Abstract: A drill bit reamer stabilizer has an upper and lower stabilizer on a bottom hole assembly with the lower stabilizer as close as possible to the drill bit. This arrangement reduces deviations when drilling a straight hole. Furthermore there is a reamer portion at the leading edge of the lower stabilizer to ensure the drilled hole is reamed out to the nominal drill bit size regardless of drill bit wear. The assembly has a longitudinal shaft with a shank on a top end for connection to a drilling string, an internally threaded box in a bottom end of the shaft for connection to the drill bit, the internally threaded box having an internally tapered lip to overlap a drill bit shank. The lower stabilizer has spiral flutes and lands adjacent the bottom end of the shaft, the flutes have polycrystalline diamond layer inserts at the leading edge of the stabilizer to provide a reamer, the inserts ream a hole substantially the same size as the nominal size of the drill bit.