Q: For PS and PF screw types, is it possible to share thread‑machining tools and gauges? 

A: Both are parallel pipe threads, but their tolerance settings differ. 

Machining tools can be shared, but gauges cannot. You must use the gauge specified in the drawing.

Division	External thread	Internal thread	Combination
For tight coupling Tapered screw for pipes Example: Prevent water and gas from leaking	R(PT) Taper	Rc(PT) Taper
		Rp(PS) parallel
Mechanical coupling Pipe parallel screw Examples: Protection tubes for wiring cables, etc.	G(PF) parallel	G(PF) parallel

The pitch diameter of the internal thread differs between PF and PS. A PS tap cannot be used for a PF internal thread, and a PF tap cannot be used for a PS internal thread.

PS has a negative tolerance from the standard dimension, emphasizing tightness, while PF has a positive tolerance, emphasizing fit. If a tap for mechanical coupling (G/PF) is used to machine a thread intended for tight coupling (Rp/PS), sufficient sealing resistance cannot be achieved, creating a risk of leakage.

When selecting machining tools and gauges, be sure to choose the thread type specified in the drawing.