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  • 你对螺纹常识有多了解?
  • 本站编辑:杭州天程钢铁有限公司发布日期:2019-11-29 21:11 浏览次数:

一、螺纹种类

按牙型可分为三角形、梯形、矩形、锯齿形和圆弧螺纹;

按螺纹旋向可分为左旋和右旋;

按螺旋线条数可分为单线和多线;

按螺纹母体形状分为圆柱和圆锥等。

二、螺纹的要素

    螺纹包括五个要素:牙型、公称直径、线数、螺距(或导程)、旋向。

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1. 牙型

    在通过螺纹轴线的剖面区域上,螺纹的轮廓形状称为牙型。有三角形、梯形、锯齿形、圆弧和矩形等牙型。

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2. 直径

螺纹有大径(d、D)、中径(d2、D2)、小径(d1、D1),在表示螺纹时采用的是公称直径,公称直径是代表螺纹尺寸的直径。

    普通螺纹的公称直径就是大径。

外螺纹(左)              内螺纹(右)

3. 线数

    沿一条螺旋线形成的螺纹称为单线螺纹,沿轴向等距分布的两条或两条以上的螺旋线形成的螺纹称为多线螺纹。

单线螺纹(左)            双线螺纹(右)

4. 螺距和导程

    螺距(p)是相邻两牙在中径线上对应两点间的轴向距离。

    导程(ph)是同一条螺旋线上的相邻两牙在中径线上对应两点间的轴向距离。

    单线螺纹时,导程=螺距;多线螺纹时,导程=螺距×线数。

5. 旋向

    顺时针旋转时旋入的螺纹称为右旋螺纹;

    逆时针旋转时旋入的螺纹称为左旋螺纹。

左旋螺纹                右旋螺纹

三、螺纹的标记

(1)普通螺纹

    普通螺纹用得最广泛,螺纹紧固件( 螺栓、螺柱、螺钉、螺母等零件)上的螺纹一般均为普通螺纹。

普通螺纹分粗牙普通螺纹和细牙普通螺纹。细牙普通螺纹多用于精密零件和薄壁零件上。

    在螺纹的标记中,细牙普通螺纹的螺距必须注出,而粗牙普通螺纹的螺距一般不标注。

    普通螺纹的标记由五部分组成:

1) 特征代号

    M     (表示普通螺纹)

2)尺寸代号

    尺寸代号:公称直径×螺距(多线螺纹的导程和螺距均要注出,单线粗牙普通螺纹螺距不标注)。

    “M10”表示公称直径为10 mm、螺距1.5 mm的单线粗牙普通螺纹。

    “M10×1”表示公称直径为10mm、螺距为1 mm的单线细牙普通螺纹。

2)普通螺纹的公差带代号

    由公差等级(数字)和基本偏差(外螺纹用小写字母、内螺纹用大写字母表示)所组成,例如5g6g、6g、6H、7H。

    当螺纹中径公差带与顶径公差带代号不同时,需分别注出,如:M10-5g 6g

    当中径与顶径公差带代号相同时,只注一个代号,如:M10×1-7H

    公差带代号为 6g 或 6H(公称直径≥ 1.6mm)时不标注。

3)普通螺纹的旋合长度

    有长、中、短三种,分别用代号L、N、S表示。

    M10-5g6g-S 为短旋合长度的螺纹

    M10-7H-L为长旋合长度的螺纹

    当螺纹为中等旋合长度时,代号N不标注。

    当特殊需要时,可注明旋合长度的数值。

    M20×2-5g6g-40

4)旋向代号

    左旋时标注LH,右旋时不标注。

    M10-7H-L-LH为左旋螺纹

    M10-7H-L为右旋螺纹

(2)管螺纹

    管螺纹一般用于管路(水管、油管、煤气管等)的连接中。管螺纹的标记用指引的方法标注,指引线指到螺纹的大径上。

管螺纹的标记:

    由螺纹特征代号、尺寸代号和旋向组成。尺寸代号不是螺纹大径的大小,而是管子的通径(英制)大小。标记中未注写旋向的均为右旋。

Type of thread

According to the tooth type can be divided into triangle, trapezoid, rectangle, serrated and arc thread;

According to the direction of the thread can be divided into left and right rotation;

According to the number of spiral lines can be divided into single-line and multi-line;

It can be divided into cylinder and cone according to the shape of thread matrix.

