A NEW TECHNIQUE FOR PREPARING ROCK SPHERES

Since spherical specimens are of optimum shape for measuring the directional properties of rock, increased use of rock spheres for rock mechanics research is anticipated. Hence, a need arises to reduce the time required to prepare rock spheres. A new sphere preparation technique which reduces sphere preparation time to about half that required by conventional techniques was developed at the Bureau of Mines' Twin Cities Mining Research Center. In the new technique, the rock specimen is core drilled in three mutually orthogonal directions and its remaining edges and corners ground on a grinding wheel, before being placed in a sphere grinding machine for final grinding and polishing. The new technique permits closer control of specimen diameter than was possible by former sawing procedures.