T38 Thread Extension Drilling Rod for Drilling Rocks

For extension rod, there are two shapes, one is round type, another one is hexagonal type. All extension rod are threaded and made by hollow drill steels.
This hollow hole are usually named flushing hole, used for transmitting water or air during drilling. Two ends threads can be used for connecting couplings, shanks, couplings or bits. Typically two ends of extension rods are male, while sometime one end is male and another one is female, then we call it M/F rod. We need couplings to connect extension rods, while for M/F rods, because one end is female, so couplings are not necessary.
Specifications:

Male/Female (M/F) rod, speed rod
M/F drill steel is an alternative to couplings sleeves to include the female part of the threaded connection as an integral part of the drill steel. M/F drill steel provides more rigid connections and is easier to uncouple and handle. The service life also tends to be better than with separate couplings. The advantages of drilling with M/F steel include: Easy handling, quicker uncoupling, tighter connections, the potential to drill straighter holes, and longer service life.
For Extension Rod and M/F steel process, the below two different types of heat treatment are used to strengthen high speed and powerful percussive drill string components to maximize their performance and reliability. Longer steel larger in diameter, conventional extension steel, Hexagonal and round cross sections are available.
- Carburization is a process used to harden the entire rod surface both internally and externally to strengthen and extend the life of the rod.
- High Frequency Induction is a process where only the thread ends of the rod are hardened to lengthen thread life.