In 1975 Bosch were the first manufacturer to launch SDS hammer drills. SDS refers to a Special Direct System and is a drill which uses a specific chuck that does not require tightening. The SDS drills are comparable to standard hammer drills, but have an enhanced hammer action that produces more powerful hammer blows. SDS drills require specially designed drill bits, which are more robust than regular bits and increase safety by reducing the possibility of slips.
The SDS drill has an enhanced hammer action, which means that it can deliver hundreds of times the energy per hammer blow compared to a conventional hammer drill. Also the different chuck design and special SDS drill bits remove the possibility of bit slip. The drills are designed to be able to withstand the force of its hammer action, so the SDS drill bits easily slot into place and are held until released.
The action on SDS type drills is slightly different to that produced by standard hammer drills. The SDS drill bit moves within the chuck itself compared to the more traditional method of having the whole chuck move. This is down to the way the SDS drill bit is held within the chuck, with the SDS drill bit having short grooves running along the length of its body that the chuck clips into. These grooves enable the bit to move in and out and the hammer action is created when force is applied to the end of the bit within the chuck. This means that power can be directed much more precisely and efficiently and results in better performance when trying to drill through tougher materials. Rotary stop is available on certain SDS Drills, which means that the rotary action can be switched off, leaving just the hammer action and therefore lets the drill be used as a demolition or breaker hammer with an appropriate chisel bit.
