Spade drills. Spade drills are used for drilling large holes of 3.5 in.(90mm) or more. Their design results in a marked saving in cost of the tool as well as a tangible reduction in its weight, which facilitates its handling. Moreover, this type of drill is easy to grind.
扁平钻。扁平钻用于钻削3.5英寸(90毫米)或更大的大孔。其设计使得钻头成本明显节省、重量切实减轻?重量轻又使操作更方便。此外这种钻头容易磨利。