Assembly of a reaming tool, that includes a clamping part, a reaming bit and a dismantling key. The clamping part is provided with a driving pin and with a hollow seating central protrusion. The reaming bit is provided with a central through opening for depositing on the seating central protrusion of the clamping part. On a cutting part a frontal surface is provided with a central axis on which a through conical opening is provided. On the clamping part of the reaming tool a frontal abutting surface is provided. In the central axis of the clamping part, there is a tubular conical protrusion, whose apex angle is smaller than the apex angle of the through conical opening. On the frontal abutting surface of the clamping part at least one recess is provided corresponding in shape to the functional part of the dismantling key.