Rob, blackdave is right, it is a simple form of a drill. You might think of this as the more commonly see post drill stripped down to it simplest form. These were not intended for drilling very deep holes. I have seen these mounted both vertically and horizontally, though vertically makes more sense to me. The adjustable fork on the bottom end was for hold the drill table, which was a round plate of iron with a shaft about 4" long on one side to locate it between the fork tines. This drill would have been much less expensive than the tradition geared flywheel post drill, so you might think poor blacksmith or farm shop. A gunmaker could have used it, but it wasn't suitable for barrel drilling.