SDS Drill vs Combi Drill: Understanding the Difference
Both tools drill holes. Beyond that, they are designed for entirely different jobs, and using the wrong one costs time and damages bits. This guide explains how each works, what it is suited to, and how to decide what to buy.
How Each Tool Works
The Combi Drill
A combi drill (combination drill) combines three functions: rotary drilling, hammer drilling, and screwdriving. The hammer action in a combi drill is produced by two ratchet plates inside the chuck assembly clicking against each other as the chuck rotates. This generates rapid, shallow vibrations — effective for drilling into brick and lightweight block, but limited when it comes to dense materials.
The bit is held in a three-jaw keyless chuck. This is versatile — you can use standard round-shank drill bits for wood, metal, and masonry — but the chuck does not allow the bit to move axially. All impact energy is transmitted through the friction of the jaws.
The SDS Drill
An SDS rotary hammer uses a fundamentally different mechanism. A piston driven by a wobble plate or crank mechanism strikes an internal striker, which in turn strikes the bit directly. This piston-driven hammer action delivers far higher impact energy per blow than a combi drill’s ratchet system, typically measured in joules rather than RPM.
The SDS bit slots into a dedicated chuck where it is locked rotationally but free to slide axially within a small range. This axial freedom is essential — it allows the bit to receive the piston’s impact directly without the chuck absorbing the blow. SDS bits cannot be used in a standard three-jaw chuck, and standard bits cannot be used in an SDS chuck without an adapter (not recommended for hammer use).
When to Use an SDS Drill
Use an SDS drill for:
- Structural concrete — foundations, reinforced slabs, concrete lintels
- Dense blockwork — dense aggregate block, engineering brick
- Natural stone — limestone, granite, sandstone
- Large-diameter holes in masonry — above 12–13mm where a combi drill struggles
- Chasing out — with a chisel attachment, SDS drills in chisel-only mode make light work of chasing brickwork for cables and pipes
- Breaking and demolition — larger SDS tools with flat or point chisels handle tile removal, breaking mortar, demolishing internal block walls
The Makita DHR242 SDS+ rotary hammer is a strong cordless choice for most trade applications. It delivers 2.0J of impact energy in a compact 18V platform, handling the majority of structural masonry drilling encountered on a typical build or fit-out.
When a Combi Drill Is Enough
A combi drill is the right tool for:
- Timber — framing, joinery, furniture construction
- Metal — HSS bits in drill mode, no hammer needed
- Plasterboard and plywood
- Light masonry — fixing a screw into brick mortar or an internal block wall
- All screwdriving — the clutch on a combi drill protects fixings and surfaces
Most screwdriving on site is done with a combi drill or a dedicated impact driver. The DeWalt DCD796 combi drill is a compact 18V brushless tool well suited to a full day of drilling and driving across mixed materials.
For pure screwdriving volume — in timber, through metal brackets — an impact driver is faster and puts less strain on the wrist. A combi drill remains necessary for drilling and for applications where an impact driver’s rotational impact would be inappropriate (such as driving into soft materials).
SDS+ vs SDS Max
SDS+ is the standard for trade work. Bits have a 10mm shank with two open and two closed slots. It handles drilling up to approximately 26mm diameter in concrete, suits most masonry anchoring, cable and pipe routing, and chisel work. The vast majority of SDS drills on the market use SDS+ tooling.
SDS Max has a larger 18mm shank, used in heavier rotary hammers (typically 5kg+). It is suited to large-diameter core drilling (above 80mm with appropriate adaptors), heavy chasing, and demolition work. For most electricians, plumbers, and general builders, SDS Max is unnecessary — the tools are heavier, bits are more expensive, and the additional power is rarely needed.
Cordless SDS Drills vs Corded
Early cordless SDS drills were noticeably underpowered compared to corded equivalents. Modern 18V brushless cordless SDS drills have largely closed that gap for standard trade drilling tasks. The Makita DHR242 and equivalents from Milwaukee and DeWalt perform comparably to a corded tool for most through-wall and anchor drilling.
Where corded still has an advantage: sustained large-diameter core drilling, extended chasing runs, or very hard materials where sustained full-power operation would drain batteries rapidly. For mobile work and most site conditions, cordless is now the practical choice.
Which Should You Buy?
For most tradespeople, both tools are necessary. They are not alternatives — a combi drill cannot replace an SDS for structural masonry work, and an SDS is impractical for timber and screwdriving.
If budget is the constraint, start with a quality combi drill. It handles the majority of day-to-day work across timber, metal, and light masonry. Add an SDS+ drill when the work demands it — typically when fixing into concrete structures, installing masonry anchors, or doing any chasing work becomes a regular requirement.
Buying both from the same 18V platform (battery compatibility across Makita, DeWalt, Milwaukee, or Bosch Professional) avoids the cost of carrying multiple battery systems.
