Cylinder joint thread reference, what are the specifications of the cylinder joint thread?

1. Classification of threads
1. Threads are divided into two types: internal threads and external threads;
2. According to the tooth shape, it can be divided into: 1) Triangular thread 2) Trapezoidal thread 3) Rectangular thread 4) Zigzag thread;
3. According to the number of threads, it is divided into single-start thread and multi-start thread;
4. According to the screwing direction, there are two types: left-hand thread and right-hand thread. Right-hand thread is not marked, left-hand thread is added with LH, such as M24×1.5LH;

5. According to different uses, they are divided into: metric ordinary threads, thread-sealed pipe threads, non-thread-sealed pipe threads, 60° conical pipe threads, metric tapered threads, etc.





Cylinder joint thread reference, what are the specifications of the cylinder joint thread?


2. Metric ordinary thread
1. Metric ordinary thread is represented by a capital M, and the tooth profile angle 2α=60° (α represents the tooth profile half angle);
2. Metric ordinary threads are divided into two types according to the pitch: coarse thread ordinary thread and fine thread ordinary thread;
2.1. Coarse ordinary thread markings generally do not indicate the pitch, such as M20 indicating coarse thread;fine thread markings must indicate the pitch, such as M30×1.5 indicating fine thread, in which the pitch is 1.5.
2.2. Ordinary threads are used for connection and fastening between mechanical parts. Generally, coarse threads are used for threaded connections. Fine threads have slightly higher strength and better self-locking performance than coarse threads of the same nominal diameter.
3. Markings of metric ordinary threads: M20-6H, M20×1.5LH-6g-40, where M represents metric ordinary threads, 20 represents the nominal diameter of the thread is 20mm, 1.5 represents the pitch, LH represents left-hand, 6H and 6g represent threads Precision grade, the uppercase precision grade code indicates the internal thread, the lowercase precision grade code indicates the external thread, 40 indicates the screwing length;
3.1. The pitch of commonly used metric ordinary coarse threads is as follows (thread bottom hole diameter: carbon steel φ = nominal diameter - P;cast iron φ = nominal diameter - 1.05~1.1P;the diameter of the polished rod for processing external threads is φ = nominal diameter - 0.13 P)：
Table 1 Diameter/pitch of commonly used metric ordinary coarse threads





3.2. The diameter of the bottom hole for ordinary metric internal threads can be approximated by the following formula: d=D-1.0825P, where D is the nominal diameter and P is the pitch.





3. Pipe threads sealed with threads (GB 7306 is the same as ISO7/1)
1. Pipe threads sealed with threads can prevent leakage without adding fillers or sealants. Pipe threads sealed with threads have two connection forms: cylindrical internal threads and conical external threads, conical internal threads and conical external threads. When the pressure is below 5×105Pa, the former connection is tight enough, while the latter connection is usually only used under high temperature and high pressure.
2. The internal threads of pipe threads sealed with threads come in two forms: conical and cylindrical. External threads are only available in conical form. The tooth profile is as follows: taper 1:16, profile angle 55°, old thread standard example: ZG3/8;
3. Marking example:
Conical internal thread Rc 3/8
Cylindrical internal thread Rp3/8
Tapered external thread R3/8
When the thread is left-hand thread Rc 3/8-LH (LH means left-hand thread)
Basic dimensions of commonly used threads (marked: Rc 3/8, Rp3/8, R3/8):
Table 2





4. The marking method specified in GB 7306 is the same as that specified in ISO7/1. Before ISO 7/1 was unified, the marking methods in various countries were as follows:
table 3
Standard number Thread type Tapered internal thread Cylindrical internal thread Tapered external thread
ISO ISO7/1-1982 Rc1/2 Rp1/2 R1/2
British BS 21-1973 Rc1/2″ Rp1/2″ R1/2″
France NF E03-004 —— G1/2″J G1/2″
Germany DIN 2999 —— Rp1/2-DIN299 R1/2DIN2999
Japan JIS 130203 PT1/2″ PS1/2″ PT1/2″
Soviet Union ГOCT 6211 KTPYБ1/2″ —— KTPYБ