Cutting tool with detachable insert, head member and tool body of the same

A head member for a cutting tool with detachable insert comprising a head member body formed with an insert attachment seat to which a cutting insert having cutting blades is detachably attached, and constituting the cutting tool by being mounted to a tip portion of a holder,

• wherein the insert attachment seat is formed by a pressing surface of one jaw portion and a pedestal surface of the other jaw portion in a pair of jaw portions formed in the head member body so as to be opened towards the tip side and extend towards a rear end side of the head member body,
• wherein from a rear end of the insert attachment seat, a slit is provided so as to further extend towards the rear end side,
• wherein a clamp screw engaged with the one jaw portion is screwed into the holder while inclining in a direction separated from an imaginary plane as it moves towards the other jaw portion, the imaginary plane extending along an extension direction of the slit and in the direction of a bisector of a V-shape formed by the pressing surface and the V-shape formed by the pedestal surface, whereby the one jaw portion is enabled to elastically deform towards the other jaw portion by using as a fulcrum a connecting portion of the pair of jaw portions formed between the rear wall surface of the slit which faces the tip side, and the rear end surface of the head member body located on the extension direction of the rear wall surface, and
• wherein the width of the connecting portion along the extension direction is formed so as to become gradually wider in a direction from one side surface of the head member body towards the other side surface pressed by the head member body when the head member is mounted on the tip portion of the holder,
• the connecting portion is formed so that the rear wall surface and the rear end surface intersect each other within a range of 5° to 15° in a cross-section along the extension direction of the slit in the rear wall surface and,
• the slit has a bent portion in the rear end portion which is provided so as to extend towards the rear end side while being bent towards the one jaw portion.