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Concrete with rebar nearby calls for two different decisions: choose a bit that suits the concrete, and stop before a standard masonry bit chews into steel. A carbide-tipped bit is usually the right purchase for ordinary holes. If the hole’s location or depth puts it at risk of hitting reinforcement, the better strategy is to detect and avoid the bar—not to assume any bit can drill through it safely.
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Choose the bit for the hole
For a few holes in a house wall or slab, a conventional carbide-tipped masonry bit is usually sufficient. Use it in a hammer drill, not an impact driver. A rotary hammer and SDS-plus bit make more sense for repeated drilling, larger diameters, or hard concrete: the hammering action is more efficient, and SDS shanks are designed for that tool. SDS bits do not fit an ordinary three-jaw drill chuck unless the tool has a compatible adapter, which is not a good substitute for an SDS chuck in demanding work.
Buy the diameter and working length specified for the anchor, not merely the largest bit your drill can accept. A hole that is too wide can leave an expansion anchor loose; one that is too shallow can prevent it from seating. For a typical small wall plug, the package gives the required bit diameter. For a concrete screw, follow the maker’s stated pilot-hole diameter and depth.
Compare carbide-tipped masonry bit sets if you need common sizes for occasional jobs. A basic set is fine for a handful of holes; premium bits are easier to justify when you drill often, work in hard aggregate, or need consistent hole dimensions.
Which bit and tool fit the job?
| Setup | Best use | Trade-off near rebar |
|---|---|---|
| Carbide masonry bit, hammer drill | Occasional anchor holes, commonly around 1/4 to 1/2 inch | Good value, but stop if the bit meets steel; hammering against rebar can damage the tip. |
| SDS-plus carbide bit, rotary hammer | Many holes, larger holes, or tougher concrete | Faster in concrete, not a rebar-cutting bit. The extra power can make it easier to damage a stuck bit. |
| Rebar-cutting bit or steel-cutting method | A bar must be crossed and the job permits it | Requires the right tool, size, and approval. Cutting reinforcement can compromise the structure. |
Locate reinforcement before drilling
Use a suitable scanner or rebar detector and mark the suspected bar lines before laying out holes. Check the scanner instructions: readings depend on material, cover depth, surface condition, and nearby metal. A detector is not a guarantee that a chosen spot is clear. If the hole is structural, near an edge, or part of an engineered connection, ask the responsible contractor or engineer before drilling. Never cut reinforcement in a structural slab, beam, or column just to make an anchor fit.
When the layout allows, move the hole several inches to one side of the detected bar and rescan. Keep required edge distances and spacing for the anchor; shifting a hole too close to a concrete edge can cause cracking or pullout. If the hole must be in a particular location, pause and confirm the reinforcement layout rather than forcing the bit through.
Drill without cooking the bit
Mark the depth with a stop collar or tape. Set the drill square to the surface, start slowly to keep the bit from walking, then use steady pressure. Let the hammer mechanism do the work. Excessive force slows the bit, overheats the carbide tip, and can make the hole wander. Pull the bit out periodically to clear concrete dust, especially in deeper holes. Clean the finished hole as the anchor maker directs; dust left behind can prevent proper setting or reduce bond strength.
Concrete dust is hazardous to breathe. Use a dust extractor or suitable collection shroud where possible, and wear eye protection and a properly fitted respirator appropriate for the dust. Check for pipes, wiring, and other embedded services as well as rebar. Do not drill blindly into a wall or slab simply because the surface looks clear.
If the bit hits rebar
A sudden stop, metallic scraping, or a polished steel spot in the hole can indicate contact with reinforcement. Release the trigger; do not lean harder on the drill or keep hammering. Continuing can blunt or chip the carbide tip, overheat the bit, enlarge the concrete around the bar, and leave an unusable hole. Back the bit out, inspect it, and verify the location with a scanner.
If moving the hole is acceptable, shift it and drill a new pilot hole. If crossing the bar is permitted, use a method specifically suited to steel and the required hole size, with the correct tool and guidance. A standard masonry bit is not meant to cut rebar. A rotary hammer bit may be faster in concrete, but it does not change that limitation. For a small anchor hole, relocation is commonly cheaper and safer than buying a specialized cutter.
Check concrete rebar detector options before starting when reinforcement is likely or the hole location is difficult to change. For frequent drilling, an SDS-plus setup can save time; for a few correctly placed anchor holes, a sharp carbide masonry bit in a hammer drill is usually enough.