Nearly drill bit reamer

The utility model relates to a nearly drill bit reamer, the central authorities of reamer body have along the fluid passage of its axial through front end and rear end, evenly be equipped with on the lateral wall all around of reamer body and a plurality ofly link up in fluid passage's installation space, install reaming device among each installation space respectively. Reaming device includes enlarger and protecting cover, the protecting cover is fixed on reamer body outer wall, and the enlarger can be provided in the corresponding protecting cover to the reamer body circumference outside under the effect that receives well drilling hydraulic pressure force with stretching out. Fluid passage's rear end be equipped with with bumping of dropping into press the ball keep off suppress in fluid passage pressures, and the seat valve formula that makes the drilling fluid pass through of sliding backward bump pressure ball backstop device. The utility model discloses can according to particular case select reaming hole operation mode or while creeping into reaming hole operation mode, the reaming hole is effectual.