Cutting tool, insert holder and insert

A cutting tool secured by a first end to a rotary drive device and rotated about an axis by the rotary drive device to cut a workpiece, comprising:

• an insert holder having the first end and a second end at opposite ends;
• and
• a plurality of inserts detachably held in the insert holder, wherein
• the insert holder includes a body having a plurality of grooves formed on an outer circumferential surface, the grooves being closed on a first end side, and open on a second end side, and
• a lid to be attached to the second end side of the body,
• the inserts include base portions to be inserted into the grooves, and
• cutting portions that cut the workpiece, the cutting portions sticking out from the outer circumferential surface of the insert holder while the base portions are held in the grooves,
• wherein the inserts include the base portions and the cutting portions formed in one piece,
• the body includes first projecting portions that are spaced a predetermined distance apart from groove bottoms of the grooves and project from the first end side of the grooves toward the second end,
• the lid includes second projecting portions that, when the lid is attached to the body, are spaced a predetermined distance apart from the groove bottoms, and project toward the first end,
• the base portions include first retaining portions that are interposed between the groove bottoms and the first projecting portions, and
• second retaining portions that are interposed between the groove bottoms and the second projecting portions,
• the first projecting portions have first projecting faces on a side of the first retaining portions, the first projecting faces being angled toward the groove bottoms as they extend toward the first end,
• the second projecting portions have second projecting faces on a side of the second retaining portions, the second projecting faces being angled toward the groove bottoms as they extend toward the second end,
• the first retaining portions have first retaining faces making surface-contact with the first projecting faces,
• the second retaining portions have second retaining faces making surface-contact with the second projecting faces,
• the grooves are spaced apart from each other in a circumferential direction of the insert holder,
• the second projecting portions are disposed discontinuously in the circumferential direction of the insert holder, such that the second projecting portions are inserted into the grooves upon attachment of the lid to the second end side of the body,
• the lid has an outer diameter smaller than that of the body,
• the second projecting portions project into the grooves,
• ends of the cutting portions of the inserts in a direction parallel to the axis are coplanar with the second end of the insert holder, and
• the base portions of the inserts include peripheral portions located inside the grooves and outward from the second projecting portions in a direction perpendicular to the axis, the peripheral portions being contiguous with the cutting portions.