A replaceable cutting head , for rotary cutting operations, having a head longitudinal axis (A) around which the replaceable cutting head rotates in a direction of rotation (R), the head longitudinal axis (A) extending in a forward (D F ) to rearward direction (D R ), comprising: a forward portion forming a cutting portion and a rearward portion forming a mounting portion , wherein; the mounting portion comprises a male coupling member protruding rearwardly from a rearwardly facing head base surface , the head base surface extending transversely with respect to the head longitudinal axis (A), and defining a boundary between the cutting portion and the mounting portion , the male coupling member comprising: outwardly facing forward and rearward bearing portions and an external thread located therebetween wherein; the forward bearing portion comprises a conically shaped forward head abutment surface that tapers inwardly in a rearward direction (D R ) defining a forward head cone angle (α); and the rearward bearing portion comprises a conically shaped rearward head abutment surface that tapers inwardly in a rearward direction (D R ) defining a rearward head cone angle (β); characterised in that the forward and rearward head abutment surfaces are ground, and the forward and rearward head cone angles (α, β) are within ± 0.5° of each other. a forward portion forming a cutting portion and a rearward portion forming a mounting portion , wherein; the mounting portion comprises a male coupling member protruding rearwardly from a rearwardly facing head base surface , the head base surface extending transversely with respect to the head longitudinal axis (A), and defining a boundary between the cutting portion and the mounting portion , the male coupling member comprising: outwardly facing forward and rearward bearing portions and an external thread located therebetween wherein; the forward bearing portion comprises a conically shaped forward head abutment surface that tapers inwardly in a rearward direction (D R ) defining a forward head cone angle (α); and the rearward bearing portion comprises a conically shaped rearward head abutment surface that tapers inwardly in a rearward direction (D R ) defining a rearward head cone angle (β); characterised in that outwardly facing forward and rearward bearing portions and an external thread located therebetween wherein; the forward bearing portion comprises a conically shaped forward head abutment surface that tapers inwardly in a rearward direction (D R ) defining a forward head cone angle (α); and the rearward bearing portion comprises a conically shaped rearward head abutment surface that tapers inwardly in a rearward direction (D R ) defining a rearward head cone angle (β); characterised in that the forward bearing portion comprises a conically shaped forward head abutment surface that tapers inwardly in a rearward direction (D R ) defining a forward head cone angle (α); and the rearward bearing portion comprises a conically shaped rearward head abutment surface that tapers inwardly in a rearward direction (D R ) defining a rearward head cone angle (β); characterised in that the forward and rearward head abutment surfaces are ground, and the forward and rearward head cone angles (α, β) are within ± 0.5° of each other. <EOS>