How many threads per inch are cut on a 1-1/2 inch black steel pipe?

The number of threads per inch (TPI) for a 1-1/2 inch black steel pipe follows standard pipe threading specifications. According to the American National Standards Institute (ANSI) and the National Pipe Thread (NPT) standards, a nominal pipe size of 1-1/2 inches typically has a standard threading of 11.5 threads per inch.

This specification is significant because it ensures that fittings and connections are compatible and can create a proper seal when the pipe is joined with another fitting or pipe segment. Although there are variations in thread counts for different sizes of pipe, the 1-1/2 inch size standardizes at 11.5 TPI to maintain consistency across plumbing systems.

The other choices do not reflect the standard TPI for this nominal size, which is critical for ensuring the correct assembly and sealing of pipes in plumbing systems. It's important for those in the mechanical and plumbing fields to be familiar with these standards to ensure the proper functioning of the systems they work on.