| 摘要 |
A reamer for drilling a hole having a diameter larger than a pass through diameter in one aspect includes a body having reaming blades affixed at azimuthally spaced apart locations. These blades have cutters attached at selected positions. An outermost surface of each blade conforms to a radially least extensive one, from a longitudinal axis of the reamer, of a pass through and a drill circle, The drill circle is substantially coaxial with the axis. The pass-through circle is axially offset from the drill circle and defines a section wherein the pass-through circle extends from the axis past the drill circle, so that cutters disposed on the reaming blades in the section drill at full drill diameter, while avoiding wall contact at the pass-through diameter. In another aspect, the reamer includes a pilot hole conditioning section including azimuthally spaced apart blades affixed to the body longitudinally ahead of the reaming blades. The pilot blades include a taper at their downhole end, a gauge pad having a diameter substantially equal to the drill diameter of a pilot bit longitudinally ahead of the reamer, and at least one intermediate cutter affixed longitudinally behind the gauge pad. The intermediate cutter is laterally positioned to drill a hole having an intermediate diameter larger than the pilot hole and smaller than the reamer drill diameter. The pilot blades include an intermediate gauge pad having a diameter substantially equal to the intermediate diameter.
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