraight or taperedINominal male or female diameterIPitchNow, turn to the appropriate thread identificationreference table and identify the thread.STEP5:Identify the end connection.If the thread is tapered:a.Locate the end connections that have thetapered thread you identified. (Seepages 20through 23.)b.Study the cross-section drawings for these endconnections and determine which one matchesyour end connection.T1.5 mm perthread18 threadsper inchNo MatchMatchFigure 3.Determining the Thread Pitch

一. 螺纹的分类

1. 螺纹分内螺纹和外螺纹两种；

2. 按牙形分可分为：１）三角形螺纹 ２）梯形螺纹 ３）矩形螺纹 ４）锯齿形螺纹；

3. 按线数分单头螺纹和多头螺纹；

4. 按旋入方向分左旋螺纹和右旋螺纹两种, 右旋不标注，左旋加LH，如M24×1.5LH；

5. 按用途不同分有：米制普通螺纹、用螺纹密封的管螺纹、非螺纹密封的管螺纹、60°圆锥管螺纹、米制锥螺纹等

二. 米制普通螺纹

1. 米制普通螺纹用大写M表示，牙型角2α=60°（α表示牙型半角）；

2. 米制普通螺纹按螺距分粗牙普通螺纹和细牙普通螺纹两种；

2.1. 粗牙普通螺纹标记一般不标明螺距，如M20表示粗牙螺纹；细牙螺纹标记必须标明螺距，如M30×1.5表示细牙螺纹、其中螺距为1.5。

2.2. 普通螺纹用于机械零件之间的连接和紧固，一般螺纹连接多用粗牙螺纹，细牙螺纹比同一公称直径的粗牙螺纹强度略高，自锁性能较好。

3. 米制普通螺纹的标记：M20-6H、M20×1.5LH-6g-40,其中M 表示米制普通螺纹，20表示螺纹的公称直径为20mm，1.5表示螺距，LH表示左旋，6H、6g表示螺纹精度等级，大写精度等级代号表示内螺纹，小写精度等级代号表示外螺纹，40表示旋合长度；

三. 用螺纹密封的管螺纹（GB 7306与ISO7/1相同）

1. 用螺纹密封的管螺纹不加填料或密封质就能防止渗漏。用螺纹密封的管螺纹有圆柱内螺纹和圆锥外螺纹、圆锥内螺纹和圆锥外螺纹两种连接形式。压力在5×105Pa以下时，用前一种连接已足够紧密，后一种连接通常只在高温及高压下采用。

2. 用螺纹密封的管螺纹内螺纹有圆锥、圆柱两种形式。外螺纹只有圆锥一种形式。牙型如下：锥度1：16，牙形角55°，旧螺纹标准示例：ZG3/8；

3. 标记示例：

圆锥内螺纹 Rc 3/8

管螺纹与标准螺纹换算标准

尺寸代号 每英寸牙数 螺 距 螺纹 直 径

（in) n p 大径D、d 小径D1、d1

1/16 28 0.907 7.723 6.561

1/8 28 0.907 9.728 8.566

1/4 19 1.337 13.157 11.445

3/8 19 1.337 16.662 14.95

1/2 14 1.814 20.955 18.631

5/8 14 1.814 22.911 20.587

3/4 14 1.814 26.441 24.117

7/8 14 1.814 30.201 27.877

1 11 2.309 33.249 30.291

1-1/8 11 2.309 37.897 34.939

1-1/4 11 2.309 41.91 38.952

1-1/2 11 2.309 47.803 44.845

1-3/4 11 2.309 53.746 50.788

2 11 2.309 59.614 56.656

2-1/4 11 2.309 65.71 62.752

2-1/2 11 2.309 75.184 72.226

2-3/4 11 2.309 81.534 78.578

3 11 2.309 87.884 84.926 3-1/2 11 2.309 100.33 97.372

4 11 2.309 113.03 110.072

5 11 2.309 138.43 135.472

6 11 2.309 163.83 160.872

注：1in=25.4mm

1、用螺纹密封的管螺纹其标记及各种螺纹的特征代号规定如下：

Rc—圆锥内螺纹

Rp—与圆锥外螺纹配合的圆柱内螺纹

R—圆锥外螺纹

标准规定将螺纹尺寸代号写在特征代号之后，若螺纹为械旋应再加写左旋

代号LH，具体示例如下：

圆锥内螺纹：Rc1/2

左旋圆柱内螺纹：Rp1/2—LH

圆柱内螺纹与圆锥外螺纹的配合：Rp2/R2

中国螺纹标准

中国螺纹标准主要由国家标准制定，涵盖了各种类型和用途的螺纹。以下是一些常见的中国螺纹标准：

1.GB/T 1167： 这个标准规定了内螺纹和外螺纹的基本和一般要求。它包括了螺纹的设计、公差、尺寸和标记等方面的内容。

2.GB/T 5287： 这个标准规定了公制内螺纹和外螺纹的基本尺寸和公差。

3.GB/T 5796： 这个标准适用于螺纹公差和螺纹测量。

4.GB/T 18455： 这个标准规定了非金属软管用管螺纹尺寸。

5.GB/T 19201： 这个标准适用于建筑结构用的螺栓连接。

6.GB/T 3098.1： 这个标准规定了普通螺纹连接的螺栓和螺母。

7.GB/T 12616： 这个标准适用于机械连接的六角螺母。

8.GB/T 1229： 这个标准规定了紧固螺钉的名称、类型、尺寸和材料。

这些标准包括了不同类型螺纹的设计、尺寸、公差、材料、用途等方面的要求。螺纹标准在各种行业和应用中广泛使用，确保了螺纹连接的互换性和可靠性。