What is the meaning API thread and IF thread and REG thread of drill rod?

1. API thread
2. IF thread
3. REG thread

​API thread
It is one of the most commonly used types of drill bit threads, suitable for most situations. Its full name is American Petroleum Institute thread, also known as circular mortise and tenon thread. There are three types of API threads: regular threads (API REG), internal threads (API IF), and external threads (API NC and API FH), with the commonly used being API REG.
The characteristics of API threads are deep thread profile, circular tenon, compact structure, and suitable for situations that require high load-bearing capacity. In drilling operations, API threads are commonly used to connect drill rods and drill bits, as well as between drill rods and drill pipes.

IF thread
The full name of IF thread is Internal Flush thread, also known as internal sealing thread. The characteristic of IF threads is that the thread profile is shallow, the tenon is hexagonal, and the structure is relatively simple.
IF threads are suitable for situations that require high corrosion resistance and strong sealing, such as water wells, oil wells, etc. The connection method is to connect the drill rod and drill bit through an internal sealing gasket.

REG thread
The full name of REG thread is Regular thread, also known as regular thread or regular thread. The characteristic of REG threads is the deep thread profile, which is the same as the API REG thread interface, but the tenon is hexagonal and the structure is relatively simple.
The main applications of REG threads are in areas where standard threads are not highly required, such as geological surveys, engineering exploration, and water source drilling. The connection method between drill pipe and drill bit is the same as API thread.