Special direct system drills are often referred to as SDS drills. These drills are designed for use with several types of drill bits, including hammer drill bits. Most hammer drills operate by moving a chuck — the hollow channel into which a drill bit locks — back and forth to produce a hammer action. An SDS drill employs bits that feature a groove system that allows these chucks to stay in place while still providing drilling and hammering actions. An SDS drill bit is thought to provide more efficient drilling and hammering action than a regular hammer drill bit does.
The shank on an SDS drill bit features a set of specially designed grooves to give the bit rotary force. Closed channels along the shank are designed to accommodate roller balls, which allow SDS drill bits to move back and forth, providing hammer action. These bits allow for quick, nearly seamless bit changing; tools and chuck keys are not needed to change out these bits.
SDS drills are more powerful. They generally offer higher torque output and operate more efficiently than the average hammer drills on the market. They are also safer because their stationary chuck design reduces slips. A stationary chuck allows the more accurate direction of power from drill to workpiece. An SDS hammer drill system can drill through hard materials such as concrete and brick much more quickly than the average hammer drill system. Despite the increase in performance, these drills usually operate much quieter than regular hammer drills.
SDS drill bits are designed for hammer drilling applications on harder materials such as brick, granite and marble. They have to be durable enough to withstand hammering applications while drilling, which is why most manufacturers construct their SDS drill bit models out of tough, durable materials such as tungsten carbide. This is one of the the hardest materials on Earth.
Material hardness can be measured using the Moh's scale, which offers values from one to ten. Diamonds are the hardest material on Earth, they offer a value of ten on this scale. Tungsten carbide is also a very hard material with a hardness value of around nine. An SDS drill bit formed out of tungsten carbide can easily drill through and chip away materials such as brick, concrete, and granite, all of which offer lower hardness values than tungsten carbide.
Drilling and hammering through concrete and other hard materials produces a large amount of dust and debris. Wearing a dust mask or respirator system helps SDS drill operators keep potentially harmful airborne debris from entering their lungs while drilling. The loose chips and debris produced by drilling through hard materials can also damage the eyes. SDS drill operators should wear goggles, masks, or other safety equipment to prevent eye damage while drilling with an SDS drill.