What is the effective number of threads of a 1/4" diameter screwed steel pipe?

The effective number of threads for a 1/4" diameter screwed steel pipe is determined by the standardized threads for pipes, also known as National Pipe Thread (NPT). This standard specifies various pipe sizes and their corresponding threads per inch.

For a 1/4" pipe, the standard calls for a specific number of threads: it is defined to have 18 threads per inch. This measurement is essential in ensuring proper fittings and sealing capabilities when connecting different sections of pipe.

Thus, the effective number of threads for a 1/4" diameter screwed steel pipe is indeed 18. Understanding standardized measurements in piping is crucial for both installation and maintenance, ensuring compatibility across various systems and components.