What is the specified size for threading a 1-inch iron pipe in gas piping installation?

In gas piping installations, the specific size for threading a 1-inch iron pipe is typically 7/8 inch. This sizing is related to how the pipe is designed to connect with fittings and components. The outside diameter of a nominal 1-inch iron pipe is larger than the actual size referenced by the nominal designation, and the threading size is based on the diameter of the internal threads, which is what connects with other fittings securely.

Choosing 7/8 inch for threading allows for an appropriate fit that ensures safety and compliance with gas piping standards. Other sizes listed do not correspond to the standard practices and would result in improper connections, compromising the integrity and functionality of the gas piping system.