OD (Overburden Drilling) is a system for top hammer drilling using an inner drill string, usually a T45 rod with rock bit on it, and an outer casing with a ring bit (OD casing). You can choose between, first drilling the casing and then drill through it with the inner drill string, or you drill down the casing together with the inner drill string. The benefit of OD is that it is designed to enable pulling the casing up so it can be reused. The OD system we sell at Geomek is made by KLEMM.
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