Ii. Elements of thread

Threads consist of five elements: tooth type, nominal diameter, number of threads, pitch (or lead), and direction of rotation.

1. The tooth type

In the section area passing through the thread axis, the profile shape of the thread is called the tooth type. There are triangle, trapezoid, serrated, circular and rectangular teeth.

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Diameter of 2.

Threads have large diameters (d, d), medium diameters (d2, d2), and small diameters (d1, d1). The nominal diameter is the diameter of the size of the thread.

The nominal diameter of common thread is the large diameter.

Male (left) female (right)

3. The line number

Threads formed along a helix are called single-thread threads, and threads formed along two or more helix threads evenly distributed along the axis are called multi-thread threads.

Single thread (left) double thread (right)

4. Pitch and lead

Pitch (p) is the axial distance between two adjacent teeth on the middiameter line.

Lead (ph) is the axial distance between two adjacent teeth on the same helix and two corresponding points on the middiameter line.

For single thread, lead = pitch; For multi-thread threads, lead = pitch × number of threads.

5. Handedness

The thread that is screwed in when clockwise is called the right thread;

The thread that is screwed in when counterclockwise is called the left-hand thread.

Left hand thread right hand thread

Marking of threads

(1) ordinary thread

Common thread is the most widely used, screw fasteners (bolts, studs, screws, nuts and other parts) are generally common thread threads.

Common thread can be divided into coarse thread and fine thread. Fine tooth common thread is used in precision parts and thin - walled parts.

In the marking of threads, the pitch of fine tooth common thread must be injected, while that of coarse tooth common thread is generally not marked.

The marking of ordinary threads consists of five parts:

1) feature code

M (for common thread)

2) size code

Size code: nominal diameter × pitch (lead and pitch of multi-thread threads should be noted, common thread pitch of single-thread coarse teeth is not marked).

"M10" represents the single-thread coarse tooth common thread with nominal diameter of 10 mm and pitch of 1.5 mm.

"M10×1" represents the single-thread fine tooth common thread with nominal diameter of 10mm and pitch of 1mm.

2) tolerance zone code for common thread

Made up of tolerance grade (Numbers) and base deviation (outer thread in lowercase letters, inner thread in uppercase letters), e.g. 5g6g, 6g, 6H, 7H.

If the middle diameter tolerance zone and the top diameter tolerance zone have different codes, please note them separately, such as m10-5g 6g

The middle diameter and the top diameter tolerance zone code are the same, only a code, such as: M10× 1-7h

If the tolerance zone code is 6g or 6H(nominal diameter ≥ 1.6mm), it will not be marked.

3) the screwing length of ordinary threads

There are long, medium and short, respectively with the code L, N, S.

M10-5g6g-s is a thread of short screwing length

M10-7h-l are threads of long screwing length

When the thread is of medium length, code N is not marked.

For special needs, the value of the rotational length may be indicated.

M20 x 2-5 g6g - 40

4) rotation code

LH is marked on the left, but not on the right.

M10-7h-l-lh is a left-hand thread

M10-7h-l is a right hand thread

(2) pipe thread

Pipe threads are generally used in connection with pipes (water pipes, tubing, gas pipes, etc.). The marking of pipe threads shall be indicated in the manner of a guide line to the large diameter of the thread.

Marking of pipe threads:

It is composed of thread characteristic code, dimension code and rotation direction. The size code is not the size of the thread diameter, but the size of the pipe diameter (inch). The ones not marked with rotation are all right-handed.