The invention relates to a soft
coal seam one-time hole forming while-drilling casing device. The soft
coal seam one-time hole forming while-drilling casing device comprises a multi-stage
reamer bit, wherein a blade contraction mechanism is arranged on the right surface of the multi-stage
reamer bit, a rotary casing dragging mechanism is arranged on the right surface of the blade contraction mechanism, and the blade contraction mechanism comprises a first
butt joint sleeve. According to the soft
coal seam one-time hole forming while-drilling casing device, the multi-stage
reamer bit and the blade contraction mechanism are arranged, the multi-stage reamer bit can achieve the effect that multiple times of reaming can be completed through one bit and one-time drilling, disturbance to the hole wall is reduced, the hole
exposure time is greatly shortened, and therefore the hole collapse probability is greatly reduced; if hole wall collapse occurs in the drilling process, a casing following the bit can support collapsed crushed coal outside the casing, and drilling accidents such as drilling tool falling and breaking,
drill jamming and
drill burying cannot be caused; and the casing can be pulled back and forth to crush coal briquettes, the crushed coal briquettes are discharged out of holes through
drilling fluid, and local hole collapse can be treated.