1. Size: 3-1/8"  -  9 1/2"

2. Products description
Our drill collar 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 by Our, own unique Power Frequency Induction Heating Treatment machine.
Our manufactures not only slick Drill Collars, but also spiral Drill Collars with Slip, Elevator recesses and hardbanding.
Drill collars are available in lengths from 10 to 32 feet and outside diameter from 3-1/8" to 9-1/2".
No-magnetic drill collar are made from chrome manganese low carbon austenitic alloy, which has following characteristic.
The chemical composition should be controlled strictly during the refining and forging process.
With excellent lower Magnetic permeability, high strength of mechanical properties and outstanding resistant to stress corrosion cracking and no tendency to galling.

3. Usage
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.