To solve the problem that burdens during widening work of a large diameter part are large.
A widening and drilling device includes a base part 1 disposed at a distal end of a pipe P and a plurality of openable and closable widening bits 2, 2a... attached to the base part 1, has a water conducting hole 3 formed in a center longitudinal direction of the base part 1, has jet holes 4 and 4a that are communicated with the water conducting hole 3 and are capable of jetting water inside a drilling part H, is insertable into the drilling part H in the state of closing the widening bits 2, 2a..., and is capable of partially widening the drilling part H by opening the drilling bits 2, 2a... inside the drilling part H. After the widening and drilling device is inserted into the drilling part H formed in the soil in the state of closing the widening bits 2, 2a..., the widening bits 2, 2a... are opened at a widening part in the drilling part H, the widening and drilling device in the state of completely opening the widening bits 2, 2a... is repeatedly moved back and forth while being rotated, and a part of the drilling part H is widened to form a large diameter part Hb. Thus, by partially forming the large diameter part Hb while gradually scraping a hole wall of the drilling part H of a small diameter formed beforehand, burdens during the widening work are reduced.
YAMADA MAKOTO
OTSUKI TADAYUKI
HATTORI KEIJI
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