Countersinks can oftentimes be mistaken for counterbores. The difference between these two shapes is that countersinks are used to cut conical holes into materials while counterbores feature flat-bottomed holes either flushing into a material or below it. Countersinks are available as hand reamers or flutes to use on wood, aluminum, plastic, steel, brass, and more. Shop at Jantz Supply for all your knifemaking needs.