A down-the-hole drill, usually called DTH Drilling Rig, is basically a mini jackhammer screwed on the bottom of a drill string. The speedy hammer activity breaks hard stone into little flakes and dust and can be dismissed evident by the air exhaust in the DTH hammer.
[pdf] Unplug the Dremel and attach the appropriate sized drill bit. Begin drilling the material with the Dremel set on a slow speed. Hold the Dremel perpendicular to the material at all times. Once you start the hole, you can increase the speed to quicken the drilling process.
[pdf] A complete range of accessories for large diameter drill rigs, including kelly bars, CFA augers, drilling equipment and tools, designed to support the full spectrum of large diameter drilling methodologies in all types of soil.
[pdf] 
