The invention nails insertion hole expansion device, and relates to the method, in particular nails as insertion of the rock drill to be mounted on a rotating rod for drilling a hole, the support plate 1 before and after the pair facing each other, see provided on the rotating rod; A plurality of projections that spread the drilling day dolseol at equal intervals on the rotating circumference load; A hinge coupled to the lower front and rear pair of the support plates, a plurality of excavating day abuts the protrusion spread selective deployment possibly composed in accordance with the rotation direction; Characterized in that comprises a. According to the invention, the nails insertion hole perforated by a cross-section at least in one place over extended, this by the over extended grout to be formed, with increasing the economical efficiency by reducing the overall effective length of the nails inserted balls, nails rear portion of the frictional force and not by increasing the pressure by ensuring a sufficient pull-out resistance can be obtained the effect to improve the stability of the compaction features and weak points due to the pressure of the soil grouting. Nails, ball inserted, rock drills, drilling bits, reinforced beams, grout, rotating rod, digging day