Drill collars are manufactured from AISI 4145H or 36CrNiMo4 modified steel, and are supplied in the" as rolled" surface finish condition. Alternative surface finishes can be provided.

Trepanning and Heat treatment:
Drill collars are trepanned and drifted to API Spec 7. Full-length heat-treatment processes ensure that mechanical properties meet or exceed API Spec 7 requirements. A hardness range of 285-341, Brinell Hardness and Charpy V notch minimum impact strength of 40 ft-lb at 70OF are guaranteed one inch below the surface.

Connections NC23 NC26and NC31 (2 3/8 IF and 2 7/8 IF) have a sufficient steel thickness for machining stress-relief grooves.

Drill collar material and process traceability are maintained from receipt of mill certified raw material to completion of all the manufacturing. Serial numbers are die stamped on bar bodies.

Rigid Inspection Procedures:
We inspect all our drill collars to comply with API standards . These inspections include visual dimensional checks as well as ultrasonic inspections over the entire body of the drill collar.

Cold Rolling:
Drill collar thread roots, as well as elevator recess upper radii, are cold-rolled. Cold rolling creates a compressive recess upper radii stress condition that increases fatigue life by minimizing crack initiation.

Phosphate-coated or copper plating:
All connections are phosphate-coated or copper plating to improve resistance to galling.

Slip groove, elevator groove and size: （API RP 7G）
Our company offers optional slip and elevator recesses to improve handling efficiency and safety. The upper radius of the elevator recess is cold can be used together or separately. Unless otherwise specified, slip and elevator recesses are machined in compliance with API RP 7G guidelines.

Thread protectors:
We offer steel and cast steel and plastic steel thread protectors for its drill stem products.