NPT, national pipe threads, and FPT, female pipe threads, are terms used regarding U.S. pipe standards for tapered threads. NPT are common threads used for general purposes, while FPT are a type of NPT.
Purpose
NPTs and FPTs are used to join pipes and fittings for all types of general purposes. This includes things such as joining low pressure air or liquid needs. They are also used for many mechanical applications.
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Types
NPTs are divided into categories. Two common types are MPTs, male pipe threads, and FPTs. These types represent joining pipes in different ways. Male and female pipe threads are needed to join pipes together.
Uses
Threaded pipes are used for sealing pipes together. They provide effective seals when liquids, gases, steam and hydraulic fluids are transported.
Size
All NPTs have tapered threads at a rate of 1/16. They have a 60 degree thread angle.