Twist drill is a tool to drill a round hole of a workpiece through its rotary cutting relative to a fixed shaft. It is named because its chip groove is spiral and looks like a twist. Spiral grooves have 2 grooves, 3 grooves or more, but 2 grooves are the most common. Twist drills can be clamped on manual and electric hand-held drilling tools or drilling machines, milling machines, lathes and even machining centers. The drill bit material is generally high-speed tool steel or cemented carbide.
An impact drill works by rotation and impact. A single impact is very slight, but an impact frequency of more than 40,000 times per minute can generate a continuous force. Can be used for natural stone or concrete. When the impact drill works, there is an adjusting knob at the bit chuck, which can adjust the common hand electric drill and impact drill. The impact drill uses the gears on the inner shaft to jump each other to achieve the impact effect, but the impact force is far less than that of the electric hammer. It is not suitable for drilling holes in reinforced concrete.