Roller bit tooling - triple roller with studs pyramid studs and teeth for crater, ring and wedge-out action at high penetration rates

摘要

First roller has studs arranged to produce rings of isolated indentations or small craters, second roller has truncated pyramid studs to join the craters into continuous concentric rings or rows. Third roler has teeth shallower than the first tw which break out the rock remaining between the furrows or traces produced by the preceding two rollers. All teeth and studs are tipped in hardmetal and the studs or teeth on the first two should be higher in order that the third roller teeth force the drillings into the relatively deeper furrows left by the preceding teeth thus assisting in drillings removal and ensuring pentration by one tooth depth per revolution.