Down-the-hole drill bit

with buttonsfor rock

Concentric overburden drill system Brief introduction of Concentric overburden drill system The concentric overburden drill system consists of three parts: central pilot bit, casing shoe and symmetrical ring bit. The central pilot bit drills away the center part of the hole and guides the drill string, incorporated with a sacrificial symmetrical ring bit make a full face drill bit. The casing shoe is welded or threaded to a casing pipe, which is pulled down by the impact of the DTH hammer and central pilot bit. The symmetrical ring bit and casing shoe assembly is locked into central pilot bit with a hammer shank, and the ring bit is to drill the segment the casing to advance down the hole. The pilot bit’s upper shoulder engages the shoulder of the casing shoe. DTH hammer’s impact energy is transferred through the pilot and ring bits, crushing rock, part of impact energy advances casing. On completion of drilling and casing, the drill string with pilot bit is retrieved by a slight reverse rotation to unlock the bayonet coupling. The ring bit stays in the hole, and can be recovered only if the casing is retrieved. Drilling continues to the desired depth in the bedrock using a conventional drilling. Drilling through loose, unconsolidated material such as soil, clay, silt, sand, gravel, and boulders is the so-called overburden, which is often problematic due to the tendency of the earth to cave in behind the drill bit. The Symmetric Casing Drilling System is just to drill in rock formation where contains some such ovals and fractures, and it represents the latest technology in simultaneous overburden casing drilling systems.