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Concrete edging stones are usually dense, abrasive, and easy to chip at the edge. For a few holes, a standard carbide-tipped masonry bit in a hammer drill is often enough. For repeated holes or especially hard edging, a four-cutter bit or an SDS-Plus rotary hammer can make the work faster and steadier. The right choice depends on the stone, hole size, and drill you already own.
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Choose the bit for the hole and the drill
Most edging-stone jobs use holes around 1/4 to 3/8 inch for small anchors or pins. Check the fastener instructions before buying: the hole diameter must match the anchor, and the required depth may be greater than the anchor’s length. A common rule is to drill about 1/4 inch deeper than the embedment so dust does not stop the fastener from seating.
For occasional work, buy a carbide-tipped masonry bit with a round shank sized for your hole. It fits a standard drill chuck and is usually the least expensive option. Use it in a hammer drill if the stone is hard; in a regular drill, it can work for soft, porous concrete, but progress will be slower.
For frequent drilling, or if your current bits blunt quickly, consider a four-cutter SDS-Plus masonry bit. Its shank fits an SDS-Plus rotary hammer, not a standard three-jaw chuck. The extra cutters can help maintain a round hole and are less likely than a two-cutter tip to snag on aggregate or reinforcement. That advantage may not justify the added cost for just a couple of shallow holes.
Bit and tool options
| Setup | Best for | Trade-off |
|---|---|---|
| Round-shank carbide bit and hammer drill | Occasional small holes in ordinary concrete edging | Affordable and widely compatible; slower in dense stone |
| Round-shank bit and regular drill | Soft, porous stone or a few small holes | Less vibration and chipping, but drilling can take much longer |
| SDS-Plus bit and rotary hammer | Many holes, larger holes, or dense edging | Fast and effective; requires a compatible tool and bits |
| Two-cutter carbide tip | Light-duty, low-cost drilling | More likely to wander or bind in coarse aggregate |
| Four-cutter carbide tip | Repeated holes and tougher aggregate | Costs more; not necessary for every small job |
Drill without cracking the edging
First check that the stone is stable and supported. If it rocks, secure it or improve its bedding before drilling; hammering a loose stone can split it. Keep the hole away from edges and corners. As a practical starting point, leave at least 1 inch between a small hole and an edge, and more for larger holes or brittle stone. Follow the anchor maker’s minimum edge-distance guidance when available.
Mark the center with a pencil or marker. Start slowly with the bit held perpendicular to the surface, then increase speed once the tip has made a shallow seat. This reduces walking and helps avoid a chipped entry. Use hammer mode only when the material needs it. If the bit skates or the stone starts spalling, stop; switch to rotation-only for the first 1/8 inch, then try hammer action again. A piece of masking tape can help keep the mark visible, but it will not prevent cracking.
Use steady pressure rather than forcing the drill. Withdraw the bit every few seconds to clear dust, especially in a deep or narrow hole. Packed dust makes drilling slower and can overheat the tip. If progress stalls, check for a blunt bit or a jammed flute before pushing harder. A two-cutter bit that repeatedly catches in coarse aggregate may be a poor match for the job; a four-cutter bit or rotary hammer can be a better fix.
Speed, heat, and dust
Follow the bit maker’s speed guidance if it provides one. In general, use controlled speed and avoid letting the carbide tip rub in one spot without cutting. If the bit gets very hot, pause and let it cool naturally. Do not quench a hot bit in water; sudden temperature change can damage the carbide or joint. A cordless drill’s clutch should usually be set to drill mode, not a low numbered torque setting. Keep a firm two-handed grip if your tool has a side handle, since a bit can bind abruptly.
Concrete dust is hazardous to breathe. Wear eye protection and a well-fitting particulate respirator, and keep other people away from the dust. A vacuum with suitable filtration or a drill dust-collection attachment is preferable to blowing dust into the air. For a small outdoor job, dampening the surface lightly can reduce dust, but do not pour water around an ordinary cordless drill unless the tool and setup are suitable for wet work.
What to buy—and when to stop
Buy a bit that matches the hole diameter, the drill’s chuck or SDS system, and the material. A masonry bit is not interchangeable with a wood or metal bit: those are not designed to cut abrasive aggregate and may dull quickly. If you are drilling only two or three small holes into typical edging, a basic carbide round-shank bit is a sensible purchase. If it takes several minutes to make one shallow hole, or the tip is visibly worn, do not keep leaning on it. Replace the bit or use a rotary hammer.
For holes larger than about 1/2 inch, deep holes, or a long run of anchor points, a dedicated rotary hammer and matching SDS-Plus bits are usually more comfortable and productive than asking a small cordless hammer drill to do the same work. A cordless SDS-Plus rotary hammer is a substantial purchase, though, so renting one makes more sense for a one-time project. Measure twice, drill a test hole in a spare piece if possible, and stop if a crack appears or the stone shifts.