What Does SDS Mean?

SDS is the name of the bit-and-chuck system used by rotary hammer drills. Bosch developed it in 1975, and the letters originally stood for the German phrase Steck, Dreh, Sitzt: insert, twist, and it sits. In English-speaking markets Bosch called it the Special Direct System, and you will also see it described as the Slotted Drive System or Slotted Drive Shaft. All of these names describe the same idea: a drill bit shank with slots and grooves that locks into the chuck without a chuck key.

How the SDS shank works

An SDS shank has two sets of recesses. Two open grooves let ball bearings in the chuck drive the bit round, transmitting the turning force. Two closed slots capture locking balls that stop the bit falling out, while still allowing it to slide backwards and forwards by around a centimetre. That sliding movement is the clever part: the hammer mechanism inside the drill can fire the bit forward directly, rather than shaking the whole chuck, which is what makes a rotary hammer so much more effective than an ordinary hammer drill. Fitting a bit takes a second: push it in, twist slightly until it clicks, and pull the sleeve to release it.

SDS-Plus, SDS-Max and SDS-Quick

SDS-Plus replaced the original SDS shank and is fully compatible with it. The shank is 10mm across with four grooves, and it is the standard on every mainstream rotary hammer. Bits run from about 4mm up to 26mm, with chisels, gouges and light breaker steels widely available. Browse our corded and cordless SDS-Plus drills.

SDS-Max uses an 18mm shank with five deeper grooves, built to carry the much harder blows of heavy-duty machines. It suits drilling from about 12mm to 52mm, core bits and full-size demolition chisels. SDS-Max and SDS-Plus bits are not interchangeable, so choose the system before you build up a bit collection. See our corded SDS-Max and cordless SDS-Max ranges.

SDS-Quick is a smaller Bosch-only shank used on compact 12v-class tools. Its party trick is that the same holder also accepts standard quarter-inch hex screwdriver and drill bits, making a genuinely pocketable drill-and-driver for light masonry. Details in our SDS-Quick category guide.

Can I use ordinary bits in an SDS drill?

Yes, with an adaptor. Many SDS-Plus drills come with a keyed or keyless chuck adaptor that accepts straight-shank bits for drilling wood and steel; some models have a quick-change chuck built in. Switch the drill to rotary-only mode first, because hammer action wrecks both ordinary bits and adaptor chucks. Our guide to SDS drill settings explains each mode.