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Choose the SDS bit by the hole, the material and the hammer—not just the diameter
For ordinary concrete and brick, a two-cutter carbide SDS-Plus bit is the practical choice; for frequent drilling, tougher concrete or a better chance of encountering rebar, choose a four-cutter head, and match SDS-Max to a rotary hammer built for larger, deeper holes. A four-cutter head can tolerate incidental contact with reinforcement better, but no standard masonry bit should be used to drill through steel rebar.
SDS describes the slotted shank that locks into a compatible rotary hammer; it does not describe the carbide head or guarantee that a bit suits every masonry job. Before buying an SDS drill bit or a set, check three things: the tool’s SDS-Plus or SDS-Max chuck, the hole diameter and depth, and whether the work is plain masonry or reinforced concrete.
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Two cutters or four?
| Head design | Typical use | What happens at rebar | Best fit |
|---|---|---|---|
| Two-cutter carbide | General holes in brick, block and concrete | Can chip or snag if it hits steel; stop rather than forcing it | Occasional work, small-to-medium anchors and a lower-cost replacement bit |
| Four-cutter carbide | Repeated drilling, harder concrete and more demanding sites | More balanced cutting and improved resistance to damage from incidental contact; it still is not a steel-cutting bit | Frequent use, reinforced concrete where permitted, or when hole consistency matters |
Two-cutter bits are often adequate for routine anchor holes. Their simpler head is commonly less expensive, but the cutting edges may wear or break sooner under heavy use. Four-cutter heads distribute cutting across more carbide edges, helping the bit cut more evenly and reducing the risk that an accidental hit on reinforcement destroys the head. The actual result depends on carbide quality, head geometry, concrete and drilling technique—not cutter count alone.
If the bit stops advancing, the hammer tone changes, or steel is visible, release the trigger. Don’t lean harder or keep hammering: that can overheat or damage the carbide and the tool. Confirm the reinforcement location and follow the project’s requirements. If the hole must pass through steel, use an appropriate metal-cutting method and bit, or consult the engineer or anchor manufacturer. Do not assume a four-cutter masonry bit can cut rebar safely.
SDS-Plus vs. SDS-Max: choose by tool and hole scale
| Shank system | Common bit diameter range | Typical bit length examples | Usually suited to |
|---|---|---|---|
| SDS-Plus | About 4–30 mm | 110, 160, 210 and 260 mm overall lengths are common | Smaller rotary hammers, anchors and everyday drilling |
| SDS-Max | About 12–52 mm | 340, 520 and 920 mm overall lengths are common | Larger rotary hammers, larger-diameter holes and deeper work |
These are representative ranges, not universal limits: each bit and hammer has its own rated capacity. Check the tool manual, especially for large diameters and core-style drilling. SDS-Plus and SDS-Max shanks are not interchangeable. A larger SDS-Max bit will not fit an SDS-Plus chuck, and an adapter is not a substitute for a hammer with the right capacity.
For a few small holes for wall plugs or light-duty anchors, SDS-Plus is usually easier to handle and more economical. If you regularly drill larger holes, work in thick concrete or need long-reach bits, SDS-Max is the appropriate system—but only with a compatible rotary hammer rated for that work. A long bit can flex, wander or bind more readily, so use it only when the depth requires it.
Pick by job: a practical decision guide
| Your situation | Recommended starting point | Why |
|---|---|---|
| A few small holes in brick or block | SDS-Plus, two-cutter bit | Low-cost, readily available choice for occasional masonry drilling |
| Repeated anchor holes in concrete | SDS-Plus four-cutter bit, if the diameter is within tool limits | Better suited to repeated work and more consistent cutting |
| Hard concrete or frequent site work | Four-cutter bit matched to the hammer’s system and capacity | Durability and drilling consistency matter more when the bit sees sustained use |
| Large or deep holes | SDS-Max if the hammer and bit are rated for the diameter and depth | The shank and tool class suit heavier drilling; use the shortest bit that reaches |
| Likely rebar in the hole path | Locate reinforcement first; use a suitable four-cutter masonry bit only for permitted concrete drilling | It may handle incidental contact better, but it does not replace a steel-cutting bit or project approval |
Depth, diameter and bit-set buying checks
Buy for the hole’s required usable depth, not just the wall thickness. Bit listings may state overall length, while the working or flute length—the portion that can clear debris and drill effectively—is shorter. For a deep anchor hole, confirm the manufacturer’s usable drilling depth and the anchor specification. Leave room for dust at the bottom, and don’t count on the very tip of a long bit to provide the full stated depth cleanly.
A set is worthwhile when it covers the diameters you use repeatedly. A compact SDS-Plus set might include 6, 8, 10 and 12 mm bits in lengths around 110–260 mm; a larger set may add longer bits or more sizes. Treat those as examples, not a standard. Check that every bit uses the right shank, has useful working lengths, and includes the diameters your anchors actually require. A large assortment of rarely used sizes is not better value if the common bits are poor quality.
As a rough ownership calculation, compare the set premium with likely replacement needs: if a four-cutter bit costs about twice as much as a basic two-cutter bit but lasts more than twice as many equivalent holes in your conditions, it costs less per hole. There is no dependable universal lifespan, though—abrasive aggregate, hitting steel, dust buildup and excessive pressure can change wear dramatically. For occasional home repairs, paying extra for a full premium set may not make sense; for repeated work, replacing fewer damaged bits can justify it.
Use and maintain the bit to protect the carbide
- Check the shank and chuck: Clean off grit and confirm the bit locks into the correct SDS system. A damaged or dirty shank can prevent proper engagement.
- Use hammer drilling only in suitable masonry: Follow the tool maker’s guidance for mode, diameter and duty cycle. Don’t use hammer action on tile or other brittle finishes where impact may cause cracking.
- Start square and let the hammer work: Keep the bit aligned and use steady pressure. Forcing it can overheat the head, strain the hammer and produce an oversized or crooked hole.
- Clear dust during deep drilling: Withdraw the bit periodically to help remove debris. Packed dust slows cutting and increases heat; use suitable dust extraction or protective measures for the material and worksite.
- Inspect and store clean: Stop using a bit with chipped carbide, a bent body or a badly worn shank. Brush off dust and store it dry so grit and corrosion don’t damage the cutting head or chuck.
For most occasional concrete and brick jobs, a correctly sized SDS-Plus two-cutter bit is enough. Move to a four-cutter head when drilling frequently or when concrete is demanding, and choose SDS-Max only when the hole scale and compatible hammer call for it. If reinforcement is present, treat it as a separate engineering and tooling question—not a reason to force a masonry bit through steel.