| 摘要 |
A hole coring system is provided that greatly stabilizes a tubular core drill bit for drilling into concrete or other materials enabling large diameter holes to be drilled with a handheld tool. The hole coring assembly includes a hollow drive shaft assembly that fits over a stationary mandrel that is initially installed and anchored in a pilot hole in the concrete or other material. Once the mandrel has been firmly installed as a guidepost extending rigidly out from the concrete surface, the hollow drive shaft assembly is lowered onto the mandrel. The drive shaft assembly is stabilized relative to the mandrel by means of elongated, cylindrical bearing sleeves, which may be formed of self-lubricated or fluid lubricated bearing materials. The mandrel serves as a central guidepost that ensures that a relatively large diameter, tubular core drill bit remains precisely centered relative to the guide mandrel. This enables the operator to use a commonly available tool to rotate the drill and apply drill pressure only. Preferably a releaseable latch and catch mechanism is provided to releaseably couple the drive shaft assembly to said mandrel.
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