Cross-over sub acts for conversion and connection of drill stem component in petroleum, natural gas and geology drilling work. It is used mainly for connecting of upper drill tools and lower drill tools during drilling operations.
Type a stand for same diameter: One crossover sub has one size (d)on o. D., code a.
Type b stands for reduce type: One crossover sub has two sizes (d1, d2) on o. D., code b.
Type c is left hand thread type: The connection thread is left hand type, code c.
The cross over sub in 4 types of main structure:
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