Drill collars

According to API Spec.7 and SY/T5144, drill collar is made of AISI 4145 modified chromium- molybdenum alloy steel. All threads are phosphated, copperized or cold rolled , and they are machined with CNC Lathes –Double –shoulderd, including some special threads. We can supply drill collars in length from 10 to 45 feet and outside diameter from 3-1/8" to 11".The maximum outer diameter of drill collars can amount to 14”.