（英式）管用ねじ　下穴径とタップの工具径は？　rｃ　pt | オーエスジー

What is the pilot hole diameter and the tool diameter of the tap? Rc PT G PF

Please refer to the following link for the pilot hole diameter of the pipe screw.

You can check the pilot hole diameter and tap outer diameter of the following screws.
Tapered screw for pipes (English type) PT Rc
Parallel screw for pipes G PF

The name of the pipe screw is expressed in inches, but it is another number that cannot be calculated by. The outer diameter of the screw is also larger than that calculated from inches. This is stipulated in the standard. Please calculate the machining conditions of the tap by referring to the outer diameter of the screw in the table for the tool diameter.