Application of Overburden Drilling System (Symmetrix / Ring Bit):
The ring bit enlarges a pilot hole to casing size in one pass through loose or unstable overburden. It stays folded while drilling down; rotating and lowering the casing expands the bit to widen the hole, and reversing that motion folds it back in for retrieval once casing is set.
Features of Overburden Drilling System
– Casing stays in place through loose ground, preventing hole collapse behind the bit.
– Covers small (160–315mm) through extra-large (860–1010mm) casing ranges.
– Compatible with SD5, DHD350/360/380, QL80, and N-series hammer shanks.
– Suited to mining, pile installation, geotechnical investigation, and tunnelling work.
Size Range of Overburden Systems
| Class | Casing Range | Ring Bit OD |
| Small | 160–315mm | 214–373mm |
| Medium | 365–560mm (16″–24″ casing) | 425–630mm |
| Large | 600–810mm (26″–34″ casing) | 685–886mm |
| Extra-Large | 860–1010mm (36″–42″ casing) | 945–1100mm |
Note: Extend-Shrink Bit and Supermax Bit variants also available — confirm casing size and hammer shank before ordering.