Method for drilling and drilling apparatus to enable reverse circulation

Abstract

The invention relates to a method for drilling, being carried out by a drilling apparatus, having a drilling device () that comprises a casing part () and a drilling unit (), in the drilling head (I) of which there are first drilling means () for drilling a center hole and second drilling means () for reaming of the center hole for the casing part () as well as flushing flow arrangement () for flushing of waste, being generated. At least during the drilling situation, the first drilling means () are coupled by a power transmitting and, in order to enable removal of the same from the hole, removable arrangement, such as a bayonet coupling or like, with the second drilling means (). A feed flow () of flushing medium, being carried out centrally, is being transferred by internal drillings (X) inside a first frame part (), belonging to the first drilling means (), to its outer periphery and a return flow () of flushing medium, in order to accomplish a so called reverse circulation of flushing medium, from the drilling surface (pp) of the first frame part () through internal drillings (X) therein into a space (z) between the first frame part () and the casing part (). The invention relates also to a drilling apparatus for exploitation of the method described above.