Device for drilling in and/or lining holes in earth

A device for drilling holes in earth, rock or similar bodies, comprising a casing which is designed to be lowered together with a drilling unit, wherein the drilling unit is mounted on a rotating drilling string which is centrally positioned within the casing and the drilling string being provided with a first abutment which on downward movement of the drilling string is pressed against a second abutment within the casing to press the casing downward, said drilling string being provided with a plurality of cutters which can either be pivoted between an active and a passive position by activating means, said activating means comprising a hollow activating member which is operated by drilling fluid passing through the drilling string, characterized in that the activating member further includes an annular piston which is received within a cylinder arranged at the lower end of the drilling string, said annular piston connected to a concave rod and an activating cam having a passage way communicating with a valve for controlling the drilling fluid supplied to the cutters, and the lower end of the activating member is arranged to operatively engage the drilling cutters to move them to and from the active and passive positions and said valve being arranged to open when the cutters are moved to the active position.