SIZE	INNER DIAMETER (mm)	OUTER DIAMETER (mm)
ATW / AGM	36.8	44.5
BTW / BGM	48.8	56.5

Raw materials: Tangshan Jinshi only choose the best steel tubes in the market to manufacture our rods and pipes. Spot check will be conducted after the steel tubes delivered to company. We will make sure the compositions and specifications match the inspection report form the suppliers. Heat treatment control: Heat treatment will greatly improve the material strength and increase the thread wear life of the rods and casings. We conduct either tru-wall or both ends heat treatment to the tube body. After heat treatment, strength, hardness, straightness and concentricity of the treated tubes will be tested in our lab. Thread opening process:  Accuracy of threads will determine the use effects and life time of drill rod and casings. CNC latches and form cutter are used in thread opening processing to minimize error made by anthropic factors. Additional thread treatment: Surface of the threads will be cleaned to remove burr adhered after threads are opened. Afterwards, the tread surface will be phosphated to improve surface conditions.