Drilling tool with a two part input unit

A drilling tool arranged to be inserted into a drilling machine for use in boring holes and the like where rotational movement developed in the drilling machine is transferred to the drilling tool, said drilling tool comprising a drilling member and an input unit, said drilling member comprises an axially elongated shank having a forward end shaped to effect boring action and a rearward end, said input unit being formed at least in part of material having a different and lower thermal conductivity than the material forming said drilling member and laterally enclosing at least an axially extending portion of said rearward end, said input unit having an outer surface spaced radially outwardly from and extending circumferentially about the rearward end of said shank and arranged to fit into and to transmit the rotational movement of the drilling machine to said drilling member, said input unit being formed of at least a first material and a second material with said first material having a higher thermal conductivity than said second material and forming at least part of the outer surface of said input unit, said second material having the different and lower thermal conductivity than the material forming said drilling member, wherein the improvement comprises a heat conducting bridge extending between the outer surface of said input unit and said shank, said heat conducting bridge being formed of said first material, said heat conducting bridge being capable of transmitting heat radially outwardly from said shank of said drilling member and said second material being of a softer material than the material of said drilling member and being in contact with said heat conducting bridge and filling said input unit between the outer surface thereof and said shank so that the combination of said first and second materials affords sufficient strength to said input part to transmit the rotational movement of the drilling machine to said shank.