A type,B type &C type drill collar.
Type A(Cylindrical):Be made of Alloy Steel and the craoss sections of the inside and outside pipe are both round.
Type B(Spiral):Be made of alloy steel and the outside pipe has spiral grooves.
Type C(Non-magnetic):Be made of stainless alloy steel with rather low magnetic permeability and the cross sections of the inside and outside pipe are both round.
A type,B type &C type drill collar.
Type A(Cylindrical):Be made of Alloy Steel and the craoss sections of the inside and outside pipe are both round.
Type B(Spiral):Be made of alloy steel and the outside pipe has spiral grooves.
Type C(Non-magnetic):Be made of stainless alloy steel with rather low magnetic permeability and the cross sections of the inside and outside pipe are both round.
A type,B type &C type drill collar.
Type A(Cylindrical):Be made of Alloy Steel and the craoss sections of the inside and outside pipe are both round.
Type B(Spiral):Be made of alloy steel and the outside pipe has spiral grooves.
Type C(Non-magnetic):Be made of stainless alloy steel with rather low magnetic permeability and the cross sections of the inside and outside pipe are both round.
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