| 摘要 |
FIELD: construction. ^ SUBSTANCE: annular drill comprises a tubular casing made as slotted in the form of tabs with cutting teeth at the end, and a tail. Slots at the end along the width exceed width of teeth and taper to the tail, at the same cutting teeth are arranged in the form of trapezoidal plates, having ledges at the edges at the inner side and ribbons at the outer side rounded along arcs of appropriate circumferences. Teeth may be arranged as double-bladed with opposite symmetrical blades having a common concave rear surface. ^ EFFECT: higher resistance of a drill, increased feed and depth of drilling. ^ 2 cl, 4 dwg |
