A cutting tool fastener having a rotation axis (A) and configured to secure together, and establish a fluid path between, two cutting tool members , while also accommodating angular and pivotal displacement between the two, the fastener comprising: a head comprising a head peripheral surface having at least one head opening for emitting fluid; and a body extending from the head and comprising: a body peripheral surface ; a body opening for receiving fluid to be emitted via the head opening ; an internal fastener fluid channel extending at least partially along the rotation axis (A) and in fluid-communication with the head and body openings ; and top sealing means configured for providing fluid seal, the top sealing means being located at the head , axially above the head opening and away from the body ; characterised in that : the head peripheral surface comprises a spherical head abutment surface , at least a portion of which faces towards the body ; the spherical head abutment surface comprises a bottom spherical seal surface zone ; the head opening opens out to the spherical head abutment surface ; and the bottom spherical seal surface zone is axially located between the body and the head opening . a head comprising a head peripheral surface having at least one head opening for emitting fluid; and a body extending from the head and comprising: a body peripheral surface ; a body opening for receiving fluid to be emitted via the head opening ; an internal fastener fluid channel extending at least partially along the rotation axis (A) and in fluid-communication with the head and body openings ; and top sealing means configured for providing fluid seal, the top sealing means being located at the head , axially above the head opening and away from the body ; characterised in that : the head peripheral surface comprises a spherical head abutment surface , at least a portion of which faces towards the body ; the spherical head abutment surface comprises a bottom spherical seal surface zone ; the head opening opens out to the spherical head abutment surface ; and the bottom spherical seal surface zone is axially located between the body and the head opening . a body peripheral surface ; a body opening for receiving fluid to be emitted via the head opening ; an internal fastener fluid channel extending at least partially along the rotation axis (A) and in fluid-communication with the head and body openings ; and top sealing means configured for providing fluid seal, the top sealing means being located at the head , axially above the head opening and away from the body ; characterised in that : the head peripheral surface comprises a spherical head abutment surface , at least a portion of which faces towards the body ; the spherical head abutment surface comprises a bottom spherical seal surface zone ; the head opening opens out to the spherical head abutment surface ; and the bottom spherical seal surface zone is axially located between the body and the head opening . the head peripheral surface comprises a spherical head abutment surface , at least a portion of which faces towards the body ; the spherical head abutment surface comprises a bottom spherical seal surface zone ; the head opening opens out to the spherical head abutment surface ; and the bottom spherical seal surface zone is axially located between the body and the head opening . <EOS>