Analysis of seam hole deflection patterns

Summary

• 1. The drilling tool can be guided in the vertical plane by changing the feed force and thus regulating the position of the head in the coal seam.

• 2. The neutral axial force on the head depends markedly on the angle of taper of the bit; by selecting the angle of taper, it is therefore possible to obtain a preferred position of the tool in the seam: at the roof, floor or center of the seam.

• 3. Deflection of the hole in the plane of stratification is not proportional to the diametral clearance between the tool and the walls of the hole, but is governed essentially by the length of the hole and the deflecting force.