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Concrete block is easier to drill than poured concrete, but the wrong bit can still skate across the face, overheat, or leave a hole too wide for the anchor. For most household jobs, a sharp carbide-tipped masonry bit and a hammer drill are the practical starting point. The right diameter, drilling method, and dust cleanup matter as much as the brand.
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Choose the right bit for the job
For a few holes for plastic anchors, a standard carbide-tipped masonry bit is usually enough. It has a blunt carbide cutting tip and flutes that carry dust out of the hole. Pair it with a hammer drill if available; in hammer mode, the bit rotates while the drill adds short impacts. A regular cordless drill can work in block, especially in the softer hollow sections, but it will be slower. Press steadily rather than forcing it.
Look for a bit with a round shank if your drill has a standard three-jaw chuck. SDS-Plus bits fit SDS-Plus rotary hammers, not ordinary chucks. Rotary hammers are useful for repeated holes, larger diameters, or hard spots such as block webs, but are excessive for a couple of small anchor holes. A carbide-tipped masonry bit set is a sensible choice when you need several common sizes.
Bit and drill options compared
| Setup | Best for | Trade-off |
|---|---|---|
| Carbide masonry bit in hammer drill | Most anchor holes and light mounting work | Slower than a rotary hammer in hard material |
| Carbide masonry bit in regular drill | A few small holes in soft block or near fragile surfaces | Slow in dense block; more pressure can make the bit wander or overheat |
| SDS-Plus bit in rotary hammer | Many holes, larger holes, or tough block webs | More tool and bit than occasional small jobs require |
Match the bit to the anchor
Use the hole diameter specified by the anchor maker, not a guess based on the screw. For example, a 1/4-inch masonry bit is common for some 1/4-inch plastic anchors, but anchor designs vary; check the package. If the hole is undersized, the anchor may not seat. If oversized, it can spin or pull out. Drill slightly deeper than the anchor—often about 1/4 inch extra—to leave room for dust and the tip of the screw.
For a small set of common sizes, buying a masonry bit assortment is cheaper than buying each size separately. Cheap sets are fine for occasional holes in ordinary block. They tend to dull sooner, and a bit that has been used on hard concrete may cut poorly even if its tip still looks intact. If you have many holes, choose a better-quality bit or an SDS-Plus set matched to your rotary hammer.
Drill the hole without damaging the block
Mark the location and check for wiring or plumbing before drilling. Avoid the very edge of a block and the mortar joint when possible: the face shell can chip, and mortar may crumble. If the hole must be near an edge, use a smaller pilot hole first and keep pressure light. A piece of painter’s tape can help mark the spot, though it will not make a worn bit cut accurately.
Set the bit square to the wall. Start at low speed without hammer action until the tip has made a shallow seat; then switch on hammer mode if needed. Keep the drill straight and let the tool do the work. Leaning hard on it can flex the bit, widen the hole, or crack a thin block face. Pull the bit out periodically to clear dust, especially in deeper holes. If it stops advancing, do not keep pushing until the shank gets hot: clear the hole, check that hammer mode is on, and inspect the tip for wear.
For fragile block or a small hole, begin without hammering and add it only if progress stalls. Hammer action is fast, but it can chip the entry or blow out the back of a thin face. When drilling through hollow block, the bit may suddenly break through into a cavity; ease off as it does. If the hole lands in a hollow cell, use an anchor designed for hollow masonry rather than assuming a standard plastic plug will hold.
Control dust and protect yourself
Masonry drilling produces fine silica-containing dust. Wear eye protection and a well-fitting respirator rated N95 or better, and keep other people away from the dust. Use a vacuum with suitable filtration at the hole if available, and follow local rules for silica dust. Do not blow dust out with your mouth. Before inserting an anchor, vacuum the hole or use a hand pump; loose dust can prevent full seating and reduce holding strength.
Stop if the bit wanders, the hole becomes ragged, or the drill and bit heat rapidly. A dull or overheated bit may still turn but cut poorly. Let it cool naturally rather than quenching it, which can damage the carbide joint. Replace it when the tip is rounded, chipped, or noticeably slower than a fresh bit.
What to buy
For a few shelf brackets or light fixtures, a standard carbide-tipped bit in the exact anchor size is usually the best-value purchase. A cordless hammer drill makes sense if block drilling is a recurring task, but it is not essential for occasional small holes in soft block. If you are drilling many larger holes, consider a set of SDS-Plus masonry bits only if you own or plan to buy a compatible rotary hammer.
Buy for the material and workload, not the biggest kit. One sharp bit in the correct diameter, used straight and cleared of dust, will usually outperform a large bargain set with the wrong size or worn tips.