From Dynadrill Equipment@21:1/5 to All on Tue May 15 04:40:36 2018
Dynadrill O-Dex systems for DTH hammers are designed to drill and case simultaneously through overburden, passing easily through large boulders, pulling lightweight, inexpensive casings behind them. On reaching the bedrock or required depth, the drill
string is removed easily from the hole, leaving the casings in place. Drilling into the bedrock can then be continued using a normal drill bit.