Importance

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Abstract

A rotary bore hole enlarging bit is connected to a rotary pipe string having a drilling fluid flow path and an actuator flow path. The bit comprises a body structure including inner and outer telescopic body sections, expansible and retractible arms carrying cutters on the outer body section and an expander on the inner body section engageable with the arms to expand the arms and cutters upon telescopic movement of body sections in one relative direction. A piston and cylinder is provided between the inner and outer body sections to secure relative telescopic movement between the body sections. A first passage is disposed in the body structure and expansible arms and cutters for conducting drilling fluid to the cutters from the drilling fluid flow path, there being a second passage in the body structure for conducting actuator fluid to the piston and cylinder from the actuator fluid flow path.

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First Claim