String Cross-Over Sub

String Cross-Over Sub It is a component(sub) used for joint between both drill stem

String Cross-Over Sub

Divided into seven Types by Application
sort	name	top connection	bottom connection	type
1	Kelley saver sub	kelly	drill pipe	A or B
2	Tool joint	drill pipe	drill pipe	A or B
3	Crossover sub	drill pipe	drill collar	A or B
4	Dril colar sub	drill collar	drill collar	A or B
5	Bit sub	drill collar	bit	A or B
6	Swivel sub	swivel bottom sub	kelly	C
7	Junk sub	kelly	drill pipe	C
		drill pipe	fishing tool	C

String Cross-Over Sub