Drill for percussion drilling machines

Claim 1

A drill for use in a drilling machine for working on rocks and concrete and especially for use with percussion drilling machines and rotary drill hammers, comprising an axially elongated drill shank formed of a hardened material and having a first end arranged to contact within the adapter of the drilling machine, said adapter being provided with an inner thread, said second end having an axially extending outer surface, wherein the improvement comprises that a unitary receiving part is disposed in mechanical interlocking surface contact connection with and extends at least partly about and laterally encloses the axially extending outer surface of the second end of said drill shank and is formed entirely of a plastic material which has a lower hardness than that of the material forming said shank, said receiving part having an axially extending radial inner surface in full surface contact with the axially extending outer surface of said second end of said drilling shank, said surfaces being formed for mechanical interlocking connection, said receiving part having further and axially extending radial outer surface provided with a thread for engagement with said inner thread of the adapter of the drilling machine so that because of its lower hardness said receiving part is deformable under the action of the torque transmitted to it by the adapter, said receiving part having a leading end closer to the first end of said shank and a trailing end spaced axially from the leading end, and the second end of said drill shank extending through said receiving part at least to the trailing end of said receiving part so that axial blows are transmitted directly to the second end of said drill shank.