A turning tool holder includes a tool body, a cutting tool insert, and a shim. A coolant conduit system extends through the turning tool holder, a first portion of the coolant conduit system extending through the tool body and an end portion of the coolant conduit system extending through the shim. The end portion of the coolant conduit system includes a through hole extending from a first surface to an opposite second surface of the shim. The end portion has a coolant outlet opening at the second surface, the coolant outlet opening being formed by the shim alone. A jet of coolant from the coolant outlet opening may be directed towards a space expected to have a cutting zone of a workpiece. Further a cutting tool insert arranged to be used in a turning tool holder is disclosed.

A cutting insert has a top surface, a bottom surface, and an outer peripheral surface. A ridgeline between the top surface and the outer peripheral surface includes a first cutting edge. A protrusion is provided on the top surface. In a first cross section, a distance between the first cutting edge and the protrusion in a direction perpendicular to the bottom surface is defined as a first distance. In a second cross section, a distance between the first cutting edge and the protrusion in a direction perpendicular to the bottom surface is defined as a third distance. The third distance is longer than the first distance. A ratio of a height of the protrusion to a width of the protrusion in the second cross section is smaller than a ratio of a height of the protrusion to a width of the protrusion in the first cross section.