Most drills are made from round bars of tool steel hardened and tempered to suit the work to be performed, generally to a dark straw color. The flat drill is made in the shop and is used because it is Cheap. It is impossible to drill a hole accurately with a flat drill, although such a drill does very well for rough work in the boiler or smithshop. The flat drill was the first form of drill made, but later it was found to wear out quickly and require frequent grinding. Thus the cutting edge or lip wore away so rapidly that the drill soon had to be redressed (made over) by the tool-maker. To overcome this fault the lips were twisted into a curve or spiral. This improvement was found to give a cutting edge which did not change its shape when the drill was reground. Thus it is evident that the twisted flat drill led to the fluted twist drill and later to the flat twist drill. The former drill is a round bar of tool steel having two straight grooves or flutes cut on opposite sides. This form of drill is used for drilling in brass, copper, or Babbitt metal.