A replaceable cutting head includes a forward cutting portion and a rearward mounting portion. The mounting portion includes a male coupling member that protrudes rearwardly from a base surface. The male coupling member includes three circumferentially spaced apart head fixation members, where each head fixation member has a head peripheral surface that spirals inwardly in a direction against the direction of rotation and diverges. A tool holder includes a female coupling member extends rearwardly from a holder forward surface. The female coupling member includes three circumferentially spaced apart holder fixation members, where each holder fixation member has a holder peripheral surface that diverges rearwardly. When a cutting tool, which includes said cutting head and tool holder, is in a locked position, the male coupling member of the replaceable cutting head is removably retained within the female coupling member of the tool holder by means of a self-lock mechanism.