1. Structure of concentric casing system
Casing shoe:  Used to connect the casing tube.
Ring bit:  Used to connect the pilot bit and casing shoe.
Pilot bit:  The major structure of concentric casing system,with buttons and flushing grooves, etc.

2. Operation procedure

1. Concentric system drilling through overburden
2. Reverse rotation of the hammer and pull out the pilot bit.
3. Replace the pilot bit to normal bit to continue drilling
 

3. Scope of application:
Applicable to overburden with complex dry geological conditions, such as pebbles, cracks, dry rocks, boulders, construction backfill waste, etc. Drilling holes at any angle with high straightness
The maximum hole depth can reach 150 meters

4. Structural advantages:
Straightness: Under different geological structures, the straightness of hole formation can be guaranteed
Adaptability: In complex geological structures, such as pebbles and construction waste, the drilling efficiency can be guaranteed.
Less Torque: Less torque compared to eccentric drilling system.
Easy to Unlock and Relock: Easy to relock after unlocking.
Drilling at any angle: the concentric tubular drilling tool can drill in vertical, horizontal and inclined states.
Environmental protection: Compared with eccentric drilling tools, it is more suitable for construction in urban areas because of its stable drilling, low vibration and low noise.