Detachable insert-type cutting tool

A detachable insert-type cutting tool, comprising:

• a holder;
• a head member which has an insert seat on which a cutting insert is detachably mounted and which is detachably attached to a head portion of the holder so that an attachment surface of the head member is closely in contact with an attachment surface of the holder;
• a coolant hole which is formed inside the holder so as to be opened on the attachment surface of the holder;
• and
• a first groove which is formed on the attachment surface of the head member, communicating with the coolant hole opened on the attachment surface of the holder and extending so as to be opened toward a cutting edge of the cutting insert mounted on the insert seat, wherein a second groove extending along the first groove of the head member is formed on the attachment surface of the holder so that a coolant passageway is defined between a surface of said first groove and said second groove to be opened toward the cutting edge of the cutting insert.