Impact Drill vs Hammer Drill

An impact drill is a type of reciprocating tool that utilizes an impact or hammering force on the drill chuck to drill through hard or brittle substances such as concrete or tile. There are two basic varieties of this type of tool. These two basic varieties are the impact drill and the hammer drill. While the basic operation of these two tools is quite similar, they are usually used under different circumstances. Below are two paragraphs that give basic descriptions of these two tools and some common uses for them.

Drill Operation

Impact and hammer drills drill through hard substances such as concrete and tile using a rotary hammering action. The main chuck rotates while another mechanism causes a hammering action against the chuck. In the heavy duty rotary hammer or hammer drill, this secondary mechanism is a piston, while in the lightweight impact drill, an eccentric flange and spring assembly creates the hammering action. This hammering action breaks up the material being drilled, while the rotation of the bit causes the bit’s flutes to remove the pulverized material. Most newer impact drills and rotary hammers have switches which increase or decrease the speed and torque and also turn the hammering action on and off.

Impact Drill

The operation of a hammer drill, also known as a rotary hammer, is quite simple. A rotary motor rotates the drill chuck while a spring and flange assembly causes the hammering action. As the tool rotates, the flange pulls the drill’s chuck back towards the handle. At a specific point, the flange releases the chuck, and a spring causes the chuck to move forward and hammer against the material being drilled. Being smaller and lighter, impact drills can be used for extended periods of time and at angles and heights.  Impact drills are used mostly on tile or sandstone because these materials are relatively soft. Impact drill bits are standard, smooth shaft bits, with hardened carbide tips.

Hammer Drill

Hammer drills, or rotary hammers, are the larger cousin of impact drills. For this reason they are used by contractors to drill holes in foundation footings and sandstone. Hammer drills are also chosen when speed is of the essence because of their increased power. Because of the increased weight, it’s recommended to only use hammer drills when the work is at waist level or below to decrease the chances of bodily injury or damage to the tools. Rotary hammers achieve their hammering action from a piston instead of a flange and spring assembly. Due to the increased impact forces, rotary hammers, or hammer drills, require special drill bits, with special locking flanges. An added feature of most rotary hammers is the clutch which disengages the motor when the bit becomes jammed in the work. This prevents the drill from being torqued out of the operator’s hands when the bit is jammed, which keeps both operator and tool from being injured or damaged.