When you are boring into concrete or brick, the shank on your bit matters as much as the tip. SDS drill bits and regular round-shank masonry bits are built for two very different drilling systems, and matching the bit to the drill is the key to fast, clean holes.
What SDS Actually Means
SDS stands for Slotted Drive System (sometimes called Slotted Drive Shaft). Instead of a smooth round shank clamped by a three-jaw chuck, an SDS bit has open slots along its shank that lock into a spring-loaded SDS chuck. This lets the bit slide back and forth a few millimetres so the hammer mechanism can strike the bit directly, delivering far more impact energy than a standard hammer drill.
Regular Masonry Bits
A standard masonry bit has a round or hex shank and a carbide-tipped cutting edge brazed to a spiralled steel body. It fits any keyed or keyless chuck, so it works in an ordinary cordless drill or a hammer drill. The carbide tip crushes and grinds masonry rather than shearing it like a twist drill cuts metal, and the flutes carry the powdery dust up and out of the hole. Because they clamp in a normal chuck, these bits are the everyday choice for homeowners and general trades who do not own a dedicated rotary hammer.
Impact Energy Is the Real Difference
A hammer drill vibrates a round-shank bit forward using a pair of ridged clutch plates. That works for small holes in brick and soft block. An SDS rotary hammer uses a piston to hammer the bit with much greater force per blow, so it powers through hard concrete and rebar-tough footings with less effort and heat.
- Round-shank masonry: best for holes up to roughly 12mm in brick, mortar and light block.
- SDS-plus: the most common rotary-hammer standard for general concrete work and anchors.
- SDS-max: a larger shank for heavy demolition and big-diameter holes.
Which Should You Choose?
If your work is occasional and light — hanging a shelf on a brick wall, mounting a hose reel — a quality round-shank masonry bit in a hammer drill is plenty. If you regularly set anchors in structural concrete, an SDS rotary hammer and SDS-plus bits will save your wrists and your workday. Note that the two are not interchangeable: an SDS bit will not clamp in a standard chuck, and a round bit will not lock into an SDS chuck without an adaptor. If you think you will grow into heavier work, buying the rotary hammer first often makes more sense than replacing a hammer drill later.
Getting the Best Life From Either Bit
Let the tool do the work. Pushing too hard overheats the carbide tip and dulls it fast. Pull the bit out periodically to clear dust from the hole, and keep a steady, moderate speed. American-made carbide-tipped bits hold their edge well, but even the best tip benefits from clearing the flutes so cuttings do not pack and bind. Match the bit diameter to your anchor and you will get holes that hold.