Method of drilling conical hole for expandable bolt anchor - uses barrel in pilot bore to align bit for further bores angled to pilot bore

摘要

The drilling method form a conical hole for an expandable bolt anchor in concrete or masonry, entailing boring of a cylindrical pilot hole (4) on the cone axis (A-A). A series of evenly distributed holes are bored each at a specified angle to the pilot hole and intersecting on the root of the expandable anchorage cone. A barrel (1) with one or more angled guide holes may be positioned in the pilot bore and is used to guide the bit (2,42) forming the angled bores. It has a flange (46) limiting its penetration. The barrel may have one inclined guide hole (3) only, being rotated by a hand-lever (14) to vary the position of the inclined bores.