The drill collar is used between the drill pipe and the bit in the drill stem. It is used to put weight on the bit so that the bit can drill. 
SFMC drill collars are made of AISI 4145H or 4145H modified alloy steel. Its bores are trepanned from one direction with no mismatch. All drill collars are Q&T overall length.
SFMC manufactures not only slick Drill Collars, but also spiral Drill Collars with slip, elevator recesses and hardbanding upon client’s option. SFMC drill collars are available in lengths from 10 to 45 feet and outside diameter from 3-1/8" to 11".
SFMC also make high torque threads such as Double shoulder NC31,NC38,NC46,NC50 and 5-1/2”FH specified by clients