In mechanical parts or other market industries, in order to standardize the manufacturing quality of products, at the same time, taking into account the possibility of over-filling by manufacturers and the convenience of consumers' choice, the relevant departments have issued many standard documents for reference. For example, the standard of threaded joints cited by Xiaobian in the following paragraphs is a representative one, and friends who are interested in purchasing, or those who want to produce, design and sell in large quantities can refer to the actual situation for in-depth understanding.
1. threaded joint standard
1. English pipe thread (55)
includes: general sealed pipe thread (R), unsealed pipe thread (G), old English pipe thread (PT, PF) from Korea and Japan
2. American pipe thread (6)
includes: general sealing pipe thread (NPT, NPSC), dry sealing pipe thread (NPTF, NPSF, NPSI, PTF-SAE? SHORT), unsealed pipe threads (NPSM, NPSL, NPTR, NPSH, NH, NHR)
3. Metric pipe threads (6)
include: general sealed metric pipe threads (MC, MP) and unsealed metric pipe threads (M).
refer to the metric, American and English thread standard manual?
in China's old mechanical drawing standard, the thread code of 55 sealed conical pipe is ZG, and the thread code of 6 general sealed conical pipe is Z.
In China's new mechanical drawing standard, the thread of 55 sealed conical pipe is changed to cylindrical internal thread/conical external thread (RP/R1)[1]? , tapered internal thread/tapered external thread (RC/R2)[2]? ; The thread code of 6 general sealed conical pipe is NPT (according to American standard). See GB/T for details? 736-2。
both the old and new 55 unsealed cylindrical pipe threads are coded as g.
ii. marking of English pipe thread (55)
(1) marking of English sealed pipe thread (R)
The complete marking of English sealed pipe thread consists of thread feature code, thread size code and rotation code.
when the thread is left-handed, the rotation code "LH" should be added; The spin code of right-handed thread is omitted.
① cylindrical internal thread and conical external thread [1]
Thread feature code: RP? —— Represents the internal thread of a cylinder;
R1 refers to the conical external thread matched with the cylindrical internal thread;
when representing a thread pair, the thread feature code is RP/R1 (cylindrical internal thread/tapered external thread)
Example of marking:
Right-handed cylindrical internal thread with the size code of 3/4 is marked as RP? 3/4;
left-handed cylindrical internal thread with dimension code 3/4, marked as RP? 3/4? LH;
right-handed conical external thread with dimension code 3, marked R1? 3;
a thread pair consisting of right-handed cylindrical internal thread and conical external thread with size code 3, marked as RP/R1? 3
② Tapered external thread and tapered internal thread [1]
Thread feature code: RC-representing tapered internal thread;
R2—— indicates the conical external thread matched with the conical internal thread;
when representing a thread pair, the thread feature code is RC/R2 (tapered internal thread/tapered external thread)
Example of marking:
Right-handed tapered internal thread with the size code of 3/4 is marked as RC? 3/4;
left-handed conical internal thread with dimension code 3/4, marked as RC? 3/4? LH;
right-handed conical external thread with dimension code 3, marked R2? 3;
a thread pair consisting of right-handed conical internal thread and conical external thread with size code 3, marked as RC/R2? 3
⑵? 55 inch unsealed pipe thread (G)
The complete marking of inch unsealed pipe thread consists of thread feature code, thread size code, pitch diameter tolerance grade code and rotation direction code.
The characteristic code of English unsealed cylindrical thread is: G
For English unsealed cylindrical internal thread, the code of diameter tolerance grade is omitted; However, the middle diameter meter grade code of English unsealed cylindrical external thread is A and B respectively.
the rotation direction code of the left-handed thread is LH; The spin code of right-handed thread is omitted.
when representing the thread pair of English unsealed pipe thread, only the marking code of external thread is marked.
example:
right-handed, unsealed cylindrical internal thread with dimension code 2: G2
Grade A with dimension code 3, right-handed, unsealed cylindrical external thread: G3
Grade B with dimension code 4, left-handed and unsealed cylindrical external thread: G4? B-LH
Thread pair consisting of right-handed, unsealed cylindrical internal thread and A-level cylindrical external thread with dimension code number 2: G2A
Is it a pipe thread tap that processes the internal hole thread? There are dies for processing external threads.
if you want to ensure the proper use effect of threaded joints in the later period, it is necessary to start with the analysis with reference to the above-mentioned standards, otherwise, consumers will not be able to buy high-quality products, and manufacturing enterprises will not be able to guarantee qualified quality. Therefore, Xiao Bian believes that it is necessary for everyone to follow the appropriate normative text to understand. For example, British pipe thread, American pipe thread and metric pipe thread are completely different standards, and confusing friends need to distinguish them more.
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