DRILL WITH CHIP EJECTING COVER

PURPOSE: To eject chips without deteriorating surface roughness of the finished surface of a hole. CONSTITUTION: A cylindrical cover, the outside diameter D2 of which is the same as the outside diameter D1 of a cutting edge 4a or slightly smaller than that, is fixed to the outer peripheral surface of a shank 3. Stepped parts 9, 10 having slightly reduced diameters are formed on the rear side in the direction of rotation of the cutting edge, and an engagingly locking part 18 at the tip of the cover is engagingly locked to the stepped parts. A recessed part 19, which is notched in the shape of a recessed curved surface in order to avoid the loading part of a tip 4, is provided at the tip of the cover. Further, the area facing the chip ejecting grooves 6, 7 at the tip of the cover, especially the area inclined in the direction of thinkness from the outer peripheral surface toward the inner peripheral surface is chamfered. An oil hole is drilled on the flank of the cutting ege 4a.