hack hammer

A hammer terminating at each end in an obtuse chisel-edge, kept in order on the grindstone. It is used as the peen of an ordinary hammer, but is narrower, and d therefore more local and energetic in its effects. The hack-hammer for reducing unequal protuberances on grindstones is shaped like an adze and has a short handle. When the grindstone has worn unequally, it becomes nece ary to dre it, and the high places, being marked, are hacked by oblique and cro ing checker lines, which cause it, on the next grinding operation, to wear more at these points, and thus restore equality.