BORING TOOL WITH THREE OR MORE CUTTING BLADES

摘要

PURPOSE:To provide a boring tool which can easily open a preparatory hole in a panel of formed concrete or the like, by shaping the cross section of the body of the tool continuous to its shank as a polygon and mounting cutting blades on the sides of the body of the bit so that the blades can be spread. CONSTITUTION:Clamping bolts 10 for a boring tool 1 are loosened. Three cutting blades 9 are inclined at the same angle in the direction of an arrow P centering the bolts 10. The bolts are tightened so that the cutting blades 9 are firmly secured on the sides of the body 4 of the boring tool 1 at an inclination angle of theta to the axis C-C the tool. The sharp-pointed tip 5 of the body 4 is thrusted to a desired position in a workpiece W to bore a preparatory hole G. The hole is enlarged by the cutting edges 13 of the cutting blades 9. A hole H with a desired diameter of D is thus opened.