Let’s talk about the differences between G1/2'' and NPT1/2''

G 1/2\" is a cylindrical, unsealed pipe thread with a nominal size of 1/2\", a thread angle of 55°; it belongs to the British standard for pipe threads, and both the internal and external threads are denoted by G. NPT 1/2\" is a conical, sealed pipe thread with a nominal size of 1/2\", a thread angle of 60°; it belongs to the American standard for pipe threads. For more details, see Section 1: NPT threads – NPT refers to the American standard conical pipe threads used for general purposes. Here, N denotes the National (American) standard in the United States; P refers to PIPE, which are pipes; T stands for TAPER, with a thread angle of 60°. This type of pipe thread is commonly used in North America, or is frequently seen in ANSI standards. **The standard can be found in GB/T12716-1991. I must note that NPT threads should be used when following ANSI specifications! II. PT thread: The PT thread is a British standard tapered thread with a thread angle of 55°, and it is most commonly used for sealing purposes. It is mostly used in Europe and the Commonwealth; actually, Taiwan and Japan also follow imperial standards under the JIS regulations, and China as well uses imperial thread standards. It belongs to the Whitworth thread family. **The standard can be found in GB/T7306-2000. British pipe threads are fine-threaded, as coarse-threaded threads have a greater thread depth, which significantly reduces the strength of the pipe whose outer diameter such threads are cut into. Furthermore, in the actual installation of pipelines with small diameters, NIPPLES are often used. The reason for this is that the walls of commercially available NIPPLES are relatively thick, which ensures the strength of the threaded sections; at the same time, the main pipeline does not require thick walls, thereby helping to save costs. PF threads are effective parallel threads. I must keep in mind that PT teeth and the like must be used when following the JIS standards! III. Others: G refers to unthreaded sealing pipe threads with a 55-degree angle; it belongs to the Whitworth thread family. The designation G denotes cylindrical threads. **For standards, refer to GB/T7307-2001. G is an umbrella term for pipe threads; the distinctions between 55-degree and 60-degree threads are based on functional considerations, and they are commonly known as round pipe threads. That is, the thread is formed by machining a cylindrical surface. ZG is commonly known as pipe thread, meaning that the threads are formed by a conical surface; most water pipe fittings use this type of thread. The old national standard denotes it as Rc. Metric threads are specified by their pitch, while imperial and American threads are specified by the number of threads per inch – this is their main difference. Metric threads have an equilateral tooth profile at 60 degrees, imperial threads have an isosceles tooth profile at 55 degrees, and American threads also have a 60-degree tooth profile. Metric threads use metric units, while imperial and American threads use imperial units. Pipe threads are primarily used for connecting pipes; their internal and external threads fit tightly together, and there are two types: straight pipes and tapered pipes. The nominal diameter refers to the diameter of the pipe being connected; obviously, the major diameter of the thread is larger than the nominal diameter. 1/4, 1/2, 1/8 are the nominal diameters of imperial threads, measured in inches.

Correct, one more thing to add. Unsealed pipe thread = BSPP thread

G 1/2\" is a cylindrical, non-sealing pipe thread with a nominal size of 1/2\", a thread angle of 55°; it belongs to British pipe threads, and both the internal and external threads are denoted by G. 4 Z- j8 i5 ~8 [5 @1 u NPT 1/2\" is a conical, sealing pipe thread with a nominal size of 1/2\", a thread angle of 60°; it belongs to American pipe threads

This post was last edited by Shuguang Bellows on 2014-5-28 at 17:00. G refers to a 55-degree unsealed pipe thread, which belongs to the Whitworth thread family. The designation G indicates a cylindrical thread. **The relevant standard can be found in GB/T7307-2001; NPT is an abbreviation for National (American) Pipe Thread, representing a 60-degree tapered sealed pipe thread under American standards, used in North America.** The relevant standard can be found in GB/T12716-2011； In terms of the thread angle: British threads have a thread angle of 55 degrees, while American threads have 60 degrees. Pipe threads are primarily used for connecting pipes; their internal and external threads fit tightly together, and there are two types: straight pipes and tapered pipes ； The NPT is used for machinery or low-pressure gases and liquids, and sealants are required to ensure a tight seal.

The thread types are different, as those upstairs have explained very clearly.

It’s that simple. There are various sealing types: threaded sealing, face sealing (including ED sealing and O-ring sealing), and metal hard sealing. NPT refers to threaded sealing; however, due to manufacturing errors in China, tape or glue is sometimes used to ensure reliable sealing. G represents face sealing, which can be achieved through ED sealing or O-ring sealing. You can think of G as the metric equivalent of M threads, with only slight differences in size. Depending on the customer’s requirements, you choose the appropriate type of thread. When it comes to pressure gauges, G and NPT are commonly used (both are available abroad, while in China NPT is more common). The more experience you gain, the easier it will be to classify different threads based on their sealing type

Is NPT a tapered pipe thread of the G thread type, a parallel thread? I’m not sure