FIELD: threaded connection for percussion drilling on ledge rock.
SUBSTANCE: connection is made between drill rod and bushing, connected to drilling bit. Drill rod on one end has external thread, and on other end - first external surface of constant diameter, and also second external surface, positioned in axial direction between first external surface and thread. Bushing is made with internal thread and has internal end stop surface and second circular end surface. Between second end surface and internal thread, cylindrical internal surface is positioned. Second end surface of bushing is positioned in axial direction behind the end of external thread or behind a gap in thread. Internal diameter of bushing is equal to diameter of second external surface of drill rod and is less than diameter of first surface of rod. First imaginary cylinder, formed by continuation of internal surface of bushing, intersects with drill rod. Second imaginary cylinder, formed by continuation of external surface of bushing, passes outside the drill rod.
EFFECT: decreased generation of vortices during percussion drilling due to minimization of difference of dimensions between drill rod and drilling bit.
6 cl, 4 dwg
