| 摘要 |
PROBLEM TO BE SOLVED: To provide a cylindrical drilling blade, being high in mechanical strength, applicable to a single acting type and also autorotation type drilling device, also advantageous even to productivity and manufacturing cost, excellent in sharpness, and smaller in drilling resistance, by solving the problem on a conventional sheet metal hollow blade.SOLUTION: The cylindrical drilling blade is formed with a cylindrical part of combining a recessed part formed by butting of two side edges of a metal plate and formed on one side edge of the metal plate and a projection part formed on the other side edge of te metal plate in response to the recessed part, in a cylindrical surface and an edge part formed on one end in the axial direction of the cylindrical part. Desirably, the recessed part and the projection part become a dovetail joint, and the edge part is formed as two or more of pointed head blades or the edge part is formed as a waveform blade. |
