Manufacturing method of expanded hole bit of rhombus pantograph specification and expanded hole bit of rhombus pantograph specification capable of adjusting the hole diameter

摘要

To provide an expanded hole with a large diameter which is forcibly and mechanically expanded without relying on a target ground with regard to a hole expansion bit which expands the diameter of a fixing part by setting a fixing mechanism of a ground anchor to an expanded hole support pressure strut type.SOLUTION: A hole expansion bit of rhombic pantagraph specifications comprises: a cutter 1 for an expanded hole which is attached to a hole expansion bit body and can be bent by connecting a center portion using a connecting pin 16; a cutter fixing tool 2 in which a drive shaft 4 is passed through the cutter and which fixes a hole bottom-side end portion of the drive shaft; a guide pipe 3 in which a hole bottom-side end portion of the cutter 1 is attached to the cutter fixing tool; and a cutter moving tool 5 which can be bent by connecting an end portion of the ground surface-side cutter. The hole expansion bit is configured such that: a concave portion is formed in the cutter moving tool and a convex portion is formed in a part of the drive shaft 4; the concave portion of the cutter moving tool and the convex portion 25 of the drive shaft are fitted with each other; the cutter moving tool and the drive shaft can be slid while maintaining the axial direction; a ground surface-side end portion of the drive shaft is fixed; and the cutter and its coupling portion 26 can be raised on a circumference of the cutter moving tool when the cutter moving tool is slid.SELECTED DRAWING: Figure 4